Search

Fruit ripening is a highly intricate process, where the dynamic interplay of soluble sugar and organic acid metabolism is crucial for developing the characteristic flavor qualities. Pyruvate orthophosphate dikinase (PPDK) plays a pivotal role in modulating the process of gluconeogenesis during plant development. However, the specific physiological role of PPDK in fruit development has yet to be elucidated. In this study, we investigated the expression pattern, subcellular localization and functional significance of SlPPDK in tomato fruits. Our results reveal that SlPPDK is highly expressed in fruits and flowers, with its expression progressively increasing as the fruit ripens. Subcellular localization analyses demonstrate that SlPPDK is distributed in the cell membrane, cytoplasm, and nucleus. Using CRISPR/Cas9 technology, we generated SlPPDK knockout mutants, which exhibited a marked reduction in enzyme activity, leading to significant alterations in sugar and organic acid metabolism. These findings highlight the critical role of SlPPDK in maintaining the sugar-acid balance essential for tomato flavor quality and provide a foundation for future breeding strategies aimed at enhancing tomato fruit flavor., 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 Elsevier Inc. All rights reserved.)

Autophagy is a mechanism for the degradation of cellular components in eukaryotes and plays a critical role in plant responses to abiotic stress. As a core member of the autophagy process, ATG8's role in how plants respond to heat stress remains unclear. To investigate the response of the tomato autophagy core member ATG8f to heat stress, we studied the key gene ATG8f and generated tomato lines overexpressing SlATG8f using the recombinant expression vector pBWA(V)HS. We observed that under heat stress, SlATG8f overexpression (OE) plants exhibited decreased heat tolerance compared to wild-type (WT) plants. Specifically, OE plants showed increased relative electrolyte leakage, reduced soluble solid content, elevated chlorophyll content, and higher autophagosome numbers, with less damage to chloroplasts and mitochondria. Additionally, expression of some ATG8 family genes and heat shock protein-related genes was upregulated. Moreover, SlATG8f overexpressing plants had higher pollen vitality and more intact pollen morphology. These results suggest that while SlATG8f overexpression renders plants more sensitive to heat, it helps mitigate high-temperature damage to tomato pollen by maintaining chloroplast integrity and interacting with heat shock proteins to respond to heat stress., (© 2024. The Author(s).)

Flower drop is a major cause for yield loss in many crops. Previously, we found that the tomato (Solanum lycopersicum) INFLORESCENCE DEFICIENT IN ABSCISSION-Like (SlIDL6) gene contributes to flower drop induced by low light. However, the molecular mechanisms by which SlIDL6 acts as a signal to regulate low light-induced abscission remain unclear. In this study, SlIDL6 was found to elevate cytosolic Ca2+ concentrations ([Ca2+]cyt) in the abscission zone (AZ), which was required for SlIDL6-induced flower drop under low light. We further identified that 1 calcium-dependent protein kinase gene, SlCPK10, was highly expressed in the AZ and upregulated by SlIDL6-triggered [Ca2+]cyt. Overexpression and knockout of SlCPK10 in tomato resulted in accelerated and delayed abscission, respectively. Genetic evidence further indicated that knockout of SlCPK10 significantly impaired the function of SlIDL6 in accelerating abscission. Furthermore, Ser-371 phosphorylation in SlCPK10 dependent on SlIDL6 was necessary and sufficient for its function in regulating flower drop, probably by stabilizing the SlCPK10 proteins. Taken together, our findings reveal that SlCPK10, as a downstream component of the IDL6 signaling pathway, regulates flower drop in tomato under low-light stress., Competing Interests: Conflict of interest statement: The authors declare no conflict of interest., (© The Author(s) 2024. Published by Oxford University Press on behalf of American Society of Plant Biologists. 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.)

Saline-alkali stress is a widely distributed abiotic stress that severely limits plant growth. γ-Aminobutyric acid (GABA) accumulates rapidly in plants under saline-alkali stress, but the underlying molecular mechanisms and associated regulatory networks remain unclear. Here, we report a MYB-like protein, I-box binding factor (SlMYBI), which positively regulates saline-alkali tolerance through induced GABA accumulation by directly modulating the glutamate decarboxylase (GAD) gene SlGAD1 in tomato (Solanum lycopersicum L.). Overexpression of SlGAD1 increased GABA levels and decreased reactive oxygen species accumulation under saline-alkali stress, while silencing of SlGAD1 further suggested that SlGAD1 plays an active role in GABA synthesis and saline-alkali tolerance of tomato. In addition, we found that SlMYBI activates SlGAD1 transcription. Both overexpression of SlMYBI and editing of SlMYBI using CRISPR-Cas9 showed that SlMYBI regulates GABA synthesis by modulating SlGAD1 expression. Furthermore, the interaction of SlNF-YC1 with SlMYBI enhanced the transcriptional activity of SlMYBI on SlGAD1 to further improve saline-alkali tolerance in tomato. Interestingly, we found that ethylene signaling was involved in the GABA response to saline-alkali stress by RNA-seq analysis of SlGAD1-overexpressing lines. This study elucidates the involvement of SlMYBI in GABA synthesis regulation. Specifically, the SlMYBI-SlNF-YC1 module is involved in GABA accumulation in response to saline-alkali stress., Competing Interests: Conflict of interest statement: The authors declare no conflict of interest., (© The Author(s) 2024. Published by Oxford University Press on behalf of American Society of Plant Biologists. 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.)

In tomato, sugar content is highly correlated with consumer preferences, with most consumers preferring sweeter fruit 1-4 . However, the sugar content of commercial varieties is generally low, as it is inversely correlated with fruit size, and growers prioritize yield over flavour quality 5-7 . Here we identified two genes, tomato (Solanum lycopersicum) calcium-dependent protein kinase 27 (SlCDPK27; also known as SlCPK27) and its paralogue SlCDPK26, that control fruit sugar content. They act as sugar brakes by phosphorylating a sucrose synthase, which promotes degradation of the sucrose synthase. Gene-edited SlCDPK27 and SlCDPK26 knockouts increased glucose and fructose contents by up to 30%, enhancing perceived sweetness without fruit weight or yield penalty. Although there are fewer, lighter seeds in the mutants, they exhibit normal germination. Together, these findings provide insight into the regulatory mechanisms controlling fruit sugar accumulation in tomato and offer opportunities to increase sugar content in large-fruited cultivars without sacrificing size and yield., Competing Interests: Competing interests: A patent on the use of SlCDPK27 and SlCDPK26 to improve fruit sugar content has been filed by S.H., J.Z., H.L., J.C. and G.Z. (CN202211616622.8; PCT/CN2023/138699). The other authors declare no competing interests., (© 2024. The Author(s).)

K + accumulation in plant tissues is a crucial factor for plant growth and development. The tomato high-affinity K + transporter SlHAK5 is essential for root K + acquisition from low external concentrations. It is also involved in K + accumulation in pollen and plant fertility as slhak5 KO plants show a low rate of pollen germination, impaired pollen tube growth and parthenocarpic fruits. Here, we present a thorough analysis of slhak5 flowers, which showed relevant defects at the anatomic, ionomic, metabolomic and transcriptomic levels. First, slhak5 flowers exhibited shorter styles and enlarged ovaries that, together with a low number of seeds in fruits from slhak5 X WT crosses, indicated an effect of the slhak5 mutation on female fertility. Second, a lower accumulation of Ca 2+ , as well as of several metabolites such as amino acids, citric acid and sugars, was observed in mutant flowers, whereas indole-3-acetic acid content was increased when compared to the wild-type. Third, RNAseq conducted on pistils and stamens of wild-type and slhak5 plants revealed that transport and signalling pathways are significantly enriched in the gene expression analyses of stamens. Thus, it can be concluded that a functional SlHAK5 transporter is required to maintain appropriate Ca 2+ , metabolite and gene expression levels in flowers, and its absence leads to important reductions in both male and female fertility., (© 2024 The Author(s). Physiologia Plantarum published by John Wiley & Sons Ltd on behalf of Scandinavian Plant Physiology Society.)

The development of viable pollen is a determinant of male fertility and plays an essential role in the reproductive process of angiosperms. Mitogen-activated protein kinase (MAPK) cascades modulate diverse aspects of plant growth, but their involvement in post-meiotic pollen development is unclear. In this study, SlMKK4 was identified as a crucial regulator in overseeing pollen development in tomatoes (Solanum lycopersicum). Utilizing CRISPR-associated protein 9 to disrupt SlMKK4 resulted in an obvious decrease in pollen viability. The results of cell biology and transcriptomic analyses demonstrated that SlMKK4 specifically regulates auxin and sugar metabolism as well as signal transduction during post-meiotic pollen development. This is supported by the finding that protein-protein interaction assays and in vitro phosphorylation assays indicate that SlMKK4 serves as the upstream MAPKK for SlMPK20, which exhibits a distinct function in regulating the uninucleate (UN) to binucleate (BN) transition during microgametogenesis in tomatoes. Moreover, pollen from transgenic plants experienced significant arrest predominantly at the BN stage, accompanied by subcellular abnormalities manifesting during the late UN microspore phase. Furthermore, transcriptomic analyses indicated that SlMKK4 knockout remarkably downregulated the expression of numerous genes regulating auxin and sugar metabolism as well as signal transduction in anthers. Therefore, our findings suggest that SlMKK4 may serve as one of the upstream SlMAPKKs of SlMPK20 and also play a pivotal role in modulating post-meiotic pollen development in tomato plants., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2024 Elsevier Masson SAS. All rights reserved.)

Environmental stress significantly affects plant growth and productivity. The effects of drought stress on plants are reflected primarily in enzyme activity, membrane systems, and cell-water loss. Here, the Kelch repeat F-box (KFB) protein family in tomato was systematically identified and analysed. Using bioinformatics, we identified 37 SlKFB family members in the tomato genome and analysed their protein structure, phylogenetic relationships, chromosome distribution, and expression under drought or biotic-stress conditions. Transcriptome data revealed that SlKFB members exhibit differential responses to drought stress, with significant differences in SlKFB16 and SlKFB34 expression. Functional analysis revealed that SlKFB16 functions in the cytoplasm and SlKFB34 in the nucleus and cytoplasm. Under drought stress, SlKFB16 and SlKFB34-silencing significantly reduced reactive oxygen species scavenging and resistance to drought stress. These findings provide a reference for further studies of the mechanisms of SlKFB16 and SlKFB34 in drought stress in tomato as well as a foundation for enhancing their resistance to drought stress., 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 Elsevier Masson SAS. All rights reserved.)

The use of compost tea is important to improve food safety. However, the effect of compost tea on N uptake and partitioning in tomato is unclear. In this study, we measured temporal and spatial changes in nitrogen content, enzyme activities, and expression levels of nitrogen transporters genes in different organs of tomato treated with five nutrient solutions. The results showed that the expression levels of ammonium transporter protein genes (AMT1s) increased and that of a nitrogen transporters gene (NRT2.1) decreased under treatment with compost tea, which promoted NH 4 + transport to the fruit and reduced nutrient wastage compared with the response to chemical fertilizers. In addition, the lowermost leaves on the stem showed reduced nitrate content, faster metabolism, and decreased chlorophyll a content, but fruit yield was not increased, in compost tea-treated plants. These changes were dependent on the expression level of the glutamine synthetase gene (GS1.1), which was increased in leaves and decreased in fruit. Compost tea influenced the expression of critical genes in the fruits and leaves, and improved the competitiveness of sexual reproductive growth as a sink for nitrogen. However, the benefits of compost tea were reduced when it was mixed chemical fertilizers. This research establishes a theoretical framework for optimization of organic vegetable cultivation and promoting the widespread production of organic crops., 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 Elsevier Masson SAS. All rights reserved.)

The cuticle is the first physical barrier covering the surface of tomatoes and plays an important role in multiple stress responses. But the molecular regulatory networks of cuticle formation are not fully understood. In this study, we found that SlMYB72 can interact with SlTAGL1 to regulate the formation of fruit cuticle in tomato. Downregulating the expression of SlMYB72 inhibits the formation of fruit cuticle, resulting in a reduced fruit cuticle thickness, accelerated postharvest water loss, and increased susceptibility to Botrytis cinerea. RNA sequencing analysis showed that downregulation of the SlMYB72 gene decreased the expression levels of genes related to fatty acid and cuticle metabolism. SlMYB72 regulates the cuticle formation by directly binding to the promoter of long-chain acyl-coA synthetases (SlLACS1) and medium-chain alkane hydroxylase (SlMAH1). Moreover, SlMYB72 interacts with SlTAGL1, which can enhance the transcriptional activation of SlMYB72 on the SlMAH1 promoter. Overall, our study expands our understanding of the regulation of cuticle formation by SlMYB72 and provides new insights into fruit shelf life extension via manipulation of cuticle content., (© 2024 Society for Experimental Biology and John Wiley & Sons Ltd.)

Chromoplasts are specialized plastids in plants involved in carotenoid synthesis, accumulation, and stress resistance. In tomatoes (Solanum lycopersicum), the Chromoplast-associated carotenoid binding protein (CHRC) regulates chromoplast development and carotenoid accumulation, although its precise mechanisms are not yet fully understood. To investigate the role of SlCHRC in carotenoid biosynthesis, we generated transgenic tomatoes using overexpression (oe-SlCHRC) and CRISPR/Cas9-mediated gene editing (cr-SlCHRC) techniques. The results demonstrated inhibited fruit ripening and delayed onset of color break in both transgenic lines. The oe-SlCHRC lines exhibited increased carotenoid accumulation, particularly (E/Z)-phytoene, lycopene, and γ-carotene, with abundant plastoglobules and carotenoid crystals observed via TEM. In contrast, cr-SlCHRC mutants showed a greener phenotype, reduced carotenoid content, and fewer plastoglobules at the BK + 10 stage. Transcriptome analysis indicated that SlCHRC influences key genes in carotenoid biosynthesis, such as SlNCED2, as well as genes related to chloroplast development, photosynthesis, and plastoglobule formation. Additionally, SlCHRC enhances heat stress tolerance in tomato fruits by upregulating heat shock proteins (HSPs), antioxidants, and proline accumulation. These findings indicate that SlCHRC plays a crucial role in improving tomato fruit quality under heat stress conditions., 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 Elsevier B.V. All rights reserved.)

Cold stress restricts the metabolic and physiological activities of plants, thereby affecting their growth and development. Although broad-complex, tramtrack, and bric-à-brac (BTB) proteins are essential for diverse biological processes and stress responses, the mechanisms underlying BTB-mediated cold responses remain not fully understood. Here, we characterize the function of the cold-induced SlBTB19 protein in tomato (Solanum lycopersicum). Overexpression of SlBTB19 resulted in increased plant sensitivity to cold stress, whereas SlBTB19 knockout mutants exhibited a cold-tolerance phenotype. Further analyses, including protein-protein interaction studies and cell-free degradation assays, revealed that SlBTB19 interacts with and destabilizes the transcription factor SlWRKY2. Using virus-induced gene silencing (VIGS) to silence SlWRKY2 in both wild-type and slbtb19 mutants, we provided genetic evidence that SlWRKY2 acts downstream of SlBTB19 in regulating cold tolerance. Importantly, we demonstrated that SlWRKY2 positively regulates cold tolerance in a CRT/DRE binding factor (CBF)-dependent manner. Under cold stress, SlWRKY2 binds to the W-box in the CBF1 and CBF3 promoters, directly activating their expression. In summary, our findings identify a SlBTB19-SlWRKY2 module that negatively regulates the CBF-dependent cold tolerance pathway in tomato., (© 2024 Society for Experimental Biology and John Wiley & Sons Ltd.)

Low temperatures can seriously affect apple yield and can also cause chilling injury to apple fruit. γ-aminobutyric acid (GABA) plays an important role in improving plant stress resistance. Some studies have reported that GABA can improve cold resistance in plants, only through exogenous treatment; however, the molecular mechanism of its resistance to low temperature is still unknown. This result suggested that exogenous GABA treatment of both apple seedlings and fruit could improve the resistance of apple to low temperatures. MdGAD1, a key gene involved in GABA synthesis, was overexpressed in tomato plants and apple callus to improve their cold tolerance. Both yeast one-hybrid and luciferase assay showed that MdCBF3 could bind to the MdGAD1 promoter to activate its expression and promote GABA synthesis. These results revealed a molecular mechanism utilizing the MdCBF3-MdGAD1 regulatory module that can enhance cold resistance by increasing endogenous GABA synthesis in apple., 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 B.V.)

Global warming poses a threat for crops, therefore, the identification of thermotolerance mechanisms is a priority. In plants, the core factors that regulate transcription under heat stress (HS) are well described and include several HS transcription factors (HSFs). Despite the relevance of alternative splicing in HS response and thermotolerance, the core regulators of HS-sensitive alternative splicing have not been identified. In tomato, alternative splicing of HSFA2 is important for acclimation to HS. Here, we show that several members of the serine/arginine-rich family of splicing factors (SRSFs) suppress HSFA2 intron splicing. Individual-nucleotide resolution UV cross-linking and immunoprecipitation (iCLIP) combined with RNA-Seq revealed that RS2Z35 and RS2Z36, which make up a plant-specific clade of SR proteins, not only regulate HSFA2 but approximately 50% of RNAs that undergo HS-sensitive alternative splicing, with preferential binding to purine-rich RNA motifs. Single and double CRISPR rs2z mutant lines show a dysregulation of splicing and exhibit lower basal and acquired thermotolerance compared to wild type plants. Our results suggest that RS2Z35 and RS2Z36 have a central role in mitigation of the negative effects of HS on RNA splicing homeostasis, and their emergence might have contributed to the increased capacity of plants to acclimate to high temperatures., (© The Author(s) 2024. Published by Oxford University Press on behalf of Nucleic Acids Research.)

The MYB transcription factor family plays a crucial regulatory role in plant growth, development, biological progress, and stress responses. Here, we identified a R2R3-MYB transcription factor gene, SlMYB78-like , from tomato and characterized its function by gene silencing via RNA interference (RNAi). The results exhibited that the silencing of SlMYB78-like reduced the sensitivity of tomato seedlings to exogenous ABA. In addition, when exposed to drought and salt stresses, the RNAi lines grown in soil showed decreased tolerance, with lower ABA accumulation, relative water content, and chlorophyll content while displaying higher relative conductivity and malondialdehyde (MDA) content than the wild type. Moreover, the expression of genes related to chlorophyll biosynthesis, photosynthesis, and ABA biosynthesis/response were down-regulated in SlMYB78-like -silenced lines. Notably, the transcript level of SlCYP707-A2 , which encodes a protein involved in ABA degradation, was up-regulated significantly after stresses. The transient expression assay Dual-luciferase (Dual-LUC) and a yeast one-hybrid (Y1H) assay demonstrated that SlMYB78-like bound to the promoter of SlCYP707-A2 . Additionally, the physical interaction between SlMYB78-like and SlDREB3, which functioned in ABA signaling transduction, was identified through yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays. Collectively, our study illustrates that SlMYB78-like participates in the abiotic stress response via the ABA pathway.

Plant height is a critical agronomic trait closely linked to yield, primarily regulated by Gibberellins (GA) and auxins, which interact in complex ways. However, the mechanism underlying their interactions remain incompletely understood. In this study, we identified a tomato mutant exhibiting significantly reduced plant height. Through gene cloning and bulked segregant analysis (BSA) sequencing, we found that the mutant gene corresponds to the tomato auxin response factor gene SlARF5/MP. Here, we show that overexpression of SlARF5/MP significantly enhances plant height. Additionally, treatment with GA 3 restored the plant height of the mutant to wild-type (WT) levels, indicating that GA content is a key factor influencing plant height. We also observed significant upregulation of GA-biosynthesis genes, including GA2-oxidases GA20ox3 and GA20ox4, as well as the GA 3 biosynthesis gene GA3ox1, in SlARF5-overexpressing plants. Furthermore, we demonstrated that SlARF5 directly binds to SlGA2ox3, which mediates the conversion of GA 3 to inactive GA, therebyregulating its expression. Our findings suggest that SlARF5 modulates GA 3 metabolism by regulating GA synthesis genes, ultimately leading to alterations in plant height., (© 2024. The Author(s).)

PsbS protein is essential for the rapid induction of non-photochemical quenching (NPQ) under low night temperatures (LNTs), but its stability is often affected by adverse environmental conditions. However, the regulatory mechanism for the stability of PsbS or chloroplast proteins remains to be fully characterized. We show that LNT decreases NPQ levels and SlPsbS protein abundance in tomato leaves. LNT-activated chloroplast vesicles (SlCVs) targeting the chloroplasts induce the formation of CV-containing vesicles (CCVs) containing SlPsbS, exported from the chloroplasts. Subsequently, SlCV and SlPsbS contact COP9 signalosome subunit 5A (SlCSN5A) in the cytosol and are ubiquitinated and degraded. Genetic evidence demonstrates that the overexpression of SlCV aggravates SlPsbS protein degradation, whereas silencing of SlCSN5 and SlCV delays LNT-induced NPQ reduction and SlPsbS protein turnover. This study reveals a ubiquitin-dependent degradation pathway of chloroplast proteins co-mediated by CV and CSN5A, thereby providing a basic reference for the regulation of chloroplast protein stability under stress conditions., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Transcription factors (TFs) are crucial for regulating fruit ripening in tomato (Solanum lycopersicum). The GRAS (GAI, RGA, and SCR) TFs are involved in various physiological processes, but their role in fruit ripening has seldom been reported. We have previously identified a gene encoding GRAS protein named SlFSR (Fruit Shelf-life Regulator), which is implicated in fruit ripening by regulating cell wall metabolism; however, the underlying mechanism remains unclear. Here, we demonstrate that SlFSR proteins are localized to the nucleus, where they could bind to specific DNA sequences. SlFSR acts downstream of the master ripening regulator RIN and could collaborate with RIN to control the ripening process by regulating expression of ethylene biosynthesis genes. In SlFSR-CR (CRISPR/Cas9) mutants, the initiation of fruit ripening was not affected but the reduced ethylene production and a delayed coloring process occurred. RNA-sequencing (RNA-seq) and promoter analysis reveal that SlFSR directly binds to the promoters of two key ethylene biosynthesis genes (SlACO1 and SlACO3) and activates their expression. However, SlFSR-CR fruits displayed a significant down-regulation of key rate-limiting genes (SlDXS1 and SlGGPPS2) in the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway, which may account for the impaired lycopene synthesis. Altogether, we propose that SlFSR positively regulates ethylene biosynthesis and lycopene accumulation, providing valuable insights into the molecular mechanisms underlying fruit ripening., Competing Interests: Declaration of competing interest All authors have read and approved this version of the article, and due care has been taken to ensure the integrity of this work. The authors declare that they have no conflict of interest., (Copyright © 2024. Published by Elsevier Masson SAS.)

Long non-coding RNAs (lncRNAs) play crucial roles in various biological processes in plants. However, the functional mechanism of lncRNAs in fruit ripening, particularly the transition from unripe to ripe stages, remains elusive. One such lncRNA1840, reported by our group, was found to have important role in tomato fruit ripening. In the present study, we gain insight into its functional role in fruit ripening. CRISPR-Cas9 mediated lncRNA1840 mutants caused the delayed tomato fruit ripening. Notably, loss function of lncRNA1840 did not directly impact ethylene signaling but rather delay ethylene synthesis. Transcriptomic analysis revealed differences in the expression of ripening related genes in lncRNA1840 mutants, suggesting that it is involved in gene regulation of fruit ripening. We used Chromatin Isolation by RNA Purification (ChIRP)-Seq to identify lncRNA1840 binding sites on chromatin. ChIRP-seq suggested that lncRNA1840 had occupancy on 40 genes, but none of them is differentially expressed genes in transcriptomic analysis, which indicated lncRNA1840 might indirectly modulate the gene expression. ChIRP-mass spectrometry analysis identified potential protein interactors of lncRNA1840, Pre-mRNA processing splicing factor 8, highlighting its involvement in post-transcriptional regulatory pathways. In summary, lncRNA1840 is key player in tomato plant growth and fruit ripening, with multifaceted roles in gene expression and regulatory networks., (© 2024 Society for Experimental Biology and John Wiley & Sons Ltd.)

Many studies showed NAC transcription factors play an important role in fruit ripening. Moreover, sucrose and starch metabolism is also closely related to fruit ripening. However, there are a few studies focus on whether NAC regulates sucrose and starch metabolism to influence fruit ripening. In this study, virus-induced gene silencing (VIGS) of SlNAP1 suppressed fruit ripening and delayed color transformation. The chlorophyll (including Chla, Chlb, and Chla + b) degradation and carotenoid synthesis in SlNAP1-silenced fruits were dramatically suppressed. Silencing SlNAP1 decreased soluble sugar and reducing sugar accumulation in fruits, and increased starch content. The activity of starch degrading enzymes, including α amylase (AMY) and β amylase (BAM) was significantly lower in SlNAP1-silenced fruits than in the control fruits, whereas denosine diphosphoglucose pyrophosphorylase (AGP) activity was significantly higher. In addition, the expression of starch degradation-related genes (SlAMY1, SlAMY2, SlBAM1, SlBAM7, SlGWD, SlPWD) in SlNAP1-silenced fruits was significantly suppressed, while starch synthesis-related genes (SlAGPase1, SlAGPase2) was significantly increased. Compared with the control fruits, SlNAP1-silenced fruits showed significantly lower sucrose and glucose content. The expression level of sucrose and glucose metabolism-related genes such as Slsus1, Slsus3, SlSPS, SlHxk1, SlHxk2, SlPK1, and SlPK2 was significantly lower in SlNAP1-silenced fruits than in the control fruits. Overall, this study revealed that SlNAP1 gene might positively regulate fruit ripening by influencing carbohydrate metabolism., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2024 Elsevier Masson SAS. All rights reserved.)

FW2.2 (standing for FRUIT WEIGHT 2.2), the founding member of the CELL NUMBER REGULATOR (CNR) gene family, was the first cloned gene underlying a quantitative trait locus (QTL) governing fruit size and weight in tomato (Solanum lycopersicum). However, despite this discovery over 20 yr ago, the molecular mechanisms by which FW2.2 negatively regulates cell division during fruit growth remain undeciphered. In the present study, we confirmed that FW2.2 is a membrane-anchored protein whose N- and C-terminal ends face the apoplast. We unexpectedly found that FW2.2 is located at plasmodesmata (PD). FW2.2 participates in the spatiotemporal regulation of callose deposition at PD and belongs to a protein complex which encompasses callose synthases. These results suggest that FW2.2 has a regulatory role in cell-to-cell communication by modulating PD transport capacity and trafficking of signaling molecules during fruit development., Competing Interests: Conflict of interest statement. None declared., (© The Author(s) 2024. Published by Oxford University Press on behalf of American Society of Plant Biologists.)

Tomato (Solanum lycopersicum L.) is rich in nutrients and has been an important target for enhancing the accumulation of various metabolites. Tomato also contains cholesterol-derived molecules, steroidal glycoalkaloids (SGAs), which contribute to pathogen defense but are toxic to humans and considered antinutritional compounds. Previous studies suggest the role of various transcription factors in SGA biosynthesis; however, the role of light and associated regulatory factors has not been studied in tomatoes. Here, we demonstrated that SGA biosynthesis is regulated by light through the ELONGATED HYPOCOTYL 5 homolog, SlHY5, by binding to light-responsive G-boxes present in the promoters of structural and regulatory genes. SlHY5 complemented Arabidopsis (Arabidopsis thaliana) and tobacco (Nicotiana tabacum) hy5 mutants at molecular, morphological, and biochemical levels. CRISPR/Cas9-based knockout tomato plants, SlHY5CR, showed downregulation of SGA and phenylpropanoid pathway genes, leading to a significant reduction in SGA (α-tomatine and dehydrotomatine) and flavonol contents, whereas plants overexpressing SlHY5 (SlHY5OX) showed the opposite effect. Enhanced SGA and flavonol levels in SlHY5OX lines provided tolerance against Alternaria solani fungus, while SlHY5CR lines were susceptible to the pathogen. This study advances our understanding of the HY5-dependent light-regulated biosynthesis of SGAs and flavonoids and their role in biotic stress in tomatoes., Competing Interests: Conflict of interest statement. None declared., (© The Author(s) 2024. Published by Oxford University Press on behalf of American Society of Plant Biologists. 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 circadian dynamics of the expression of key genes of carotenoid metabolism (PSY2, LCYE, CrtRB1, and NCED1) in the photosynthetic tissue of tomato Solanum lycopersicum L. (cultivar Korneevsky) plants was characterized. An in silico analysis of the gene expression pattern was carried out and a high level of their transcripts was detected in the leaf tissue. qRT-PCR analysis of gene expression was performed at six time points during the day and showed the highest levels of PSY2, LCYE, and NCED1 transcripts in the second half of the light phase and CrtRB1 at the end of the dark phase. The content and composition of carotenoids in leaf tissue in the middle of the day was determined; it was shown that the leaf accumulates 1.5 times more compounds of the ɛ/β-branch of carotenoid biosynthesis pathway than compounds of the β/β-branch., (© 2024. Pleiades Publishing, Ltd.)

Potassium (K + ) is an essential macronutrient which contributes to osmotic- and turgor-related processes in plants. Calcineurin-B like Interacting Protein Kinases (CIPKs) play crucial roles in plants under low-K + supply since they activate root K + uptake transport systems such as AKT1 and AtHAK5. In Arabidopsis, AtCIPK9 is important for low-K + tolerance since atcipk9 plants exhibited poor growth and leaf chlorosis when K + was scarce. Part of these phenotypes could be ascribed to the activation of AtHAK5 by AtCIPK9. It has been reported that important differences exist between Arabidopsis and other plant species such as tomato with respect to the regulation of K + uptake systems. Thus, our aim was to evaluate the contribution of SlCIPK9, the homologous protein of AtCIPK9 in tomato, to K + nutrition. Unexpectedly, phenotyping experiments carried out with slcipk9 loss-of-function mutants revealed that SlCIPK9 did not play a clear role in tomato K + homeostasis. By contrast, it was found that SlCIPK9 contributed to pollen tube elongation, but not to pollen germination, via a K + -independent mechanism. Therefore, our results highlight the remarkable differences that exist in Ca 2+ signaling pathways between plant species and encourage the realization of more comparative studies as the one presented here., 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 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1), a pivotal repressor in plant photomorphogenesis, has been extensively studied in various plant processes. However, the specific roles of COP1 in fruit remain poorly understood. Here, we functionally characterized SlCOP1-1 (also known as LeCOP1), an Arabidopsis (Arabidopsis thaliana) COP1 ortholog, in tomato (Solanum lycopersicum) fruit ripening and disease resistance. Despite the clear upregulation of SlCOP1-1 during fruit ripening, knockout or overexpression (OE) of SlCOP1-1 in tomatoes only minimally affected ripening. Intriguingly, these genetic manipulations substantially altered fruit resistance to the fungal pathogen Botrytis cinerea. Proteomic analysis revealed differential accumulation of proteins associated with fruit disease resistance upon SlCOP1-1 knockout or OE. To unravel the mechanism of SlCOP1-1 in disease resistance, we conducted a screen for SlCOP1-1-interacting proteins and identified the stress-related bZIP transcription factor SlOpaque2. We provide evidence that SlOpaque2 functions in tomato resistance to B. cinerea, and SlCOP1-1-mediated mono-ubiquitination and stabilization of SlOpaque2 contributes to fruit resistance against B. cinerea. Our findings uncover a regulatory role of COP1 in controlling fruit disease resistance, enriching our understanding of the regulatory network orchestrating fruit responses to disease., Competing Interests: Conflict of interest statement. The authors declare no conflict of interests., (© The Author(s) 2024. Published by Oxford University Press on behalf of American Society of Plant Biologists.)

Competing Interests: Conflict of interest statement. The authors do not declare any conflict of interest.

Systemin, the first peptide hormone identified in plants, was initially isolated from tomato (Solanum lycopersicum) leaves. Systemin mediates local and systemic wound-induced defense responses in plants, conferring resistance to necrotrophic fungi and herbivorous insects. Systemin is recognized by the leucine-rich-repeat receptor-like kinase (LRR-RLK) receptor SYSTEMIN RECEPTOR1 (SYR1), but how the systemin recognition signal is transduced to intracellular signaling pathways to trigger defense responses is poorly understood. Here, we demonstrate that SERK family LRR-RLKs function as co-receptors for SYR1 to mediate systemin signal transduction in tomato. By using chemical genetic approaches coupled with engineered receptors, we revealed that the association of the cytoplasmic kinase domains of SYR1 with SERKs leads to their mutual trans-phosphorylation and the activation of SYR1, which in turn induces a wide range of defense responses. Systemin stimulates the association between SYR1 and all tomato SERKs (SlSERK1, SlSERK3A, and SlSERK3B). The resulting SYR1-SlSERK heteromeric complexes trigger the phosphorylation of TOMATO PROTEIN KINASE 1B (TPK1b), a receptor-like cytoplasmic kinase that positively regulates systemin responses. Additionally, upon association with SYR1, SlSERKs are cleaved by the Pseudomonas syringae effector HopB1, further supporting the finding that SlSERKs are activated by systemin-bound SYR1. Finally, genetic analysis using Slserk mutants showed that SlSERKs are essential for systemin-mediated defense responses. Collectively, these findings demonstrate that the systemin-mediated association of SYR1 and SlSERKs activates defense responses against herbivorous insects., (© 2024 The Authors. Journal of Integrative Plant Biology published by John Wiley & Sons Australia, Ltd on behalf of Institute of Botany, Chinese Academy of Sciences.)

Loquat (Eriobotrya japonica Lindl.) is a popular fruit and medicinal plant. Proanthocyanidins (PAs), as one of the main types of flavonoids, are the key components of loquat fruit quality and medicinal properties. However, the identification of transcription factors (TFs) involved in PA accumulation in loquat remains limited. R2R3-MYB TFs play key regulatory role in PA accumulation in plants. In this study, 190 R2R3-MYB TFs were identified in loquat genome. Combined with transcriptome data, R2R3-MYB TF EjMYB5 involved in PA accumulation in loquat was isolated. EjMYB5 was transcriptional activator localized to nucleus. Expression of EjMYB5 was closely related to PA accumulation in loquat fruits. Heterogenous overexpression of EjMYB5 in tomato (Solanum lycopersicum) inhibited anthocyanin accumulation and promoted PA accumulation. Additionally, transient overexpression of EjMYB5 in tobacco (Nicotiana benthamiana) leaves promoted PA accumulation by upregulating flavonoid biosynthesis genes (NtDFR, NtANS, and NtLAR). Transcriptome analysis of EjMYB5-overexpressing tomato fruits suggested that EjMYB5 was involved in several biological pathways, including lipid metabolism, MAPK signaling, phenylpropanoid biosynthesis, and flavonoid biosynthesis. Collectively, our findings provided basic data for further analysis the function of R2R3-MYB TFs in loquat, and revealed that EjMYB5 functioned as PA accumulation in loquat., 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 Elsevier B.V. All rights reserved.)

Arbuscular mycorrhizal (AM) fungi improve plant growth, nutrition, fitness and stress tolerance while AM fungi obtain carbohydrates and lipids from the host. This whole process of mutual benefit requires substantial alterations in the structural and functional aspects of the host root cells. These modifications ultimately culminate in the formation of arbuscules, which are specialized intraradical and highly branched fungal structures. Arbuscule-containing cells undergo massive reprogramming to hosting arbuscule and members of the GRAS transcription factor family have been characterized as AM inducible genes which play a pivotal role in these process. Here, we show a functional analysis for the GRAS transcription factor SCL3/SlGRAS18 in tomato. SlGRAS18 interacts with SlDELLA, a central regulator of AM formation. Silencing of SlGRAS18 positively impacts arbuscule development and the improvement in symbiotic status, favouring flowering and therefore progress in the formation and development of fruits in SlGRAS18 silenced plants which parallel to a discernible pattern of mineral nutrient redistribution in leaves. Our results advance the knowledge of GRAS transcription factors involved in the formation and establishment of AM symbiosis and provide experimental evidence for how specific genetic alterations can lead to more effective AM symbiosis., 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 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

The plant-specific IDD transcription factors (TFs) are vital for regulating plant growth and developmental processes. However, the characteristics and biological roles of the IDD gene family in tomato ( Solanum lycopersicum ) are still largely unexplored. In this study, 17 SlIDD genes were identified in the tomato genome and classified into seven subgroups according to the evolutionary relationships of IDD proteins. Analysis of exon-intron structures and conserved motifs reflected the evolutionary conservation of SlIDDs in tomato. Collinearity analysis revealed that segmental duplication promoted the expansion of the SlIDD family. Ka/Ks analysis indicated that SlIDD gene orthologs experienced predominantly purifying selection throughout evolution. The analysis of cis -acting elements revealed that the promoters of SlIDD genes contain numerous elements associated with light, plant hormones, and abiotic stresses. The RNA-seq data and qRT-PCR experimental results showed that the SlIDD genes exhibited tissue-specific expression. Additionally, Group A members from Arabidopsis thaliana and rice are known to play a role in regulating plant shoot gravitropism. QRT-PCR analysis confirmed that the expression level of SlIDD15 in Group A was high in the hypocotyls and stems. Subcellular localization demonstrated that the SlIDD15 protein was localized in the nucleus. Surprisingly, the loss-of-function of SlIDD15 by CRISPR/Cas9 gene editing technology did not display obvious gravitropic response defects, implying the existence of functional redundant factors within SlIDD15 . Taken together, this study offers foundational insights into the tomato IDD gene family and serves as a valuable guide for exploring their molecular mechanisms in greater detail.

Enhancing drought tolerance in crops and understanding the underlying mechanisms have been subject of intense research. The precise function and molecular mechanisms of B-box zinc finger proteins (BBX) remain elusive. Here, we report a natural allele of BBX18 (BBX18 TT ) that encodes a C-terminal truncated protein. While most wild tomato germplasms contain the BBX18 CC allele and show more drought tolerant, modern cultivated tomatoes mostly carry BBX18 TT allele and are more drought sensitive. Knockout of BBX18 leads to improved drought tolerance in transgenic plants of cultivated tomato. Ascorbate peroxidase 1 (APX1) is identified as a BBX18-interacting protein that acts as a positive regulator of drought resistance in tomato. Chromatin immunoprecipitation sequencing analyses reveal that BBX18 binds to a unique cis-acting element of the APX1 promoter and represses its gene expression. This study provides insights into the molecular mechanism underlying drought resistance mediated by the BBX18-APX1 module in plants., (© 2024. The Author(s).)

ELONGATED HYPOCOTOYL5 (HY5) and PHYTOCHROME INTERACTING FACTORs (PIFs) are two types of important light-related regulators of plant growth, however, their interplay remains elusive. Here, we report that the activated tomato ( Solanum lycopersicum ) HY5 (SlHY5) triggers the transcription of a Calcium-dependent Protein Kinase SlCPK27 . SlCPK27 interacts with and phosphorylates SlPIF4 at Ser-252 and Ser-308 phosphosites to promote its degradation. SlPIF4 promotes hypocotyl elongation mainly by activating the transcription of SlDWF , a key gene in brassinosteroid (BR) biosynthesis. Such a SlHY5-SlCPK27-SlPIF4-BR cascade not only plays a crucial role in photomorphogenesis but also regulates thermomorphogenesis. Our results uncover a previously unidentified mechanism that integrates Ca 2+ signaling with the light signaling pathways to regulate plant growth by modulating BR biosynthesis in response to changes in ambient light and temperature., Competing Interests: Competing interests statement:The authors declare no competing interest.

Cysteine desulfhydrase catalyses the generation of the signaling molecule hydrogen sulfide (H2S) in plants. In this study, we found that H2S can inhibit tomato (Solanum lycopersicum) fruit ripening and SlWRKY6 undergoes differential protein persulfidation in SlLCD1-overexpressing leaves. Then, further study indicated that SlWRKY6 could be persulfidated by H2S at Cys396. By construction of slwrky6 mutants and SlWRKY6-OE lines, we found that SlWRKY6 positively regulates leaf senescence and fruit ripening by activating the transcription of ripening-related genes STAYGREEN 1 (SlSGR1) and Senescence-Associated Gene 12 (SlSAG12). In addition, SlWRKY6 interacted with kinase SlMAPK4 and was phosphorylated at Ser33. Dual-luciferase transient expression assays and electrophoretic mobility shift assays indicated that SlWRKY6 persulfidation attenuated its transcriptional regulation of target genes SlSGR1 and SlSAG12, whereas SlWRKY6 phosphorylation by SlMAPK4 activated the transcription of target genes to promote fruit ripening. Moreover, we provided evidence that SlWRKY6 persulfidation attenuated its SlMAPK4-mediated phosphorylation to inhibit tomato fruit ripening. By transient expression of SlWRKY6, SlWRKY6C396A, SlWRKY6S33A, and SlWRKY6S33D in slwrky6 fruits, we found that SlWRKY6 persulfidation attenuated the expression of SlSGR1 and SlSAG12 thereby delaying tomato fruit ripening, while SlWRKY6 phosphorylation increased the expression of target genes. As tomato fruits ripened, endogenous H2S production decreased, while SlMAPK4 expression increased. Therefore, our findings reveal a model in which SlWRKY6 persulfidation due to higher endogenous H2S levels in un-ripened fruit inhibits its ability to activate SlSGR1 and SlSAG12 expression, while SlWRKY6 phosphorylation by SlMAPK4 activates its transcriptional activity, thereby promoting tomato fruit ripening., Competing Interests: Conflict of interest statement. None declared., (© The Author(s) 2024. Published by Oxford University Press on behalf of American Society of Plant Biologists. 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.)

Competing Interests: Conflict of interest statement. None declared.

The economic impact of fruit cracking in pomegranate products is substantial. In this study, we present the inaugural comprehensive analysis of transcriptome and metabolome in the outermost pericarp of pomegranate fruit in bagging conditions. Our investigation revealed a notable upregulation of differentially expressed genes (DEGs) associated with the calcium signaling pathway (76.92%) and xyloglucan endotransglucosylase/hydrolase (XTH) genes (87.50%) in the fruit peel of non-cracking fruit under bagging. Metabolomic analysis revealed that multiple phenolics, flavonoids, and tannins were identified in pomegranate. Among these, calmodulin-like 23 (PgCML23) exhibited a significant correlation with triterpenoids and demonstrated a marked upregulation under bagging treatment. The transgenic tomatoes overexpressing PgCML23 exhibited significantly higher cellulose content and xyloglucan endotransglucosylase (XET) enzyme activity in the pericarp at the red ripening stage compared to the wild type. Conversely, water-soluble pectin content, polygalacturonase (PG), and β-galactosidase (β-GAL) enzyme activities were significantly lower in the transgenic tomatoes. Importantly, the heterologous expression of PgCML23 led to a substantial reduction in the fruit cracking rate in tomatoes. Our findings highlight the reduction of fruit cracking in bagging conditions through the manipulation of PgCML23 expression., 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 © 2023. Published by Elsevier Ltd.)

Type 2C protein phosphatases (PP2Cs) are emerging as important regulators of plant immune responses, although little is known about how they might impact nucleotide-binding, leucine-rich repeat (NLR)-triggered immunity (NTI). We discovered that expression of the PP2C immunity-associated candidate 14 gene (Pic14) is induced upon activation of the Pto/Prf-mediated NTI response in tomato. Pto/Prf recognizes the effector AvrPto translocated into plant cells by the pathogen Pseudomonas syringae pv. tomato (Pst) and activate a MAPK cascade and other responses which together confer resistance to bacterial speck disease. Pic14 encodes a PP2C with an N-terminal kinase-interacting motif (KIM) and a C-terminal phosphatase domain. Upon inoculation with Pst-AvrPto, Pto/Prf-expressing tomato plants with loss-of-function mutations in Pic14 developed less speck disease, specifically in older leaves, compared to wild-type plants. Transient expression of Pic14 in leaves of Nicotiana benthamiana and tomato inhibited cell death typically induced by Pto/Prf and the MAPK cascade members M3Kα and Mkk2. The cell death-suppressing activity of Pic14 was dependent on the KIM and the catalytic phosphatase domain. Pic14 inhibited M3Kα- and Mkk2-mediated activation of immunity-associated MAPKs and Pic14 was shown to be an active phosphatase that physically interacts with and dephosphorylates Mkk2 in a KIM-dependent manner. Together, our results reveal Pic14 as an important negative regulator of Pto/Prf-triggered immunity by interacting with and dephosphorylating Mkk2., (© 2024 Society for Experimental Biology and John Wiley & Sons Ltd.)

Plant intracellular nucleotide-binding and leucine-rich repeat immune receptors (NLRs) play a key role in activating a strong pathogen defense response. Plant NLR proteins are tightly regulated and accumulate at very low levels in the absence of pathogen effectors. However, little is known about how this low level of NLR proteins is able to induce robust immune responses upon recognition of pathogen effectors. Here, we report that, in the absence of effector, the inactive form of the tomato NLR Sw-5b is targeted for ubiquitination by the E3 ligase SBP1. Interaction of SBP1 with Sw-5b via only its N-terminal domain leads to slow turnover. In contrast, in its auto-active state, Sw-5b is rapidly turned over as SBP1 is upregulated and interacts with both its N-terminal and NB-LRR domains. During infection with the tomato spotted wilt virus, the viral effector NSm interacts with Sw-5b and disrupts the interaction of Sw-5b with SBP1, thereby stabilizing the active Sw-5b and allowing it to induce a robust immune response., (© 2024. The Author(s).)

High temperature (HT) severely restricts plant growth, development, and productivity. Plants have evolved a set of mechanisms to cope with HT, including the regulation of heat stress transcription factors (Hsfs) and heat shock proteins (Hsps). However, it is not clear how the transcriptional and translational levels of Hsfs and Hsps are controlled in tomato. Here, we reported that the HT-induced transcription factor SlWRKY55 recruited SlVQ11 to coordinately regulate defense against HT. SlWRKY55 directly bound to the promoter of SlHsfA2 and promoted its expression, which was increased by SlVQ11. Moreover, both SlWRKY55 and SlVQ11 physically interacted with SlHsfA2 to enhance the transcriptional activity of SlHsfA2. Thus, our results revealed a molecular mechanism that the SlWRKY55/SlVQ11-SlHsfA2 cascade enhanced thermotolerance and provided potential target genes for improving the adaptability of crops to HT., (© 2024 Society for Experimental Biology and John Wiley & Sons Ltd.)

A lower concentration of cadmium (Cd), a hazardous and non-essential element for plant growth, will have deleterious effects on plants and endanger human health. Histone demethylase (JHDM) is important for plants' ability to withstand abiotic stress, according to an increasing number of studies. The degree of expression of the SlJMJ18 and SlJMJ23 genes in different tomato tissues was confirmed by this study. These two genes were responsive to the heavy metals Cd, Hg, Pb, and Cu stress, according to fluorescence quantification and GUS staining. Interestingly, the overexpression transgenic Arabidopsis plants of two genes have different responses to Cd stress. While SlJMJ18-OE lines consistently display Cd resistance but an early-flowering phenotype, SlJMJ23-OE plants have sensitivity during the post-germination stage and then greater tolerance to Cd stress. It was discovered that these two genes may affect cadmium tolerance of plants by regulating the expression of hormone synthesis related genes and hormone contents (BRs and ABA). Moreover, SlJMJ23 may resist cadmium stress by increasing the total phenol content in plants. The functional significance of JMJs is better understood in this study, which also offers a theoretical foundation for the use of molecular technology to develop plants resistant to Cd and an experimental basis for the efficient use of land resources., 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 Elsevier B.V. All rights reserved.)

Seed germination is a critical phase for the life cycle and propagation of higher plants. This study explores the role of SlWRKY37, a WRKY transcription factor in tomato, in modulating seed germination. We discovered that SlWRKY37 expression is markedly downregulated during tomato seed germination. Through CRISPR/Cas9-mediated editing, we demonstrate that SlWRKY37 knockout enhances germination, while its overexpression results in a delay compared to the wild type. Transcriptome analysis revealed 679 up-regulated and 627 down-regulated genes in Slwrky37-CRISPR deletion mutants relative to the wild type. Gene ontology (GO) enrichment analysis indicated these differentially expressed genes are linked to seed dormancy, abscisic acid homeostasis, and protein phosphorylation pathways. Bioinformatics and biochemical assays identified SlABI5-like7 and SlLEA2 as key transcriptional targets of SlWRKY37, integral to tomato seed dormancy regulation. Additionally, SlWRKY37 was found to be post-translationally phosphorylated at Ser65, a modification crucial for its transcriptional activation. Our findings elucidate the regulatory role of SlWRKY37 in seed dormancy, suggesting its potential as a target for gene editing to reduce seed dormancy in tomato 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 Elsevier Masson SAS. All rights reserved.)

Background: Protein hydrolysates (PHs) can enhance plant nitrogen nutrition and improve the quality of vegetables, depending on their bioactive compounds. A tomato greenhouse experiment was conducted under both optimal (14 mM) and suboptimal (2 mM) nitrogen (N-NO 3 ) conditions. Tomatoes were treated with a new Malvaceae-derived PH (MDPH) and its molecular fractions (MDPH1, >10 kDa; MDPH2, 1-10 kDa and MDPH3, <1 kDa)., Results: Under optimal N conditions, the plants increased biomass and fruit yield, and showed a higher photosynthetic pigment content in leaves in comparison with suboptimal N, whereas under N-limiting conditions, an increase in dry matter, soluble solid content (SSC) and lycopene, a reduction in firmness, and changes in organic acid and phenolic compounds were observed. With 14 mM N-NO 3 , MDPH3 stimulated an increase in dry weight and increased yield components and lycopene in the fruit. The MDPH2 fraction also resulted in increased lycopene accumulation in fruit under 14 mM N-NO 3 . At a low N level, the PH fractions showed distinct effects compared with the whole MDPH and the control, with an increase in biomass for MDPH1 and MDPH2 and a higher pigment content for MDPH3. Regardless of N availability, all the fractions affected fruit quality by increasing SSC, whereas MDPH2 and MDPH3 modified organic acid content and showed a higher concentration of flavonols, lignans, and stilbenes., Conclusion: The molecular weight of the peptides modifies the effect of PHs on plant performance, with different behavior depending on the level of N fertilization, confirming the effectiveness of fractioning processes. © 2024 Society of Chemical Industry., (© 2024 Society of Chemical Industry.)

Methionine (Met) can inhibit plant diseases caused by phytopathogens. However, the effect of Met on gray mold resulted from Botrytis cinerea in tomato is still unclear. This study showed 5 mM Met alleviated disease development of gray mold, enhanced chitinase (CHI) and β-1, 3-glucanase (GNS) activities and the expression of SlCHI, SlGNS, SlPR1 and SlNPR1 in tomatoes, rather than inhibited the growth of B. cinerea directly. Moreover, ethylene biosynthesis and signal transduction before pathogen inoculating were induced by 5 mM Met. Interestingly, Met reduced the nitrosylation levels of ACS4 and ACO6, enhanced the activities of nitric oxide synthase, nitrite reductase (NR) and S-nitrosoglutathione reductase (GSNOR) and the expression of SlNR and SlGSNOR. Tomatoes treated with aminoethoxyvinylglycine and carboxy-PTIO exhibited lower resistance to B. cinerea. These results indicate 5 mM Met promoted ethylene biosynthesis and signal transduction to facilitate NO synthesis and metabolism, enhancing the resistance of tomatoes to B. cinerea., 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. No competing interest., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Members of the MT-A70 family are key catalytic proteins involved in m 6 A methylation modifications in plants. They play diverse roles at the posttranscriptional level by regulating RNA secondary structure, selective splicing, stability, and translational efficiency, which collectively affect plant growth, development, and stress responses. In this study, we explored the function of the gene SlMTC, a Class C member of the MT-A70 family, in tomatoes by using CRISPR/Cas9 technology. Compared with the wild-type (WT), the CR-slmtc mutants exhibited decreased seed size and slower growth rates during the seedling stage, along with weaker salt tolerance and significant downregulation of stress-related genes, such as PR1, PR5, and P5CS. The qRT-PCR results revealed that the expression levels of genes involved in auxin biosynthesis (FZY1, FZY3, and FZY4) and polar transport (PIN1, PIN4, and PIN8) were lower in CR-slmtc plants than in the WT plants. In addition, yeast two-hybrid assays showed that SlMTC could interact with SlMTA, a Class A member of the MT-A70 family, providing insights into the potential mode of action of SlMTC in tomatoes. Overall, our findings indicate the critical role of SlMTC in plant growth and development as well as in response to salt stress., Competing Interests: Declaration of Competing Interest The authors declare that they have no conflict of interest., (Copyright © 2024 Elsevier B.V. All rights reserved.)

To investigate the impact of low temperature on the quality and flavor of ripe red tomatoes, we analyzed transcriptomes and volatile metabolomes of ripe red fruits stored at 0 °C and 20 °C for 8 days. The results showed that 0 °C maintained the sugar content by increasing the expression of sucrose synthetase (SUS) and sucrose transporter (SUT). Low expression of aroma synthesis-related genes, such as alcohol dehydrogenase 1 (ADH1), amino acid decarboxylase 1 A (AADC1A), and branched-chain amino acid aminotransferase 2 (BCAT2), were associated with reduced levels of pentanal, hexanal, 3-methylbutanal, 2-methylbutanal, and 2-phenylethanol. Additionally, the expression of pectinesterase (PE), beta-galactosidase (β-GAL), and beta-glucosidase (β-Glu), as well as phytoene synthase1 (PSY1) involved in carotenoid synthesis, was inhibited, thereby maintaining fruits texture and color. Furthermore, storage at 0 °C induced the expression of numerous genes regulating antioxidant and heat shock proteins, which further preserved the postharvest quality of tomatoes., 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 Ltd.)

Chilling stress is a major environmental factor that significantly reduces crop production. To adapt to chilling stress, plants activate a series of cellular responses and accumulate an array of metabolites, particularly proline. Here, we report that the transcription factor SlWRKY51 increases proline contents in tomato (Solanum lycopersicum) under chilling stress. SlWRKY51 expression is induced under chilling stress. Knockdown or knockout of SlWRKY51 led to chilling-sensitive phenotypes, with lower photosynthetic capacity and more reactive oxygen species (ROS) accumulation than the wild type (WT). The proline contents were significantly reduced in SlWRKY51 knockdown and knockout lines under chilling stress, perhaps explaining the phenotypes of these lines. D-1-pyrroline-5-carboxylate synthetase (P5CS), which catalyses the rate-limiting step of proline biosynthesis, is encoded by two closely related P5CS genes (P5CS1 and P5CS2). We demonstrate that SlWRKY51 directly activates the expression of P5CS1 under chilling stress. In addition, the VQ (a class of plant-specific proteins containing the conserved motif FxxhVQxhTG) family member SlVQ10 physically interacts with SlWRKY51 to enhance its activation of P5CS1. Our study reveals that the chilling-induced transcription factor SlWRKY51 enhances chilling tolerance in tomato by promoting proline accumulation., (© 2024 John Wiley & Sons Ltd.)

Reactive oxygen species (ROS) play a crucial role in regulating numerous functions in organisms. Among the key regulators of ROS production are NADPH oxidases, primarily referred to as respiratory burst oxidase homologues (RBOHs). However, our understanding of whether and how pathogens directly target RBOHs has been limited. In this study, we revealed that the effector protein RipBJ, originating from the phytopathogenic bacterium Ralstonia solanacearum, was present in low- to medium-virulence strains but absent in high-virulence strains. Functional genetic assays demonstrated that the expression of ripBJ led to a reduction in bacterial infection. In the plant, RipBJ expression triggered plant cell death and the accumulation of H 2 O 2 , while also enhancing host defence against R. solanacearum by modulating multiple defence signalling pathways. Through protein interaction and functional studies, we demonstrated that RipBJ was associated with the plant's plasma membrane and interacted with the tomato RBOH known as SlWfi1, which contributed positively to RipBJ's effects on plants. Importantly, SlWfi1 expression was induced during the early stages following R. solanacearum infection and played a key role in defence against this bacterium. This research uncovers the plant RBOH as an interacting target of a pathogen's effector, providing valuable insights into the mechanisms of plant defence., (© 2024 John Wiley & Sons Ltd.)

The bHLH transcription factors are important plant regulators against abiotic stress and involved in plant growth and development. In this study, SlALC , a gene coding for a prototypical DNA-binding protein in the bHLH family, was isolated, and SlALC -overexpression tomato ( SlALC -OE) plants were generated by Agrobacterium-mediated genetic transformation. SlALC transgenic lines manifested higher osmotic stress tolerance than the wild-type plants, estimated by higher relative water content and lower water loss rate, higher chlorophyll, reducing sugar, starch, proline, soluble protein contents, antioxidant enzyme activities, and lower MDA and reactive oxygen species contents in the leaves. In SlALC -OE lines, there were more significant alterations in the expression of genes associated with stress. Furthermore, SlALC -OE fruits were more vulnerable to dehiscence, with higher water content, reduced lignin content, SOD/POD/PAL enzyme activity, and lower phenolic compound concentrations, all of which corresponded to decreased expression of lignin biosynthetic genes. Moreover, the dual luciferase reporter test revealed that SlTAGL1 inhibits SlALC expression. This study revealed that SlALC may play a role in controlling plant tolerance to drought and salt stress, as well as fruit lignification, which influences fruit dehiscence. The findings of this study have established a foundation for tomato tolerance breeding and fruit quality improvement.

Tomato plants favor warmth, making them particularly susceptible to cold conditions, especially their reproductive development. Therefore, understanding how pollen reacts to cold stress is vital for selecting and improving cold-resistant tomato varieties. The programmed cell death (PCD) in the tapetum is particularly susceptible to cold temperatures which could hinder the degradation of the tapetal layer in the anthers, thus affecting pollen development. However, it is not clear yet how genes integral to tapetal degradation respond to cold stress. Here, we report that SlHB8 , working upstream of the conserved genetic module DYT1-TDF1-AMS-MYB80, is crucial for regulating cold tolerance in tomato anthers. SlHB8 expression increases in the tapetum when exposed to low temperatures. CRISPR/Cas9-generated SlHB8-knockout mutants exhibit improved pollen cold tolerance due to the reduced temperature sensitivity of the tapetum. SlHB8 directly upregulates SlDYT1 and SlMYB80 by binding to their promoters. In normal anthers, cold treatment boosts SlHB8 levels, which then elevates the expression of genes like SlDYT1 , SlTDF1 , SlAMS , and SlMYB80 ; however, slhb8 mutants do not show this gene activation during cold stress, leading to a complete blockage of delayed tapetal programmed cell death (PCD). Furthermore, we found that SlHB8 can interact with both SlTDF1 and SlMYB80, suggesting the possibility that SlHB8 might regulate tapetal PCD at the protein level. This study sheds light on molecular mechanisms of anther adaptation to temperature fluctuations.

The REQUIRED FOR ARBUSCULAR MYCORRHIZATION1 (RAM1) transcription factor from the GRAS family is well known for its role as a master regulator of the arbuscular mycorrhizal (AM) symbiosis in dicotyledonous and monocotyledonous species, being essential in transcriptional reprogramming for the development and functionality of the arbuscules. In tomato, SlGRAS27 is the putative orthologue of RAM1 (here named SlRAM1), but has not yet been characterized. A reduced colonization of the root and impaired arbuscule formation were observed in SlRAM1-silenced plants, confirming the functional conservation of the RAM1 orthologue in tomato. However, unexpectedly, SlRAM1-overexpressing (UBIL:SlRAM1) plants also showed decreased mycorrhizal colonization. Analysis of non-mycorrhizal UBIL:SlRAM1 roots revealed an overall regulation of AM-related genes and a reduction of strigolactone biosynthesis. Moreover, external application of the strigolactone analogue GR244DO almost completely reversed the negative effects of SlRAM1 overexpression on the frequency of mycorrhization. However, it only partially recovered the pattern of arbuscule distribution observed in control plants. Our results strongly suggest that SlRAM1 has a dual regulatory role during mycorrhization and, in addition to its recognized action as a positive regulator of arbuscule development, it is also involved in different mechanisms for the negative regulation of mycorrhization, including the repression of strigolactone biosynthesis., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Society for Experimental Biology.)

Heat stress inhibits plant growth and productivity. Among the main regulators, B-box zinc-finger (BBX) proteins are well-known for their contribution to plant photomorphogenesis and responses to abiotic stress. Our research pinpoints that SlBBX31, a BBX protein harboring a conserved B-box domain, serves as a suppressor of plant growth and heat tolerance in tomato ( Solanum lycopersicum L.). Overexpressing (OE) SlBBX31 in tomato exhibited yellowing leaves due to notable reduction in chlorophyll content and net photosynthetic rate (Pn). Furthermore, the pollen viability of OE lines obviously decreased and fruit bearing was delayed. This not only affected the fruit setting rate and the number of plump seeds but also influenced the size of the fruit. These results indicate that SlBBX31 may be involved in the growth process of tomato, specifically in terms of photosynthesis, flowering, and the fruiting process. Conversely, under heat-stress treatment, SlBBX31 knockout (KO) plants displayed superior heat tolerance, evidenced by their improved membrane stability, heightened antioxidant enzyme activities, and reduced accumulation of reactive oxygen species (ROS). Further transcriptome analysis between OE lines and KO lines under heat stress revealed the impact of SlBBX31 on the expression of genes linked to photosynthesis, heat-stress signaling, ROS scavenging, and hormone regulation. These findings underscore the essential role of SlBBX31 in regulating tomato growth and heat-stress resistance and will provide valuable insights for improving heat-tolerant tomato varieties.