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Key Message: The tomato Ty-6 gene conferring resistance against begomoviruses has been cloned and shown to be a variant of DNA polymerase delta subunit 1. Ty-6 is a major resistance gene of tomato that provides resistance against monopartite and bipartite begomoviruses. The locus was previously mapped on chromosome 10, and in this study, we fine-mapped Ty-6 to a region of 47 kb, including four annotated candidate genes. Via whole-genome resequencing of Ty-6 breeding lines and several susceptible breeding lines, the polymorphisms in gene sequences were discovered and gene-associated markers were developed for marker-assistant breeding. Further, virus-induced gene silencing and candidate gene overexpressing in susceptible tomatoes revealed that Ty-6-mediated resistance is controlled by Solyc10g081250, encoding the DNA polymerase delta subunit 1, SlPOLD1. The single nucleotide polymorphism of Ty-6 results in an amino acid change that might influence the fidelity of virus DNA replication., Competing Interests: Declarations. Conflict of interest: The authors declare no competing financial or non-financial interests in relation to the work described., (© 2025. The Author(s).)

This study aims to enhance sustainable disease management in black gram by identifying varieties resistant to Mungbean Yellow Mosaic India Virus (MYMIV). We screened sixteen black gram genotypes, assessing physiological, biochemical and enzymatic basis. Results revealed a range of resistance levels, with PANT URD-19 showing the highest resistance (PDI 0.47%) and Pejua the lowest (PDI 37.24%). Seven genotypes demonstrated strong resistance, highlighting the necessity for targeted breeding. Variations in leaf thickness, trichome density, stomatal frequency, and epicuticular wax content were significant, with resistant varieties like LBG-888 and PANT URD-19 exhibiting thicker leaves, higher trichome density, and more wax, correlating with reduced susceptibility. Chlorophyll content was higher in resistant varieties, while susceptible ones had reduced levels and increased sugar content, which may exacerbate MYMIV impact by attracting more whiteflies. Enzymatic analysis showed that resistant genotypes had elevated POD, SOD, and PAL activities, supporting their enhanced defense mechanisms. Multivariate analysis confirmed these findings, with leaf thickness, trichome density, and wax content negatively correlating with disease severity, while stomatal frequency and total sugar content were positively correlated. These results emphasize the potential of these traits in developing MYMIV-resistant black gram varieties and support the advancement of eco-friendly agricultural practices., Competing Interests: Declarations. Competing interests: The authors declare no competing interests. Ethical approval: Not applicable, as no approval of research ethics committees was required to accomplish the goals of this study because experimental work was conducted with an unregulated plant varieties., (© 2024. The Author(s).)

The traditional understanding of begomovirus transmission exclusively through the whitefly Bemisia tabaci (Gennadius) has shifted with findings of seed transmission in some begomoviruses over the last decade. We investigated the seed transmissibility of cucurbit leaf crumple virus (CuLCrV), a bipartite begomovirus that has recently emerged as a severe constraint for yellow squash ( Cucurbita pepo L.) production in the southeastern United States. We found a high concentration of CuLCrV in the male and female flower tissues of infected squash, including the pollen and ovules. The virus infiltrated the fruit tissues, including the endocarp and funiculus, which are anatomically positioned adjacent to the seeds. In seeds, CuLCrV was detected in the endosperm and embryo, where there are no vascular connections, in addition to the seed coat. The virus was detected in the radicle, plumule, cotyledonary leaves, and true leaves of seedlings grown from seeds collected from infected fruits. In the grow-out test conducted, CuLCrV infections ranged from 17 to 56% of the progeny plants. To ensure that partial viral genome fragments were not being mistaken for replicative forms of the virus, we performed rolling circle amplification PCR and amplified complete DNA-A and DNA-B of CuLCrV from seed tissues, seedlings, and progeny plants of CuLCrV-infected squash. Near-complete DNA-A and DNA-B sequences of CuLCrV were recovered from a progeny plant, further validating our findings. Our results demonstrate that CuLCrV can translocate from vegetative to reproductive tissues of yellow squash, persist within the seeds, and subsequently induce infection in progeny plants, confirming its capacity for seed transmission., Competing Interests: The author(s) declare no conflict of interest.

Two phylogenetically unrelated viruses transmitted by different insect vectors, tomato spotted wilt virus (TSWV) and tomato yellow leaf curl virus (TYLCV), are major threats to tomato and other vegetable production. Although co-infections of TSWV and TYLCV on the same host plant have been reported on numerous occasions, there is still lack of research attempting to elucidate the mechanisms underlying the relationship between two viruses when they coexist in the same tomato or other plants. After assessing the effect of four TSWV-coded proteins on suppressing TYLCV in TSWV N transgenic Nicotiana benthamiana seedlings, the TSWV N protein proved to be effective in reducing TYLCV quantity and viral symptoms. Western blot analysis indicated that TSWV N was involved in down-regulating the expression level of the V1, C3, and C4 proteins of TYLCV, among which V1 was the most significantly suppressed one. Moreover, TSWV N was confirmed to reduce TYLCV V1 within both nucleus and cytoplasm, but a greater suppression was observed in cytoplasm. The co-immunoprecipitation and mass spectrometry identified 244 differential proteins from the TYLCV-infected TSWV N transgenic N. benthamiana seedling. These proteins pertaining to energy metabolism pathways were enriched, suggesting that TSWV N could inhibit TYLCV through competing for energy or regulating energy-related metabolism. The evidence presented here offers a novel perspective that will facilitate a comprehensive understanding of virus-virus and virus-host interactions, as well as a potential strategy for plant virus control through using TSWV N in the near future., (© 2024 The Author(s). Molecular Plant Pathology published by British Society for Plant Pathology and John Wiley & Sons Ltd.)

Tomato yellow leaf curl virus (TYLCV) poses a significant threat to tomato production, leading to severe yield losses. The current control strategies primarily rely on the use of pesticides, which are often nonselective and costly. Therefore, there is an urgent need to identify more environmentally friendly alternatives. Dufulin, a novel compound that has been effective in controlling viral diseases in tobacco and rice, has not yet been tested against TYLCV. This study assessed the efficacy of dufulin in controlling TYLCV over a three-year span from 2021 to 2023 through field trials, by monitoring disease symptoms and viral titers. Additionally, this study assessed the expression levels of genes associated with systemic acquired resistance (SAR), specifically proteinase inhibitor II ( PI II ) and non-expressor of pathogenesis-related genes 1 ( NPR1 ), using real-time qRT-PCR. The chlorophyll and nitrogen content in the leaves were also measured. Plants treated with dufulin showed reduced symptomatology and lower viral titers compared to the controls. Analysis of gene expression revealed that NPR1 was upregulated in the dufulin-treated plants, whereas PI II expression was consistently downregulated in the TYLCV-infected plants. Interestingly, PI II expression increased in the healthy plants following a seven-day post-treatment with dufulin. Moreover, the treated plants exhibited a higher chlorophyll content than the controls, though no significant differences in the nitrogen levels were observed between the dufulin-treated and water-treated plants. Overall, the application of dufulin significantly bolstered the plant's defense response, effectively reducing TYLCV symptoms and enhancing resistance.

Background: Tomato (Solanum lycopersicum L.) is a widely cultivated crop in tropical regions, but its production is often hampered by significant losses attributed to diseases like tomato leaf curl virus (ToLCV), fusarium wilt and root-knot nematode., Methods and Results: This study employed an integrated approach utilizing both co-dominant and dominant SCAR markers, selected for specific resistance genes (ToLCV-Ty-1, Ty-2, Ty-2, Fusarium wilt (Race-2)-I-2, and Root-knot nematode-Mi-1. These markers with their specific gene of interest were used to screen the ten fresh market breeding lines of tomato. The P625 marker played a pivotal role in the identification process of Ty-3 alleles and effectively distinguishing between Ty-3a and Ty-3. I-2/5 (Fusarium wilt I-2), and Mi-23 (Root-knot nematode Mi-1) effectively identified and discriminated between heterozygous and homozygous states of specific genes. All resistant lines and a susceptible line for ToLCV (Ty-1, Ty-2, Ty-3), Fusarium wilt ((Race-2)- I-2) and Root-knot nematode underwent sequencing using specific primer pairs through the Sanger dideoxy technique. The resulting nucleotide sequences were aligned utilizing MEGA7 bioinformatic software and subjected to nucleotide BLAST in the NCBI database to determine sequence per cent identity and query cover, facilitating comparison with other submitted sequences., Conclusion: The determination of genomic positions for these nucleotide sequences may enable researchers to cartographically pinpoint the locations of genetic variations within the genome., Competing Interests: Declarations. Ethics approval: This article does not contain any studies with human participants or animals performed by any of the authors. Competing interests: The authors declare no competing interests., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

In nature, it is common for plants to be infected by multiple pathogens simultaneously, and deciphering the underlying mechanisms of such interactions has remained elusive. The occurrence of root-knot nematode (RKN), Meloidogyne incognita, and tomato yellow leaf curl virus (TYLCV; Begomovirus coheni) has been reported in most tomato cultivation areas. We investigated the interaction between RKN and TYLCV in tomato plants at phenotypic, biochemical, and gene expression levels. Several treatments were considered including mock inoculation, inoculation with TYLCV or RKN alone, simultaneous inoculation with both TYLCV and RKN, and sequential inoculations with a five-day interval. Among them, simultaneous inoculation showed the highest impact on RKN suppression compared to mock-inoculated plants. Biochemical assays in the time-point experiments demonstrated that the pick of defense capacity of plants occurs at 48- and 72-h post-inoculation. Gene expression analyses utilizing marker genes from main hormonal pathways involved in plant defense, including salicylic acid (SA), jasmonic acid (JA), and ethylene (ET), indicated that ET and SA are highly involved in the potentiation of TYLCV-induced defense against RKN. To validate the action of SA and ET in the induction of defense against RKN by TYLCV, transgenic lines deficient in SA (NahG) and ET (ACD) accumulation were co-inoculated with TYLCV and RKN. Both transgenic lines failed to express TYLCV-induced defense against RKN. These findings demonstrate an antagonistic effect of TYLCV against RKN in tomato plants, mediated by SA and ET signaling pathways., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Masoud Shams-bakhsh reports financial support was provided by Tarbiat Modares University. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Masson SAS. All rights reserved.)

Tomato yellow leaf curl virus disease has seriously threatened the quality and yield of tomatoes. In this study, we investigated the role of amiRNA technology in disease resistance in tomatoes (cherry tomato and large-fruited tomato) and analyzed the physiological and molecular mechanisms of disease resistance in transgenic plants. TYLCV contains six functional genes, of which the C 1, C2 , and V1 genes have more phosphorylation sites and glycosylation sites, and the protein structure is more complex. The virus replication was inhibited, the peroxidation of membrane lipids was reduced, and disease resistance was enhanced in all transgenic cherry tomato (J6) plants in which the C1 , C2 , and V1 genes were silenced, respectively. Similarly, silencing of the C1 gene enhanced disease resistance in large-fruited tomatoes. In conclusion, amiRNA technology hinders viral replication, leading to reduced activity of the tomato plant-pathogen interaction pathway and weakening tomato-virus interactions, thereby improving disease resistance.

Blackgram ( Vigna mungo L. Hepper) production is hindered by mungbean yellow mosaic virus (MYMV) with disease incidence up to 85% in hot spot locations of Tamil Nadu, India. Field screening of 50 genotypes identified Mash 114 as resistant and CO 5 as susceptible cultivars. To understand the resistance mechanism, temporal metabolome variations of resistant (RC) and susceptible (SC) cultivars were assessed at 3, 6, and 12 days post-inoculation with MYMV via whitefly transmission using GC-MS. The study included aviruliferous whitefly and healthy controls. Data analysis identified 98 differential compounds across various metabolic groups. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) revealed distinct metabolic profiles, with RC accumulating antiviral terpenoids such as ursolic acid, betulin, and umbelliprenin, while SC upregulated lipids and fatty acids favoring virus replication. These findings provide insights for breeders to identify resistant sources and pave the way for improved MYMV management strategies using antiviral products.

Whiteflies (Bemisia tabaci) and the diseases they transmit are a major detriment to crop yields and a significant contributor to world hunger. The highly evolved interactions of host plant, phloem-feeding insect vector with endosymbionts and persistently transmitted virus represent a tremendous challenge for interdisciplinary study. Presented here is the establishment of a colony of axenic whiteflies on tissue-cultured plants. Efficient colony establishment was achieved by a surface sterilization of eggs laid on axenic phototrophically tissue-cultured plants. The transfer of emerging whiteflies through coupled tissue culture vessels to new axenic plants facilitates robust subculturing and produces hundreds of whitefly adults per month. Whitefly proliferation on more than two dozen plant species is shown as well as in vitro testing of whitefly preference for different plants. This novel multi-organism system provides the high-level of biocontainment required by Federal permitting to conduct virus transmission experiments. Axenic whitefly adults were able to acquire and transmit a begomovirus into tissue-cultured plants, indicating that culturable gut microorganisms are not required for virus transmission. The approach described enables a wide range of hypotheses regarding whitefly phytopathology without the expense, facilities, and contamination ambiguity associated with current approaches., Competing Interests: Declarations Competing interests The authors declare no competing interests., (© 2024. The Author(s).)

Geminiviruses infect numerous crops and cause extensive agricultural losses worldwide. During viral infection, geminiviral C4/AC4 proteins relocate from the plasma membrane to chloroplasts, where they inhibit the production of host defense signaling molecules. However, mechanisms whereby C4/AC4 proteins are transported to chloroplasts are unknown. We report here that tomato (Solanum lycopersicum) COAT PROTEIN COMPLEX I (COPI) components play a critical role in redistributing Tomato yellow leaf curl virus C4 protein to chloroplasts via an interaction between the C4 and β subunit of COPI. Coexpression of both proteins promotes the enrichment of C4 in chloroplasts that is blocked by a COPI inhibitor. Overexpressing or downregulating gene expression of COPI components promotes or inhibits the viral infection, respectively, suggesting a proviral role of COPI components. COPI components play similar roles in C4/AC4 transport and infections of two other geminiviruses: Beet curly top virus and East African cassava mosaic virus. Our results reveal an unconventional role of COPI components in protein trafficking to chloroplasts during geminivirus infection and suggest a broad-spectrum antiviral strategy in controlling geminivirus infections in plants., Competing Interests: Conflict of interest statement. None declared., (Published by Oxford University Press on behalf of American Society of Plant Biologists 2024.)

Hemipteran insects transmit viruses when infesting plants, during which vectors activate salicylic acid (SA)-regulated antiviral defenses. How vector-borne plant viruses circumvent these antiviral defenses is largely unexplored. During co-infections of begomoviruses and betasatellites in plants, betasatellite-encoded βC1 proteins interfere with SA signaling and reduce the activation of antiviral resistance. βC1 inhibits SA-induced degradation of NbNPR3 (Nicotiana benthamiana nonexpressor of pathogenesis-related genes 3), a negative regulator of SA signaling. βC1 does not bind directly to NbNPR3, but regulates NbNPR3 degradation via heat shock protein 90s (NbHSP90s). NbHSP90s bind to both NbNPR3 and βC1 and suppress SA signaling. This viral success strategy appears to be conserved as it is also documented for viral proteins encoded by two aphid-borne viruses. Our findings reveal an exquisite mechanism that facilitates the persistence of vector-borne plant viruses and provide important insights into the intricacies of the virus life cycle., (© 2024. The Author(s).)

Plant viruses exist in a broader ecological community that includes non-vector herbivores that can impact vector abundance, behavior, and virus transmission within shared host plants. However, little is known about the effects of non-vector herbivore infestation on virus transmission by vector insects on neighboring plants through inter-plant airborne chemicals. In this study, we investigated how volatiles emitted from tomato plants infested with the two-spotted spider mite (Tetranychus urticae) affect the infection of neighboring plants by tomato yellow leaf curl virus (TYLCV) transmitted by whitefly (Bemisia tabaci). Exposure of neighboring tomato plants to volatiles released from T. urticae-infested tomato plants reduced subsequent herbivory as well as TYLCV transmission and infection, and the jasmonic acid signaling pathway was essential for generation of the inter-plant defense signals. We also demonstrated that (E)-β-ocimene and methyl salicylic acid were two volatiles induced by T. urticae that synergistically attenuated TYLCV transmission and infection in tomato. Thus, our findings suggest that plant-plant communication via volatiles likely represents a widespread defensive mechanism that substantially contributes to plant fitness. Understanding such phenomena may help us to predict the occurrence and epidemics of multiple herbivores and viruses in agroecosystems, and ultimately to manage pest and virus outbreaks., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

The majority of plant viruses rely on insect vectors for inter-plant transmission. Amid virus transmission, vector-borne viruses such as begomoviruses may significantly modulate host plants in various ways and, in turn, plant palatability to insect vectors. While many case studies on monopartite begomoviruses are available, bipartite begomoviruses are understudied. More importantly, detailed elucidation of the molecular mechanisms involved is limited. Here, we report the mechanisms by which an emerging bipartite begomovirus, the Sri Lankan cassava mosaic virus (SLCMV), modulates plant defenses against whitefly. SLCMV infection of tobacco ( Nicotiana tabacum ) plants significantly downregulated defenses against whitefly, as whitefly survival and fecundity increased significantly on virus-infected plants when compared to the controls. We then profiled SLCMV-induced transcriptomic changes in plants and identified a repertoire of differentially expressed genes (DEGs). GO enrichment analysis of DEGs demonstrated that the term defense response was significantly enriched. Functional analysis of DEGs associated with defense response revealed that four downregulated DEGs, including putative late blight resistance protein homolog R1B-17 ( R1B-17 ), polygalacturonase inhibitor-like ( PGI ), serine/threonine protein kinase CDL1-like ( CDL1 ), and Systemin B , directly contributed to plant defenses against whitefly. Taken together, our findings elucidate the role of novel plant factors involved in the modulation of plant defenses against whitefly by a bipartite begomovirus and shed new light on insect vector-virus-host plant tripartite interactions.

Yellow mosaic disease (YMD) is a major constraint for the low productivity of mungbean, mainly in South Asia. Addressing this issue requires a comprehensive approach, integrating field and challenge inoculation evaluations to identify effective solutions. In this study, an infectious clone of Begomovirus vignaradiataindiaense (MYMIV) was developed to obtain a pure culture of the virus and to confirm resistance in mungbean plants exhibiting resistance under natural field conditions. The infectivity and efficiency of three Agrobacterium tumefaciens strains (EHA105, LBA4404, and GV3101) were evaluated using the susceptible mungbean genotype PS16. Additionally, a recombinant inbred line (RIL) population comprising 175 lines derived from Pusa Baisakhi (MYMIV susceptible) and PMR-1 (MYMIV resistant) cross was developed and assessed for YMD response. Among the tested Agrobacterium tumefaciens strains, EHA105 exhibited the highest infectivity (84.7%), followed by LBA4404 (54.7%) and GV3101 (9.80%). Field resistance was evaluated using the coefficient of infection (CI) and area under disease progress curve (AUDPC), identifying seven RILs with consistent resistant reactions (CI≤9) and low AUDPC (≤190). Upon challenge inoculation, six RILs exhibited resistance, while RIL92 displayed a resistance response, with infection occurring in less than 10% of plants after 24 to 29 days post inoculation (dpi). Despite some plants remaining asymptomatic, MYMIV presence was confirmed through specific PCR amplification of the MYMIV coat protein (AV1) gene. Quantitative PCR revealed a very low relative viral load (0.1-5.1% relative fold change) in asymptomatic RILs and the MYMIV resistant parent (PMR1) compared to the susceptible parent (Pusa Baisakhi). These findings highlight the potential utility of the developed infectious clone and the identified MYMIV-resistant RILs in future mungbean breeding programs aimed at cultivating MYMIV-resistant varieties., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Kumari et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Background: Tomato leaf curl New Delhi virus (ToLCNDV) (family Geminiviridae, genus Begomovirus) is a significant threat to cucumber (Cucumis sativus) production in many regions. Previous studies have reported the genetic mapping of loci related to ToLCNDV resistance, but no resistance genes have been identified., Results: We conducted map-based cloning of the ToLCNDV resistance gene in cucumber accession No.44. Agroinfiltration and graft-inoculation analyses confirmed the resistance of No.44 to ToLCNDV isolates from the Mediterranean and Asian countries. Initial mapping involving two rounds of phenotyping with two independent F 2 populations generated by crossing the begomovirus-susceptible cultivar SHF and No.44 consistently detected major quantitative trait loci (QTLs) on chromosomes 1 and 2 that confer resistance to ToLCNDV. Fine-mapping of Cy-1, the dominant QTL on chromosome 1, using F 3 populations narrowed the candidate region to a 209-kb genomic segment harboring 24 predicted genes. Among these genes, DFDGD-class RNA-dependent RNA polymerase (CsRDR3), an ortholog of Ty-1/Ty-3 of tomato and Pepy-2 of capsicum, was found to be a strong candidate conferring ToLCNDV resistance. The CsRDR3 sequence of No.44 contained multiple amino acid substitutions; the promoter region of CsRDR3 in No.44 had a large deletion; and the CsRDR3 transcript levels were greater in No.44 than in SHF. Virus-induced gene silencing (VIGS) of CsRDR3 using two chromosome segment substitution lines harboring chromosome 1 segments derived from No.44 compromised resistance to ToLCNDV., Conclusions: Forward and reverse genetic approaches identified CsRDR3, which encodes a DFDGD-class RNA-dependent RNA polymerase, as the gene responsible for ToLCNDV resistance at the major QTL Cy-1 on chromosome 1 in cucumber. Marker-assisted breeding of ToLCNDV resistance in cucumber will be expedited by using No.44 and the DNA markers developed in this study., (© 2024. The Author(s).)

Common bean ( Phaseolus vulgaris L.) is a widely cultivated crop, representing an important protein source in the human diet in developing countries. The production of this crop faces serious challenges, such as virus diseases transmitted by the whitefly Bemisia tabaci . Although there is a lot of information about some of these viruses, most of what we know has been developed using model systems, such as tomato plants and tomato yellow leaf curl virus (TYLCV). There is still very little information on the most relevant common bean viruses, such as bean golden mosaic virus (BGMV), bean golden yellow mosaic virus (BGYMV), bean dwarf mosaic virus (BDMV), cowpea mild mottle virus (CPMMV), and bean yellow disorder virus (BnYDV). In this review, we discuss the available data in the most up-to-date literature and suggest future research avenues to contribute to the development of management tools for preventing or reducing the damage caused by viruses in this important crop.

Insect vector-virus-plant interactions have important ecological and evolutionary implications. The constant struggle of plants against viruses and insect vectors has driven the evolution of multiple defense strategies in the host as well as counter-defense strategies in the viruses and insect vectors. Cotton leaf curl Multan virus (CLCuMuV) is a major causal agent of cotton leaf curl disease in Asia and is exclusively transmitted by the whitefly Bemisia tabaci. Here, we report that plants infected with CLCuMuV and its betasatellite CLCuMuB enhance the performance of the B. tabaci vector, and βC1 encoded by CLCuMuB plays an important role in begomovirus-whitefly-tobacco tripartite interactions. We showed that CLCuMuB βC1 suppresses the jasmonic acid signaling pathway by interacting with the subtilisin-like protease 1.7 (NtSBT1.7) protein, thereby enhancing whitefly performance on tobacco plants. Further studies revealed that in wild-type plants, NtSBT1.7 could process tobacco preprohydroxyproline-rich systemin B (NtpreproHypSysB). After CLCuMuB infection, CLCuMuB βC1 could interfere with the processing of NtpreproHypSysB by NtSBT1.7, thereby impairing plant defenses against whitefly. These results contribute to our understanding of tripartite interactions among virus, plant, and whitefly, thus offering ecological insights into the spread of vector insect populations and the prevalence of viral diseases., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Tomato yellow leaf curl virus (TYLCV), a DNA virus belonging to the genus Begomovirus, significantly impedes the growth and development of numerous host plants, including tomatoes and peppers. Due to its rapid mutation rate and frequent recombination events, achieving complete control of TYLCV proves exceptionally challenging. Consequently, identifying resistance mechanisms become crucial for safeguarding host plants from TYLCV-induced damage. This review article delves into the global distribution, dispersal patterns, and defining characteristics of TYLCV. Moreover, the intricate interplay between TYLCV and various influencing factors, such as insect vectors, susceptible host plants, and abiotic stresses, plays a pivotal role in plant-TYLCV interactions. The review offers an updated perspective on recent investigations focused on plant response mechanisms to TYLCV infection, including the intricate relationship between TYLCV, whiteflies, and regulatory factors. This comprehensive analysis aims to establish a foundation for future research endeavors exploring the molecular mechanisms underlying TYLCV infection and the development of plant resistance through breeding programs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Masson SAS.)

The sweetpotato whitefly, Bemisia tabaci MEAM1, is one of the most devastating pests of row-crop vegetables worldwide, damaging crops directly through feeding and indirectly through the transmission of many different viruses, including the geminivirus Tomato yellow leaf curl virus (TYLCV). Y-tube olfactometer tests were conducted at different stages of TYLCV infection in tomatoes to understand how TYLCV affects B. tabaci behavior. We also recorded changes in tomato hosts' color and volatile profiles using color spectrophotometry and gas chromatography-mass spectrometry (GC-MS). We found that the infection status of B . tabaci and the infection stage of TYLCV influenced host selection, with uninfected whiteflies showing a preference for TYLCV-infected hosts, especially during the late stages of infection. Viruliferous B. tabaci attraction to visual targets significantly differed from non-viruliferous B. tabaci . Late-stage infected hosts had larger surface areas reflecting yellow-green wavelengths and higher emissions of methyl salicylate in their volatile profiles. These findings shed new light on several critical mechanisms involved in the viral manipulation of an insect vector and its economically important host., Competing Interests: The authors declare there are no competing interests., (©2024 Paris et al.)

Begomoviruses have emerged as destructive pathogens of crops, particularly in the tropics and subtropics, causing enormous economic losses and threatening food security. Epidemics caused by begomoviruses have even spread in regions and crops that were previously free from these viruses. The most seriously affected crops include cassava; cotton; grain legumes; and cucurbitaceous, malvaceous, and solanaceous vegetables. Alphasatellites, betasatellites, and deltasatellites are associated with the diseases caused by begomoviruses, but begomovirus-betasatellite complexes have played significant roles in the evolution of begomoviruses, causing widespread epidemics in many economically important crops throughout the world. This article provides an overview of the evolution, distribution, and approaches used by betasatellites in the suppression of host plant defense responses and increasing disease severity.

Key Message: The investigation of MYMIV-infected mung bean leaf apoplast revealed viral genome presence, increased EVs secretion, and altered stress-related metabolite composition, providing comprehensive insights into plant-virus interactions. The apoplast, an extracellular space around plant cells, plays a vital role in plant-microbe interactions, influencing signaling, defense, and nutrient transport. While the involvement of apoplast and extracellular vesicles (EVs) in RNA virus infection is documented, the role of the apoplast in plant DNA viruses remains unclear. This study explores the apoplast's role in mungbean yellow mosaic India virus (MYMIV) infection. Our findings demonstrate the presence of MYMIV genomic components in apoplastic fluid, suggesting potential begomovirus cell-to-cell movement via the apoplast. Moreover, MYMIV infection induces increased EVs secretion into the apoplast. NMR-based metabolomics reveals altered metabolic profiles in both apoplast and symplast in response to MYMIV infection, highlighting key metabolites associated with stress and defense mechanisms. The data show an elevation of α- and β-glucose in both apoplast and symplast, suggesting a shift in glucose utilization. Interestingly, this increase in glucose does not contribute to the synthesis of phenolic compounds, potentially influencing the susceptibility of mung bean to MYMIV. Fructose levels increase in the symplast, while apoplastic sucrose levels rise significantly. Symplastic aspartate levels increase, while proline exhibits elevated concentration in the apoplast and reduced concentration in the cytosol, suggesting a role in triggering a hypersensitive response. These findings underscore the critical role of the apoplast in begomovirus infection, providing insights for targeted viral disease management strategies., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Cotton (Gossypium hirsutum) is an economically potent crop in many countries including Pakistan, India, and China. For the last three decades, cotton production is under the constant stress of cotton leaf curl disease (CLCuD) caused by begomoviruses/satellites complex that is transmitted through the insect pest, whitefly (Bemisia tabaci). In 2018, we identified a highly recombinant strain; Cotton leaf curl Multan virus-Rajasthan (CLCuMuV-Raj), associated with the Cotton leaf curl Multan betasatellite-Vehari (CLCuMuB Veh ). This strain is dominant in cotton-growing hub areas of central Punjab, Pakistan, causing the third epidemic of CLCuD. In the present study, we have explored the CLCuD diversity from central to southern districts of Punjab (Faisalabad, Lodhran, Bahawalpur, Rahimyar Khan) and the major cotton-growing region of Sindh (Tandojam), Pakistan for 2 years (2020-2021). Interestingly, we found same virus (CLCuMuV-Raj) and associated betasatellite (CLCuMuB Veh ) strain that was previously reported with the third epidemic in the central Punjab region. Furthermore, we found minor mutations in two genes of CLCuMuV-Raj C4 and C1 in 2020 and 2021 respectively as compared to its isolates in 2018, which exhibited virus evolution. Surprisingly, we did not find these mutations in CLCuMuV-Raj isolates identified from Sindh province. The findings of the current study represent the stability of CLCuMuV-Raj and its spread toward the Sindh province where previously Cotton leaf curl Kokhran virus (CLCuKoV) and Cotton leaf curl Shahdadpur virus (CLCuShV) have been reported. The findings of the current study demand future research on CLCuD complex to explore the possible reasons for prevalence in the field and how the virus-host-vector compatible interaction can be broken to develop resistant cultivars., (© 2024. The Author(s).)

Key Message: Unraveling genetic markers for MYMIV resistance in urdbean, with 8 high-confidence marker-trait associations identified across diverse environments, provides crucial insights for combating MYMIV disease, informing future breeding strategies. Globally, yellow mosaic disease (YMD) causes significant yield losses, reaching up to 100% in favorable environments within major urdbean cultivating regions. The introgression of genomic regions conferring resistance into urdbean cultivars is crucial for combating YMD, including resistance against mungbean yellow mosaic India virus (MYMIV). To uncover the genetic basis of MYMIV resistance, we conducted a genome-wide association study (GWAS) using three multi-locus models in 100 diverse urdbean genotypes cultivated across six individual and two combined environments. Leveraging 4538 high-quality single nucleotide polymorphism (SNP) markers, we identified 28 unique significant marker-trait associations (MTAs) for MYMIV resistance, with 8 MTAs considered of high confidence due to detection across multiple GWAS models and/or environments. Notably, 4 out of 28 MTAs were found in proximity to previously reported genomic regions associated with MYMIV resistance in urdbean and mungbean, strengthening our findings and indicating consistent genomic regions for MYMIV resistance. Among the eight highly significant MTAs, one localized on chromosome 6 adjacent to previously identified quantitative trait loci for MYMIV resistance, while the remaining seven were novel. These MTAs contain several genes implicated in disease resistance, including four common ones consistently found across all eight MTAs: receptor-like serine-threonine kinases, E3 ubiquitin-protein ligase, pentatricopeptide repeat, and ankyrin repeats. Previous studies have linked these genes to defense against viral infections across different crops, suggesting their potential for further basic research involving cloning and utilization in breeding programs. This study represents the first GWAS investigation aimed at identifying resistance against MYMIV in urdbean germplasm., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Disease resistance gene (R gene)-encoded nucleotide-binding leucine-rich repeat proteins (NLRs) are critical players in plant host defence mechanisms because of their role as receptors that recognise pathogen effectors and trigger plant effector-triggered immunity (ETI). This study aimed to determine the putative role of a cassava coiled-coil (CC)-NLR (CNL) gene MeRPPL1 ( Manes.12G091600 ) (single allele) located on chromosome 12 in the tolerance or susceptibility to South African cassava mosaic virus (SACMV), one of the causal agents of cassava mosaic disease (CMD). A transient protoplast system was used to knock down the expression of MeRPPL1 by clustered regularly interspaced short palindromic repeats-CRISPR-associated protein 9 (CRISPR-Cas9). The MeRPPL1 -targeting CRISPR vectors and/or SACMV DNA A and DNA B infectious clones were used to transfect protoplasts isolated from leaf mesophyll cells from the SACMV-tolerant cassava ( Manihot esculenta ) cultivar TME3. The CRISPR/Cas9 silencing vector significantly reduced MeRPPL1 expression in protoplasts whether with or without SACMV co-infection. Notably, SACMV DNA A replication was higher in protoplasts with lower MeRPPL1 expression levels than in non-silenced protoplasts. Mutagenesis studies revealed that protoplast co-transfection with CRISPR- MeRPPL1 silencing vector + SACMV and transfection with only SACMV induced nucleotide substitution mutations that led to altered amino acids in the highly conserved MHD motif of the MeRPPL1 -translated polypeptide. This may abolish or alter the regulatory role of the MHD motif in controlling R protein activity and could contribute to the increase in SACMV-DNA A accumulation observed in MeRPPL1 -silenced protoplasts. The results herein demonstrate for the first time a role for a CNL gene in tolerance to a geminivirus in TME3.

Sri Lankan cassava mosaic virus (SLCMV) is a prominent causative agent of cassava mosaic disease in Asia and relies on the whitefly Bemisia tabaci cryptic complex for its transmission. However, the molecular mechanisms involved in SLCMV transmission by B. tabaci have yet to be understood. In this study, we identified an aminopeptidase N-like protein (BtAPN) in B. tabaci Asia II 1, an efficient vector of SLCMV, which is involved in the SLCMV transmission process. Through the use of glutathione S-transferase pull-down assay and LC-MS/MS analysis, we demonstrated the interaction between BtAPN and the coat protein (CP) of SLCMV. This interaction was further confirmed in vitro, and we observed an induction of BtAPN gene expression following SLCMV infection. By interfering with the function of BtAPN, the quantities of SLCMV were significantly reduced in various parts of B. tabaci Asia II 1, including the whole body, midgut, hemolymph, and primary salivary gland. Furthermore, we discovered that BtAPN is conserved in B. tabaci Middle East-Asia Minor 1 (MEAM1) and interacts with the CP of tomato yellow leaf curl virus (TYLCV), a begomovirus known to cause severe damage to tomato production. Blocking BtAPN with antibody led to a significant reduction in the quantities of TYLCV in whitefly whole body and organs/tissues. These results demonstrate that BtAPN plays a generic role in interacting with the CP of begomoviruses and positively regulates their acquisition by the whitefly., (© 2024 The Authors. Insect Science published by John Wiley & Sons Australia, Ltd on behalf of Institute of Zoology, Chinese Academy of Sciences.)

Plants can respond to insect infestation and virus infection by inducing plant defenses, generally mediated by phytohormones. Moreover, plant defenses alter host quality for insect vectors with consequences for the spread of viruses. In agricultural settings, other organisms commonly interact with plants, thereby inducing plant defenses that could affect plant-virus-vector interactions. For example, plant defenses induced by omnivorous insects can modulate insect behavior. This study focused on tomato yellow leaf curl virus (TYLCV), a plant virus of the family Geminiviridae and genus Begomovirus . It is transmitted in a persistent circulative manner by the whitefly Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae), posing a global threat to tomato production. Mirids (Hemiptera: Miridae) are effective biological control agents of B. tabaci , but there is a possibility that their omnivorous nature could also interfere with the process of virus transmission. To test this hypothesis, this study first addressed to what extent the mirid bug Dicyphus hesperus Knight induces plant defenses in tomato. Subsequently, the impact of this plant-omnivore interaction on the transmission of TYLCV was evaluated. Controlled cage experiments were performed in a greenhouse setting to evaluate the impact of mirids on virus transmission and vector acquisition by B. tabaci. While we observed a reduced number of whiteflies settling on plants exposed to D. hesperus , the plant defenses induced by the mirid bug did not affect TYLCV transmission and accumulation. Additionally, whiteflies were able to acquire comparable amounts of TYLCV on mirid-exposed plants and control plants. Overall, the induction of plant defenses by D. hesperus did not influence TYLCV transmission by whiteflies on tomato.

A mandatory tomato-free period (TFP) was implemented in the state of Goiás, Brazil, in 2007 to help manage diseases caused by whitefly-transmitted begomoviruses. The impact of the TFP was examined in five locations across three states in Central Brazil from 2013 to 2016. Surveys revealed significant differences in begomovirus disease incidence among locations, i.e., low in Guaíra-TFP and Patos de Minas-TFP; moderate-high in Itaberaí-TFP and Morrinhos-TFP; and high in the non-TFP (NTFP) control, Cristalina-NTFP. PCR tests and DNA sequencing were used to validate the symptoms and showed that all collected symptomatic plant samples were infected with tomato severe rugose virus (ToSRV), a common indigenous bipartite begomovirus. Early season surveys (20 to 40 days after transplants [DAT]) in Itaberaí-TFP and Morrinhos-TFP revealed significantly less begomovirus disease in fields established sooner after the TFP (0 to 2 months) compared with incidences in (i) equivalent early planted fields in the Cristalina-NTFP control and (ii) fields established longer after the end of the TFP (>2 to 5 months). Whitefly infestation of crops was detected year-round in all locations and years, and all tested adults were classified in the Bemisia tabaci MEAM1 cryptic species. Infestation levels were significantly higher during the summer but did not vary significantly among locations. Results of monthly monitoring of adult whiteflies for general begomovirus and ToSRV were positively correlated and were indicators of disease incidence in the field. Notably, ToSRV was not detected in whiteflies collected from nontomato plants during the TFP, and there was a longer lag period before detection in whiteflies collected from processing tomatoes for Itaberaí-TFP and Morrinhos-TFP compared with Cristalina-NTFP. Taken together with the low levels of ToSRV infection detected in potential nontomato reservoir hosts at all locations, our results revealed low levels of primary inoculum during the TFP. Thus, even in a complex agroecosystem with year-round whitefly infestation of crops, the TFP was beneficial due to delayed and reduced begomovirus disease pressure during a critical stage of plant development (first month) and for favoring low levels of primary inoculum. Thus, we concluded that the TFP should be part of a regional integrated pest management (IPM) program targeting ToSRV in Brazil., Competing Interests: The author(s) declare no conflict of interest.

Background: Tomato (Solanum lycopersicum L.) is an economically important vegetable crop around the globe. Tomato yellow leaf curling (TYLC) is the most devastating viral disease posing a serious threat to tomato production throughout the tropical and subtropical world. Induction of microbe-mediated systemic resistance in plants has been of great interest in recent years as a novel microbiological tool in disease and insect pest management. This in-vitro study aimed to determine the effectiveness of different strains (BB252, BB72 and ARSEF-2860) of a hypocreal fungus Beauveria bassiana against TYLCV disease and aphid Myzus persicae. Potted tomato plants exogenously treated with conidial and filtrate suspensions of B. bassiana strains and of their partially purified or purified proteins were exposed to TYLCV inoculum and aphid M. persicae., Results: Results showed a significant suppression of TYLCV disease severity index by the exogenous application of conidial, filtrate and protein treatments of all B. bassiana strains and this response was directly proportional to the treatment concentration. Similarly, mean fecundity rate of M. persicae was also significantly reduced by the highest concentration of ARSEF-2860-derived elicitor protein PeBb1, followed by the highest concentrations of BB252- and BB72-derived partially purified proteins. Moreover, these B. bassiana-derived proteins also caused a significant upregulation of most of the plant immune marker genes associated with plant defense., Conclusion: Overall, the study findings suggest that these B. bassiana strains and their partially purified or purified elicitor proteins could be effective biological tools for the management of TYLCV and aphid infestation on tomato plants. © 2023 Society of Chemical Industry., (© 2023 Society of Chemical Industry.)

Tomato yellow leaf curl disease (TYLCD), caused by Tomato yellow leaf curl virus (TYLCV), is one of the most destructive diseases in tomato cultivation. By comparing the phenotypic characteristics and virus quantities in the susceptible variety 'Cooperation 909 Red Tomatoes' and the resistant variety 'Huamei 204' after inoculation with TYLCV infectious clones, our study discovered that the root, stem and leaf growth of the susceptible variety 'Cooperation 909 Red Tomatoes' were severely hindered and the resistant variety 'Huamei 204' showed growth inhibition only in roots. TYLCV accumulation in roots were significantly higher than in leaves. Further, we examined the expression of key genes in the SA and JA signalling pathways in leaves, stems and roots and found the up-regulation of SA-signalling genes in all organs of the susceptible variety after inoculation with TYLCV clones. Interestingly, SlJAZ2 in roots of the resistant variety was significantly down-regulated upon TYLCV infection. Further, we silenced the SlNPR1 and SlCOI1 genes individually using virus induced gene silencing system in tomato plants. We found that viruses accumulated to a higher level in SlNPR1 silenced plants than wild type plants, and the virus quantity in roots was significantly increased in SlCOI1 silenced plants. These results provide new insights for advancing research in understanding tomato-TYLCV interaction., Competing Interests: Declaration of Competing Interest The authors declare that we have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Background: Geminiviruses are DNA plant viruses that cause highly damaging diseases affecting crops worldwide. During the infection, geminiviruses hijack cellular processes, suppress plant defenses, and cause a massive reprogramming of the infected cells leading to major changes in the whole plant homeostasis. The advances in sequencing technologies allow the simultaneous analysis of multiple aspects of viral infection at a large scale, generating new insights into the molecular mechanisms underlying plant-virus interactions. However, an integrative study of the changes in the host transcriptome, small RNA profile and methylome during a geminivirus infection has not been performed yet. Using a time-scale approach, we aim to decipher the gene regulation in tomato in response to the infection with the geminivirus, tomato yellow leaf curl virus (TYLCV)., Results: We showed that tomato undergoes substantial transcriptional and post-transcriptional changes upon TYLCV infection and identified the main altered regulatory pathways. Interestingly, although the principal plant defense-related processes, gene silencing and the immune response were induced, this cannot prevent the establishment of the infection. Moreover, we identified extra- and intracellular immune receptors as targets for the deregulated microRNAs (miRNAs) and established a network for those that also produced phased secondary small interfering RNAs (phasiRNAs). On the other hand, there were no significant genome-wide changes in tomato methylome at 14 days post infection, the time point at which the symptoms were general, and the amount of viral DNA had reached its maximum level, but we were able to identify differentially methylated regions that could be involved in the transcriptional regulation of some of the differentially expressed genes., Conclusion: We have conducted a comprehensive and reliable study on the changes at transcriptional, post-transcriptional and epigenetic levels in tomato throughout TYLCV infection. The generated genomic information is substantial for understanding the genetic, molecular and physiological changes caused by TYLCV infection in tomato., (© 2023. The Author(s).)

Importance: Many plant viruses are transmitted by insect vectors in a circulative manner. For efficient transmission, the entry of the virus from vector hemolymph into the primary salivary gland (PSG) is a step of paramount importance. Yet, vector components mediating virus entry into PSG remain barely characterized. Here, we demonstrate the role of clathrin-mediated endocytosis and early endosomes in begomovirus entry into whitefly PSG. Our findings unravel the key components involved in begomovirus transport within the whitefly body and transmission by their whitefly vectors and provide novel clues for blocking begomovirus transmission., Competing Interests: The authors declare no conflict of interest.

Background: The whitefly, Bemisia tabaci (Gennadius) is one of the most economically important pests that cause serious damage to agricultural production by transmitting plant pathogenic viruses. Approximately 90% of the virus species transmitted by the whitefly are members of the genus begomovirus. Ramie mosaic virus (RaMoV) is a new bipartite begomovirus that causes severe damage to ramie and several other economic crops in China. In previous studies, we have demonstrated that RaMoV had no obvious direct or indirect effects on B. tabaci. However, whether B. tabaci affects RaMoV infection and the molecular mechanisms of their interaction remain unclear., Results: Here, we identified a zinc finger protein 330 (ZNF330) in B. tabaci MED interacted with the coat protein (CP) of RaMoV by the yeast two-hybrid assay. Then the interaction between ZNF330 and RaMoV CP was further verified by glutathione S-transferase (GST) pull-down assay. The expression of ZNF330 gene was continuously induced after RaMoV infection. ZNF330 negatively regulated RaMoV replication in the B. tabaci MED. Furthermore, the longevity and fecundity of RaMoV-infected female adults were significantly decreased after silencing of ZNF330., Conclusions: Our results indicated that the ZNF330 protein was involved in the negative regulation of RaMoV replication in the B. tabaci MED. High viral accumulation caused by ZNF330 silencing is detrimental to fecundity and longevity of the B. tabaci MED. These findings provided a new insight into identifying the binding partners in whitefly with viral CP and fully understanding the complex interactions between begomoviruses and their whitefly vector. © 2023 Society of Chemical Industry., (© 2023 Society of Chemical Industry.)

RNA-dependent RNA polymerases (RDRs) are key players in the antiviral defence mediated by RNA silencing in plants. RDR6 is one of the major components of the process, regulating the infection of certain RNA viruses. To better clarify its function against DNA viruses, we analyzed the effect of RDR6 inactivation (RDR6i) in N. benthamiana plants on two phloem-limited begomoviruses, the bipartite Abutilon mosaic virus (AbMV) and the monopartite tomato yellow leaf curl Sardinia virus (TYLCSV). We observed exacerbated symptoms and DNA accumulation for the New World virus AbMV in RDR6i plants, varying with the plant growth temperature (ranging from 16 °C to 33 °C). However, for the TYLCSV of Old World origin, RDR6 depletion only affected symptom expression at elevated temperatures and to a minor extent; it did not affect the viral titre. The accumulation of viral siRNA differed between the two begomoviruses, being increased in RDR6i plants infected by AbMV but decreased in those infected by TYLCSV compared to wild-type plants. In situ hybridization revealed a 6.5-fold increase in the number of AbMV-infected nuclei in RDR6i plants but without egress from the phloem tissues. These results support the concept that begomoviruses adopt different strategies to counteract plant defences and that TYLCSV evades the functions exerted by RDR6 in this host.

Background: Tomato yellow leaf curl virus (TYLCV) is a major monopartite virus in the family Geminiviridae and has caused severe yield losses in tomato and tobacco planting areas worldwide. Wall-associated kinases (WAKs) and WAK-like kinases (WAKLs) are a subfamily of the receptor-like kinase family implicated in cell wall signaling and transmitting extracellular signals to the cytoplasm, thereby regulating plant growth and development and resistance to abiotic and biotic stresses. Recently, many studies on WAK/WAKL family genes have been performed in various plants under different stresses; however, identification and functional survey of the WAK/WAKL gene family of Nicotiana benthamiana have not yet been performed, even though its genome has been sequenced for several years. Therefore, in this study, we aimed to identify the WAK/WAKL gene family in N. benthamiana and explore their possible functions in response to TYLCV infection., Results: Thirty-eight putative WAK/WAKL genes were identified and named according to their locations in N. benthamiana. Phylogenetic analysis showed that NbWAK/WAKLs are clustered into five groups. The protein motifs and gene structure compositions of NbWAK/WAKLs appear to be highly conserved among the phylogenetic groups. Numerous cis-acting elements involved in phytohormone and/or stress responses were detected in the promoter regions of NbWAK/WAKLs. Moreover, gene expression analysis revealed that most of the NbWAK/WAKLs are expressed in at least one of the examined tissues, suggesting their possible roles in regulating the growth and development of plants. Virus-induced gene silencing and quantitative PCR analyses demonstrated that NbWAK/WAKLs are implicated in regulating the response of N. benthamiana to TYLCV, ten of which were dramatically upregulated in locally or systemically infected leaves of N. benthamiana following TYLCV infection., Conclusions: Our study lays an essential base for the further exploration of the potential functions of NbWAK/WAKLs in plant growth and development and response to viral infections in N. benthamiana., (© 2023. The Author(s).)

Begomoviruses are members of the family Geminiviridae , a large and diverse group of plant viruses characterized by a small circular single-stranded DNA genome encapsidated in twinned quasi-icosahedral virions. Cultivated tomato ( Solanum lycopersicum L.) is particularly susceptible and is infected by >100 bipartite and monopartite begomoviruses worldwide. In Brazil, 25 tomato-infecting begomoviruses have been described, most of which are bipartite. Tomato mottle leaf curl virus (ToMoLCV) is one of the most important of these and was first described in the late 1990s but has not been fully characterized. Here, we show that ToMoLCV is a monopartite begomovirus with a genomic DNA similar in size and genome organization to those of DNA-A components of New World (NW) begomoviruses. Tomato plants agroinoculated with the cloned ToMoLCV genomic DNA developed typical tomato mottle leaf curl disease symptoms, thereby fulfilling Koch's postulates and confirming the monopartite nature of the ToMoLCV genome. We further show that ToMoLCV is transmitted by whiteflies, but not mechanically. Phylogenetic analyses placed ToMoLCV in a distinct and strongly supported clade with other begomoviruses from northeastern Brazil, designated the ToMoLCV lineage. Genetic analyses of the complete sequences of 87 ToMoLCV isolates revealed substantial genetic diversity, including five strain groups and seven subpopulations, consistent with a long evolutionary history. Phylogeographic models generated with partial or complete sequences predicted that the ToMoLCV emerged in northeastern Brazil >700 years ago, diversifying locally and then spreading widely in the country. Thus, ToMoLCV emerged well before the introduction of MEAM1 whiteflies, suggesting that the evolution of NW monopartite begomoviruses was facilitated by local whitefly populations and the highly susceptible tomato host. IMPORTANCE Worldwide, diseases of tomato caused by whitefly-transmitted geminiviruses (begomoviruses) cause substantial economic losses and a reliance on insecticides for management. Here, we describe the molecular and biological properties of tomato mottle leaf curl virus (ToMoLCV) from Brazil and establish that it is a NW monopartite begomovirus indigenous to northeastern Brazil. This answered a long-standing question regarding the genome of this virus, and it is part of an emerging group of these viruses in Latin America. This appears to be driven by widespread planting of the highly susceptible tomato and by local and exotic whiteflies. Our extensive phylogenetic studies placed ToMoLCV in a distinct strongly supported clade with other begomoviruses from northeastern Brazil and revealed new insights into the origin of Brazilian begomoviruses. The novel phylogeographic analysis indicated that ToMoLCV has had a long evolutionary history, emerging in northeastern Brazil >700 years ago. Finally, the tools used here (agroinoculation system and ToMoLCV-specific PCR test) and information on the biology of the virus (host range and whitefly transmission) will be useful in developing and implementing integrated pest management (IPM) programs targeting ToMoLCV.

Tomato yellow leaf curl virus (TYLCV), a monopartite begomovirus in the family Geminiviridae, is efficiently transmitted by the whitefly, Bemisia tabaci, and causes serious economic losses to tomato crops around the world. TYLCV-infected tomato plants develop distinctive symptoms of yellowing and leaf upward cupping. In recent years, excellent progress has been made in the characterization of TYLCV C4 protein function as a pathogenicity determinant in experimental plants, including Nicotiana benthamiana and Arabidopsis thaliana. However, the molecular mechanism leading to disease symptom development in the natural host plant, tomato, has yet to be characterized. The aim of the current study was to generate transgenic tomato plants expressing the TYLCV C4 gene and evaluate differential gene expression through comparative transcriptome analysis between the transgenic C4 plants and the transgenic green fluorescent protein (Gfp) gene control plants. Transgenic tomato plants expressing TYLCV C4 developed phenotypes, including leaf upward cupping and yellowing, that are similar to the disease symptoms expressed on tomato plants infected with TYLCV. In a total of 241 differentially expressed genes identified in the transcriptome analysis, a series of plant development-related genes, including transcription factors, glutaredoxins, protein kinases, R-genes and microRNA target genes, were significantly altered. These results provide further evidence to support the important function of the C4 protein in begomovirus pathogenicity. These transgenic tomato plants could serve as basic genetic materials for further characterization of plant receptors that are interacting with the TYLCV C4., Competing Interests: The authors have declared that no competing interests exist.

Tomato yellow leaf curl virus (TYLCV), a plant DNA virus of the genus Begomovirus, is transmitted by whiteflies of the Bemisia tabaci species complex in a persistent manner. Our previous study indicated that activation of the apoptosis pathway in whiteflies could facilitate TYLCV accumulation and transmission. Considering that temperature change can influence the spread of insect-borne plant viruses, we focused on plant virus induced-apoptosis to investigate the underlying mechanism of temperature regulation on plant virus transmission via an insect vector. We found that heat stress (40°C) on whiteflies could facilitate TYLCV accumulation and increase transmission to tomato plants. Despite upregulation of caspase-1 and caspase-3 gene expression, heat stress failed to induce an increase in the activation of cleaved caspase-3 and DNA fragmentation in TYLCV-infected whiteflies. However, our data failed to determine the role of heat stress in apoptosis modulation of insect-plant virus interplay while still providing clues to understand insect vectors and their transmitted plant viruses., (© 2021 Wiley Periodicals LLC.)

With climate warming, drought becomes a vital challenge for agriculture. Extended drought periods affect plant-pathogen interactions. We demonstrate an interplay in tomato between drought and infection with tomato yellow leaf curl virus (TYLCV). Infected plants became more tolerant to drought, showing plant readiness to water scarcity by reducing metabolic activity in leaves and increasing it in roots. Reallocation of osmolytes, such as carbohydrates and amino acids, from shoots to roots suggested a role of roots in protecting infected tomatoes against drought. To avoid an acute response possibly lethal for the host organism, TYLCV down-regulated the drought-induced activation of stress response proteins and metabolites. Simultaneously, TYLCV promoted the stabilization of osmoprotectants' patterns and water balance parameters, resulting in the development of buffering conditions in infected plants subjected to prolonged stress. Drought-dependent decline of TYLCV amounts was correlated with HSFA1-controlled activation of autophagy, mostly in the roots. The tomato response to combined drought and TYLCV infection points to a mutual interaction between the plant host and its viral pathogen., (© 2021 The Authors. Molecular Plant Pathology published by British Society for Plant Pathology and John Wiley & Sons Ltd.)

Chilli leaf curl virus (ChiLCV; genus: Begomovirus ), transmitted by Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) in a persistent-circulative manner, is a major constraint in chilli production. The present study demonstrates for the first time that a topical spray of naked double-stranded RNA (dsRNA) on chilli plants causes mortality and inability to acquire and transmit ChiLCV in B. tabaci . dsRNA targeting heat shock protein 70 ( hsp70 ) and fasciclin 2 ( fas2 ) of B. tabaci Asia II 1 was first assessed under controlled conditions through oral delivery. Hsp70 and fas2 dsRNA resulted in up to 82.22% and 72% mortality of B. tabaci and around 12.4- and 8.5-fold decreases in mRNA levels, respectively, 24 h post-ingestion. ChiLCV copies in hsp70 dsRNA-fed B. tabaci steadily decreased with an increase in dsRNA concentration and were undetectable at a higher concentration of dsRNA. However, ChiLCV copies significantly increased in fas2 dsRNA-fed B. tabaci . Transmission of ChiLCV by B. tabaci was completely inhibited post-24 h feeding on hsp70 dsRNA at 3 μg/mL. Naked hsp70 dsRNA was topically sprayed on ChiLCV-infected chilli plants like an insecticide. 67.77% mortality of B. tabaci , 4.6-fold downregulation of hsp70 mRNA, and 1.34 × 10 15 -fold decreased ChiLCV copies in B. tabaci were recorded when adults were exposed to the dsRNA-treated plants under semi-field conditions. Foliar application of naked dsRNA reduced the ChiLCV transmission by 75% without any visible symptoms in the inoculated plants. A total of 2 consecutive sprays of dsRNA provided significant protection to B. tabaci for up to 20 days under semi-field conditions.

Disease caused by Pepper yellow leaf curl virus (PepYLCV) is one of the greatest threats to pepper (Capsicum spp.) cultivation in the tropics and subtropics. Resistance to PepYLCV was previously identified in a few Capsicum accessions, but no resistance QTLs have been mapped. This study aimed to elucidate the genetics of PepYLCV resistance in C. annuum L. Augmented inoculation by the viruliferous whitefly Bemisia tabaci was used to evaluate parental lines and an F2 segregating population derived from a cross between resistant C. annuum line LP97 and susceptible C. annuum line ECW30R. Final evaluation was performed six weeks after inoculation using a standardized 5-point scale (0 = no symptoms to 4 = very severe symptoms). A high-density linkage map was constructed using genotyping-by-sequencing (GBS) to identify single-nucleotide polymorphism (SNP) markers associated with PepYLCV resistance in the F2 population. QTL analysis revealed three QTLs, peplcv-1, peplcv-7, and peplcv-12, on chromosomes P1, P7, and P12, respectively. Candidate genes associated with PepYLCV resistance in the QTL regions were inferred. In addition, single markers Chr7-LCV-7 and Chr12-LCV-12 derived from the QTLs were developed and validated in another F2 population and in commercial varieties. This work thus provides not only information for mapping PepYLCV resistance loci in pepper but also forms the basis for future molecular analysis of genes involved in PepYLCV resistance., Competing Interests: The authors declare that they have no competing interests. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Key Message: The role of miRNAs during viral pathogenesis is poorly understood in plants. Here, we demonstrate a miRNA/target module that acts as a susceptibility factor during ToLCNDV infection. Tomato leaf curl New Delhi virus (ToLCNDV) is a devastating pathogen that causes huge crop loss. It is spreading to new geographical locations at a very rapid rate-raising serious concerns. Evolution of insecticidal resistance in Bemisia tabaci which acts as the carrier for ToLCNDV has made insect control very difficult in the recent years. Thus, it is important that the host molecular mechanisms associated with ToLCNDV resistance/susceptibility are investigated to develop management strategies. In our study, we have identified that sly-miR166/SlyHB module acts as a susceptibility factor to ToLCNDV in Solanum lycopersicum. Sly-miR166 is differentially regulated upon ToLCNDV infection in two contrasting tomato cultivars; H-88-78-1 (tolerant to ToLCNDV) and Punjab Chhuhara (susceptible to ToLCNDV). Expression analysis of predicted sly-miR166 targets revealed that the expression of SlyHB is negatively correlated with its corresponding miRNA. Virus-induced gene silencing of SlyHB in the susceptible tomato cultivar resulted in the decrease in disease severity suggesting that SlyHB is a negative regulator of plant defence. In summary, our study highlights a miRNA/target module that acts as a susceptibility factor during ToLCNDV infection. To the best of our knowledge, this is the first report that highlights the role of sly-miR166/SlyHB module in ToLCNDV pathogenesis., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Whitefly, Bemisia tabaci (Gennadius) is an important pest of cotton causing direct damage as sap feeder and vector of Cotton leaf curl virus (CLCuV). Previous few studies suggest that female whiteflies are more efficient vector of begomovirusthan males, however the sex-biased transmission efficiency is still not clearly understood. Present studies with B. tabaci AsiaII-1 haplotype showed higher virus transmission efficiency of females compared to males. This variable begomovirus transmission efficiency has been related to previously identifiedkey factors associated with B. tabaci. The higher density of endosymbiont Arsenophonus and variable expression of some midgut proteins genes i.e. Cyclophilin, Knottin, Hsp40, Hsp70 may be possibly imparting higher vector competency to the females compared to males. The present studies suggest low abundance of Arsenophonus spp. as well as lower expressionof Cyclophilin genein males as compared to females. This is further supplemented by overexpression of Knottin, Hsp40, and Hsp70 genes in males compared to females and thus collectively all these factors might be playing a key role in low virus transmission efficiency of males. The relative density of Arsenophonus spp. and expression of midgut proteins genes in male and female whitefly first time enriches our understanding about sex-biased transmission efficiency of begomovirus., Competing Interests: The authors have declared that no competing interests exist.

A growing body of research points to a positive interplay between viruses and plants. Tomato yellow curl virus (TYLCV) is able to protect tomato host plants against extreme drought. To envisage the use of virus protective capacity in agriculture, TYLCV-resistant tomato lines have to be infected first with the virus before planting. Such virus-resistant tomato plants contain virus amounts that do not cause disease symptoms, growth inhibition, or yield loss, but are sufficient to modify the metabolism of the plant, resulting in improved tolerance to drought. This phenomenon is based on the TYLCV-dependent stabilization of amounts of key osmoprotectants induced by drought (soluble sugars, amino acids, and proteins). Although in infected TYLCV-susceptible tomatoes, stress markers also show an enhanced stability, in infected TYLCV-resistant plants, water balance and osmolyte homeostasis reach particularly high levels. These tomato plants survive long periods of time during water withholding. However, after recovery to normal irrigation, they produce fruits which are not exposed to drought, similarly to the control plants. Using these features, it might be possible to cultivate TYLCV-resistant plants during seasons characterized by water scarcity.

Because of limited free diffusion in the cytoplasm, viruses must use active transport mechanisms to move intracellularly. Nevertheless, how the plant single-stranded DNA begomoviruses hijack the host intracytoplasmic transport machinery to move from the nucleus to the plasmodesmata remains enigmatic. Here, we identified nuclear shuttle protein (NSP)-interacting proteins from Arabidopsis (Arabidopsis thaliana) by probing a protein microarray and demonstrated that the cabbage leaf curl virus NSP, a facilitator of the nucleocytoplasmic trafficking of viral (v)DNA, interacts in planta with an endosomal vesicle-localized, plant-specific syntaxin-6 protein, designated NSP-interacting syntaxin domain-containing protein (NISP). NISP displays a proviral function, unlike the syntaxin-6 paralog AT2G18860 that failed to interact with NSP. Consistent with these findings, nisp-1 mutant plants were less susceptible to begomovirus infection, a phenotype reversed by NISP complementation. NISP-overexpressing lines accumulated higher levels of vDNA than wild-type. Furthermore, NISP interacted with an NSP-interacting GTPase (NIG) involved in NSP-vDNA nucleocytoplasmic translocation. The NISP-NIG interaction was enhanced by NSP. We also showed that endosomal NISP associates with vDNA. NISP may function as a docking site for recruiting NIG and NSP into endosomes, providing a mechanism for the intracytoplasmic translocation of the NSP-vDNA complex toward and from the cell periphery., (© American Society of Plant Biologists 2021. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Key Message: A begomovirus resistance gene pepy-1, which encodes the messenger RNA surveillance factor Pelota, was identified in pepper (C. annuum) through map-based cloning and functional characterization. Pepper yellow leaf curl disease caused by begomoviruses seriously affects pepper (Capsicum spp.) production in a number of regions around the world. Ty genes of tomato, which confer resistance to the tomato yellow leaf curl virus, are the only begomovirus resistance genes cloned to date. In this study, we focused on the identification of begomovirus resistance genes in Capsicum annuum. BaPep-5 was identified as a novel source of resistance against pepper yellow leaf curl Indonesia virus (PepYLCIV) and pepper yellow leaf curl Aceh virus (PepYLCAV). A single recessive locus, which we named as pepper yellow leaf curl disease virus resistance 1 (pepy-1), responsible for PepYLCAV resistance in BaPep-5 was identified on chromosome 5 in an F 2 population derived from a cross between BaPep-5 and the begomovirus susceptible accession BaPep-4. In the target region spanning 34 kb, a single candidate gene, the messenger RNA surveillance factor Pelota, was identified. Whole-genome resequencing of BaPep-4 and BaPep-5 and comparison of their genomic DNA sequences revealed a single nucleotide polymorphism (A to G) located at the splice site of the 9th intron of CaPelota in BaPep-5, which caused the insertion of the 9th intron into the transcript, resulting in the addition of 28 amino acids to CaPelota protein without causing a frameshift. Virus-induced gene silencing of CaPelota in the begomovirus susceptible pepper No.218 resulted in the gain of resistance against PepYLCIV, a phenotype consistent with BaPep-5. The DNA marker developed in this study will greatly facilitate marker-assisted breeding of begomovirus resistance in peppers., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Several attempts have been made to identify antiviral genes against Tomato leaf curl New Delhi virus (ToLCNDV) and related viruses. This has led to the recognition of Ty genes ( Ty1-Ty6 ), which have been successful in developing virus-resistant crops to some extent. Owing to the regular appearance of resistance-breaking strains of these viruses, it is important to identify genes related to resistance. In the present study, we identified a ToLCNDV resistance ( R ) gene, SlSw5a , in a ToLCNDV-resistant tomato cultivar, H-88-78-1, which lacks the known Ty genes. The expression of SlSw5a is controlled by the transcription factor SlMyb33, which in turn is regulated by microRNA159 (sly-miR159). Virus-induced gene silencing of either SlSw5a or SlMyb33 severely increases the disease symptoms and viral titer in leaves of resistant cultivar. Moreover, in SlMyb33- silenced plants, the relative messenger RNA level of SlSw5a was reduced, suggesting SlSw5a is downstream of the sly-miR159-SlMyb33 module. We also demonstrate that SlSw5a interacts physically with ToLCNDV-AC4 (viral suppressor of RNA silencing) to trigger a hypersensitive response (HR) and generate reactive oxygen species at infection sites to limit the spread of the virus. The "RTSK" motif in the AC4 C terminus is important for the interaction, and its mutation completely abolishes the interaction with Sw5a and HR elicitation. Overall, our research reports an R gene against ToLCNDV and establishes a connection between the upstream miR159-Myb33 module and its downstream target Sw5a to activate HR in the tomato, resulting in geminivirus resistance., Competing Interests: The authors declare no competing interest.

Geminiviruses cause serious symptoms and devastating losses in crop plants. With a circular, single-stranded DNA genome, geminiviruses multiply their genomic DNA in the nucleus, requiring the nuclear shuttling of viral proteins and viral genomic DNAs. Many host factors, acting as proviral or antiviral factors, play key roles in geminivirus infections. Here, we report the roles of a tomato glutaredoxin (GRX), SlGRXC6, in the infection of Tomato yellow leaf curl virus (TYLCV), a single-component geminivirus. The V2 protein of TYLCV specifically and preferentially interacts with SlGRXC6 among the 55-member tomato GRX family that are broadly involved in oxidative stress responses, plant development, and pathogen responses. We show that overexpressed SlGRXC6 increases the nuclear accumulation of V2 by inhibiting its nuclear export and, in turn, inhibits trafficking of the V1 protein and viral genomic DNA. Conversely, the silenced expression of SlGRXC6 leads to an enhanced susceptibility to TYLCV. SlGRXC6 is also involved in symptom development as we observed a positive correlation where overexpression of SlGRXC6 promotes while knockdown of SlGRXC6 expression inhibits plant growth. We further showed that SlGRXC6 works with SlNTRC80, a tomato NADPH-dependent thioredoxin reductase, to regulate plant growth. V2 didn't interact with SlNTRC80 but competed with SlNTR80 for binding to SlGRXC6, suggesting that the V2-disrupted SlGRXC6-SlNTRC80 interaction is partially responsible for the virus-caused symptoms. These results suggest that SlGRXC6 functions as a host restriction factor that inhibits the nuclear trafficking of viral components and point out a new way to control TYLCV infection by targeting the V2-SlGRXC6 interaction., Competing Interests: The authors have declared that no competing interests exist.

Tomato ( Solanum lycopersicum ) is an important economic crop worldwide. However, tomato production is jeopardized by the devastating tomato yellow leaf curl disease caused by whitefly-transmitted begomoviruses (WTBs). In this study, we evaluated the efficacy of our previously developed plant antiviral immunity inducer, fungal F8-culture filtrate, on tomato to combat tomato yellow leaf curl Thailand virus (TYLCTHV), the predominant WTB in Taiwan. Our results indicated that F8-culture filtrate treatment induced strong resistance, did not reduce the growth of tomato, and induced prominent resistance against TYLCTHV both in the greenhouse and in the field. Among TYLCTHV-inoculated Yu-Nu tomato grown in the greenhouse, a greater percentage of plants treated with F8-culture filtrate (43-100%) were healthy-looking compared to the H 2 O control (0-14%). We found that TYLCTHV cannot move systemically only on the F8-culture filtrate pretreated healthy-looking plants. Tracking the expression of phytohormone-mediated immune maker genes revealed that F8-culture filtrate mainly induced salicylic acid-mediated plant immunity. Furthermore, callose depositions and the expression of the pathogen-induced callose synthase gene, POWDERY MILDEW RESISTANT 4 were only strongly induced by TYLCTHV on tomato pretreated with F8-culture filtrate. This study provides an effective way to induce tomato resistance against TYLCTHV.

By structuring farmers' informal networks of seed exchange, kinship systems play a key role in the dynamics of crop genetic diversity in smallholder farming systems. However, because many crop diseases are propagated through infected germplasm, local seed systems can also facilitate the dissemination of seedborne pathogens. Here, we investigate how the interplay of kinship systems and local networks of germplasm exchange influences the metapopulation dynamics of viruses responsible for the cassava mosaic disease (CMD), a major threat to food security in Africa. Combining anthropological, genetic and plant epidemiological data, we analyzed the genetic structure of local populations of the African cassava mosaic virus (ACMV), one of the main causal agents of CMD. Results reveal contrasted patterns of viral diversity in patrilineal and matrilineal communities, consistent with local modes of seed exchange. Our results demonstrate that plant virus ecosystems have also a cultural component and that social factors that shape regional seed exchange networks influence the genetic structure of plant virus populations., (© 2021. The Author(s).)