Search

Plants face constant threats from insect herbivores, which limit plant distribution and abundance in nature and crop productivity in agricultural ecosystems. In recent decades, the whitefly Bemisia tabaci, a group of phloem-feeding insects, has emerged as pests of global significance. In this article, we summarize current knowledge on plant defenses against whitefly and approaches to engineer plant resistance to whitefly. Physically, plants deploy trichome and acylsugar-based strategies to restrain nutrient extraction by whitefly. Chemically, toxic secondary metabolites such as terpenoids confer resistance against whitefly in plants. Moreover, the jasmonate (JA) signaling pathway seems to be the major regulator of whitefly resistance in many plants. We next review advances in interfering with whitefly-plant interface by engineering of plant resistance using conventional and biotechnology-based breeding. These breeding programs have yielded many plant lines with high resistance against whitefly, which hold promises for whitefly control in the field. Finally, we conclude with an outlook on several issues of particular relevance to the nature and engineering of plant resistance against whitefly. [ABSTRACT FROM AUTHOR]

Viruses pose a great threat to animal and plant health worldwide, with many being dependent on insect vectors for transmission between hosts. While the virus–host arms race has been well established, how viruses and insect vectors adapt to each other remains poorly understood. Begomoviruses comprise the largest genus of plantinfecting DNA viruses and are exclusively transmitted by the whitefly Bemisia tabaci. Here, we show that the vector Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway plays an important role in mediating the adaptation between the begomovirus tomato yellow leaf curl virus (TYLCV) and whiteflies. We found that the JAK/STAT pathway in B. tabaci functions as an antiviral mechanism against TYLCV infection in whiteflies as evidenced by the increase in viral DNA and coat protein (CP) levels after inhibiting JAK/STAT signaling. Two STAT-activated effector genes, BtCD109-2 and BtCD109-3, mediate this anti-TYLCV activity. To counteract this vector immunity, TYLCV has evolved strategies that impair the whitefly JAK/STAT pathway. Infection of TYLCV is associated with a reduction of JAK/STAT pathway activity in whiteflies. Moreover, TYLCV CP binds to STAT and blocks its nuclear translocation, thus, abrogating the STAT-dependent transactivation of target genes. We further show that inhibition of the whitefly JAK/STAT pathway facilitates TYLCV transmission but reduces whitefly survival and fecundity, indicating that this JAK/STAT-dependent TYLCV–whitefly interaction plays an important role in keeping a balance between whitefly fitness and TYLCV transmission. This study reveals a mechanism of plant virus–insect vector coadaptation in relation to vector survival and virus transmission. [ABSTRACT FROM AUTHOR]

The whitefly Bemisia tabaci is one of the world's most important invasive crop pests, possibly because it manipulates plant defense signaling. Upon infestation by whiteflies, plants mobilize salicylic acid (SA)-dependent defenses, which mainly target pathogens. In contrast, jasmonic acid (JA)-dependent defenses are gradually suppressed in whitefly-infested plants. The down-regulation of JA defenses make plants more susceptible to insects, including whiteflies. Here, we report that this host-plant manipulation extends to neighboring plants via airborne signals. Plants respond to insect attack with the release of a blend of inducible volatiles. Perception of these volatiles by neighboring plants usually primes them to prepare for an imminent attack. Here, however, we show that whitefly-induced tomato plant volatiles prime SA-dependent defenses and suppress JA-dependent defenses, thus rendering neighboring tomato plants more susceptible to whiteflies. Experiments with volatiles from caterpillar-damaged and pathogeninfected plants, as well as with synthetic volatiles, confirm that whiteflies modify the quality of neighboring plants for their offspring via whitefly-inducible plant volatiles. [ABSTRACT FROM AUTHOR]

The majority of plant viruses are transmitted by insect vectors between hosts, and transovarial transmission of viruses from vector parents to offspring has great significance to their epidemiology. Begomoviruses are transmitted by the whitefly Bemisia tabaci in a circulative manner and are maintained through a plant- insect-plant cycle. Other routes of begomovirus transmission are not clearly known. Here, we report that transovarial transmission from female whiteflies to offspring often happens for one begomovirus, Tomato yellow leaf curl virus (TYLCV), and may have contributed significantly to its global spread. We found that TYLCV entry of the reproductive organ of its vector mainly depended on the developmental stage of the whitefly ovary, and the transovarial transmission of TYLCV to offspring increased with whitefly adult age. The specific interaction between virus coat protein (CP) and whitefly vitellogenin (Vg) was vital for virus entry into whitefly ovary. When knocking down the expression of Vg, the entry of TYLCV into ovary was inhibited and the transovarial transmission efficiency decreased. In contrast, another begomovirus, Papaya leaf curl China virus (PaLCuCNV), CP did not interact with whitefly Vg, and PaLCuCNV could not be transovarially transmitted by whiteflies. We further showed that TYLCV could be maintained for at least two generations in the absence of virusinfected plants, and the adult progenies were able to infect healthy plants in both the laboratory and field. This study reports the transovarial transmission mechanism of begomoviruses, and it may help to explain the evolution and global spread of some begomoviruses. [ABSTRACT FROM AUTHOR]

The whitefly Bemisia tabaci is a major pest to agricultural crops. It transmits begomoviruses, such as Tomato yellow leaf curl virus (TYLCV), in a circular, persistent fashion. Transcriptome analyses revealed that B. tabaci knottin genes were responsive to various stresses. Upon ingestion of tomato begomoviruses, two of the four knottin genes were upregulated, knot-1 (with the highest expression) and knot-3. In this study, we examined the involvement of B. tabaci knottin genes in relation to TYLCV circulative transmission. Knottins were silenced by feeding whiteflies with knottin dsRNA via detached tomato leaves. Large amounts of knot-1 transcripts were present in the abdomen of whiteflies, an obligatory transit site of begomoviruses in their circulative transmission pathway; knot-1 silencing significantly depleted the abdomen from knot-1 transcripts. Knot-1 silencing led to an increase in the amounts of TYLCV ingested by the insects and transmitted to tomato test plants by several orders of magnitude. This effect was not observed following knot-3 silencing. Hence, knot-1 plays a role in restricting the quantity of virions an insect may acquire and transmit. We suggest that knot-1 protects B. tabaci against deleterious effects caused by TYLCV by limiting the amount of virus associated with the whitefly vector. [ABSTRACT FROM AUTHOR]

Background: The begomoviruses are the largest and most economically important group of plant viruses exclusively vectored by whitefly (Bemisia tabaci) in a circulative, persistent manner. During this process, begomoviruses and whitefly vectors have developed close relationships and complex interactions. However, the molecular mechanisms underlying these interactions remain largely unknown, and the microRNA profiles for viruliferous and nonviruliferous whiteflies have not been studied. Methods: Sequences of Argonaute 1(Ago1) and Dicer 1 (Dcr1) genes were cloned from B. tabaci MEAM1 cDNAs. Subsequently, deep sequencing of small RNA libraries from uninfected and Tomato yellow leaf curl China virus (TYLCCNV)-infected whiteflies was performed. The conserved and novel miRNAs were identified using the release of miRBase Version 19.0 and the prediction software miRDeep2, respectively. The sequencing results of selected deregulated and novel miRNAs were further confirmed using quantitative reverse transcription-PCR. Moreover, the previously published B. tabaci MEAM1 transcriptome database and the miRNA target prediction algorithm miRanda 3.1 were utilized to predict potential targets for miRNAs. Gene Ontology (GO) analysis was also used to classify the potential enriched functional groups of their putative targets. Results: Ago1 and Dcr1orthologs with conserved domains were identified from B. tabaci MEAM1. BLASTn searches and sequence analysis identified 112 and 136 conserved miRNAs from nonviruliferous and viruliferous whitefly libraries respectively, and a comparison of the conserved miRNAs of viruliferous and nonviruliferous whiteflies revealed 15 up- and 9 down-regulated conserved miRNAs. 7 novel miRNA candidates with secondary pre-miRNA hairpin structures were also identified. Potential targets of conserved and novel miRNAs were predicted using GO analysis, for the targets of up- and down-regulated miRNAs, eight and nine GO terms were significantly enriched. Conclusions: We identified Ago1 and Dcr1 orthologs from whiteflies, which indicated that miRNA-mediated silencing is present in whiteflies. Our comparative analysis of miRNAs from TYLCCNV viruliferous and nonviruliferous whiteflies revealed the relevance of deregulated miRNAs for the post-transcriptional gene regulation in these whiteflies. The potential targets of all expressed miRNAs were also predicted. These results will help to acquire a better understanding of the molecular mechanism underlying the complex interactions between begomoviruses and whiteflies. [ABSTRACT FROM AUTHOR]

Background: The whitefly Bemisia tabaci is an important agricultural pest with global distribution. This phloem-sap feeder harbors a primary symbiont, "Candidatus Portiera aleyrodidarum", which compensates for the deficient nutritional composition of its food sources, and a variety of secondary symbionts. Interestingly, all of these secondary symbionts are found in co-localization with the primary symbiont within the same bacteriocytes, which should favor the evolution of strong interactions between symbionts. Results: In this paper, we analyzed the genome sequences ofthe primary symbiont Portiera and ofthe secondary symbiont Hamiltonella in the B. tabaci Mediterranean (MED) species in order to gain insight into the metabolic role of each symbiont in the biology of their host. The genome sequences of the uncultured symbionts Portiera and Hamiltonella were obtained from one single bacteriocyte of MED B. tabaci. As already reported, the genome of Portiera is highly reduced (357 kb), but has kept a number of genes encoding most essential amino-acids and carotenoids. On the other hand, Portiera lacks almost all the genes involved in the synthesis of vitamins and cofactors. Moreover, some pathways are incomplete, notably those involved in the synthesis of some essential amino-acids. Interestingly, the genome of Hamiltonella revealed that this secondary symbiont can not only provide vitamins and cofactors, but also complete the missing steps of some of the pathways of Portiera. In addition, some critical amino-acid biosynthetic genes are missing in the two symbiotic genomes, but analysis of whitefly transcriptome suggests that the missing steps may be performed by the whitefly itself or its microbiota. Conclusions: These data suggest that Portiera and Hamiltonella are not only complementary but could also be mutually dependent to provide a full complement of nutrients to their host. Altogether, these results illustrate how functional redundancies can lead to gene losses in the genomes ofthe different symbiotic partners, reinforcing their inter-dependency. [ABSTRACT FROM AUTHOR]

Bacterial endosymbiosis is an important evolutionary process in insects, which can harbor both obligate and facultative symbionts. The evolution of these symbionts is driven by evolutionary convergence, and they exhibit among the tiniest genomes in prokaryotes. The large host spectrum of facultative symbionts and the high diversity of strategies they use to infect new hosts probably impact the evolution of their genome and explain why they undergo less severe genomic erosion than obligate symbionts. Candidatus Hamiltonella defensa is suitable for the investigation of the genomic evolution of facultative symbionts because the bacteria are engaged in specific relationships in two clades of insects. In aphids, H. defensa is found in several species with an intermediate prevalence and confers protection against parasitoids. In whiteflies, H. defensa is almost fixed in some species of Bemisia tabaci, which suggests an important role of and a transition toward obligate symbiosis. In this study, comparisons of the genome of H. defensa present in two B. tabaci species (Middle East Asia Minor 1 and Mediterranean) and in the aphid Acyrthosiphon pisum revealed that they belong to two distinct clades and underwent specific gene losses. In aphids, it contains highly virulent factors that could allow protection and horizontal transfers. In whiteflies, the genome lost these factors and seems to have a limited ability to acquire genes. However it contains genes that could be involved in the production of essential nutrients, which is consistent with a primordial role for thissymbiont. In conclusion, although both lineages of H. defensa have mutualistic interactions with their hosts, their genomes follow distinct evolutionary trajectories that reflect their phenotype and could have important consequences on their evolvability. [ABSTRACT FROM AUTHOR]

c-Jun NH2-terminal kinase (JNK) signaling is a highly conserved pathway that controls gene transcription in response to a wide variety of biological and environmental stresses. In this study, a JNK from the invasive Mediterranean (MED) species of the whitefly Bemisia tabaci complex was cloned and characterized. The full-length JNK cDNA of MED consists of 1565 bp, with an 1176 bp open reading frame encoding 392 amino acids. Comparison of JNK amino acid sequences among different species showed that the sequences of JNKs are highly conserved. To reveal its biological function, the gene expression and functional activation of JNK were analyzed during various stress conditions. Quantitative RT-PCR analysis showed that the relative expression level of JNK remained hardly unchanged when the insects were transferred from cotton (a suitable host plant) to tobacco (an unsuitable host plant), infected with bacteria and treated with high and low temperatures. However, the mRNA level of JNK significantly increased when treated with fungal pathogens. Furthermore, we found that the amount of phosphorylated JNK increased significantly after fungal infection, while there is no obvious change for phosphorylated p38 and ERK. Our results indicate that the whitefly JNK plays an important role in whitefly's immune responses to fungal infection [ABSTRACT FROM AUTHOR]

Background: The whiteflies under the name Bemisia tabaci (Gennadius) (Aleyrodidae: Hemiptera) are species complex of at least 31 cryptic species some of which are globally invasive agricultural pests. Previously, the mitochondrial genome (mitogenome) of the indigenous New World B. tabaci species was sequenced and major differences of gene order from the postulated whitefly ancestral gene order were found. However, the sequence and gene order of mitogenomes in other B. tabaci species are unknown. In addition, the sequence divergences and gene expression profiles of mitogenomes in the B. tabaci species complex remain completely unexplored. Results: In this study, we obtained the complete mitogenome (15,632 bp) of the invasive Mediterranean (MED), which has been identified as the type species of the B. tabaci complex. It encodes 37 genes, including 13 proteincoding genes (PCGs), 2 ribosomal RNAs and 22 transfer RNAs (tRNA). Comparative analyses of the mitogenomes from MED and New World (previously published) species reveal that there are no gene arrangements. Based on the Illumina sequencing data, the gene expression profile of the MED mitogenome was analyzed. We found that a number of genes were polyadenylated and the partial stop codons in cox1, cox2 and nd5 are completed via polyadenylation that changed T to the TAA stop codon. In addition, combining the transcriptome with the sequence alignment data, the possible termination site of some PCGs were defined. Our analyses also revealed that atp6 and atp8, nd4 and nd4l, nd6 and cytb were found on the same cistronic transcripts, whereas the other mature mitochondrial transcripts were monocistronic. Furthermore, RT-PCR analyses of the mitochondrial PCGs expression in different developmental stages revealed that the expression level of individual mitochondrial genes varied in each developmental stage of nymph, pupa and adult. Interestingly, mRNA levels showed significant differences among genes located in the same transcription unit suggesting that mitochondrial mRNA abundance is heavily modulated by post-transcriptional regulation. Conclusions: This work provides novel insights into the mitogenome evolution of B. tabaci species and demonstrates that utilizing RNA-seq data to obtain the mitogenome and analyze mitochondrial gene expression characteristics is practical. [ABSTRACT FROM AUTHOR]

Quantitative real-time reverse transcription polymerase chain reaction is widely used for gene expression analysis, and robust normalization against stably expressed endogenous reference genes (ERGs) is necessary to obtain accurate results. In this study, the stability of nine housekeeping genes of the sweetpotato whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae) Mediterranean were evaluated in various conditions by quantitative real-time reverse transcription polymerase chain reaction using geNorm and Normfinder programs. Both programs suggested α-tubulin/ubiquitin and 18S small subunit ribosomal RNA the most stable genes for bacterium- and insecticide-treated whiteflies, respectively. For developmental stages, organs, and the samples including salivary glands and the whole body, transcription initiation factor TFIID subunit was calculated as the most stably expressed gene by both programs. In addition, we compared the RNA-seq data with the results of geNorm and Normfinder and found that the stable genes revealed by RNA-seq analysis were also the ERGs recommended by geNorm and Normfinder. Furthermore, the use of the most stable gene suggested by RNA-seq analysis as an ERG produced similar gene expression patterns compared with results generated from the normalization against the most stable gene selected by geNorm and Normfinder and multiple genes recommended by geNorm. It indicates that RNA-seq data are reliable and provide a great source for ERG candidate exploration. Our results benefit future research on gene expression profiles of whiteflies and possibly other organisms. [ABSTRACT FROM AUTHOR]

Background: The MEAM1 (B biotype) Bemisia tabaci (Gennadius) is one of the most widespread and damaging whitefly cryptic species. Our previous studies discovered that the MEAM1 whitefly indirectly benefits from interactions with the tomato yellow leaf curl China virus (TYLCCNV) via accelerated ovarian development and increased fecundity. However, the physiological mechanism of begomoviruse-infected plants acting on the reproduction of the insect vector was unknown. Methodology/Principal Findings: Biochemical and molecular properties of vitellogenin (Vg) and vitellin (Vt) were characterized in the MEAM1 whitefly. In addition, kinetics of Vt levels in ovary and Vg levels in hemolymph in different stages were detected using a sandwich ELISA. The level of hemolymph Vg increased rapidly after eclosion. A significantly higher level of hemolymph Vg and ovary Vt were observed in whiteflies feeding on virus-infected tobacco plants than those feeding on uninfected plants. In order to detect the levels of Vg mRNA transcription, complete vitellogenin (Vg) mRNA transcripts of 6474 bp were sequenced. Vg mRNA level in whiteflies feeding on virus-infected plants was higher than those feeding on uninfected plants. However, virus-infection of the whiteflies per se, as demonstrated using an artificial diet system, did not produce significant changes in Vg mRNA level. Conclusions/Significance: In MEAM1 whitefly, increased levels of both vitellin and vitellogenin as well as increased transcription of Vg mRNA are associated with feeding on begomovirus- infected plants, thus providing a mechanism for accelerated vitellogenesis. We conclude that MEAM1 whitefly profits from feeding on begomovirus-infected plants for yolk protein synthesis and uptake, and thereby increases its fecundity. These results not only provide insights into the molecular and physiological mechanisms underlying the elevated reproduction of a whitefly species through its association with a begomovirus-infected plant, but also provide a better understanding of the molecular mechanisms related to whitefly reproduction. [ABSTRACT FROM AUTHOR]

Background: Some species of the whitefly Bemisia tabaci complex cause tremendous losses to crops worldwide through feeding directly and virus transmission indirectly. The primary salivary glands of whiteflies are critical for their feeding and virus transmission. However, partly due to their tiny size, research on whitefly salivary glands is limited and our knowledge on these glands is scarce. Methodology/Principal Findings: We sequenced the transcriptome of the primary salivary glands of the Mediterranean species of B. tabaci complex using an effective cDNA amplification method in combination with short read sequencing (Illumina). In a single run, we obtained 13,615 unigenes. The quantity of the unigenes obtained from the salivary glands of the whitefly is at least four folds of the salivary gland genes from other plant-sucking insects. To reveal the functions of the primary glands, sequence similarity search and comparisons with the whole transcriptome of the whitefly were performed. The results demonstrated that the genes related to metabolism and transport were significantly enriched in the primary salivary glands. Furthermore, we found that a number of highly expressed genes in the salivary glands might be involved in secretory protein processing, secretion and virus transmission. To identify potential proteins of whitefly saliva, the translated unigenes were put into secretory protein prediction. Finally, 295 genes were predicted to encode secretory proteins and some of them might play important roles in whitefly feeding. Conclusions/Significance:: The combined method of cDNA amplification, Illumina sequencing and de novo assembly is suitable for transcriptomic analysis of tiny organs in insects. Through analysis of the transcriptome, genomic features of the primary salivary glands were dissected and biologically important proteins, especially secreted proteins, were predicted. Our findings provide substantial sequence information for the primary salivary glands of whiteflies and will be the basis for future studies on whitefly-plant interactions and virus transmission. [ABSTRACT FROM AUTHOR]

The article offers information on the study made by researchers to analyze the mating behaviour of whitefly Bemisia tabaci (B. tabaci). It states that the aspects of mating behaviour impact the competitive interactions between alien and indigenous whiteflies. Scientists closely observed the oviposition and copulation of B. tabaci on leaf subtrates created with the help of different plant species.

Background: To understand the processes of invasions by alien insects is a pre-requisite for improving management. The whitefly Bemisia tabaci is a cryptic species complex that contains some of the most invasive pests worldwide. However, extensive field data to show the geographic distribution of the members of this species complex as well as the invasion by some of its members are scarce. Methodology/Principal Findings: We used field surveys and published data to assess the current diversity and distribution of B. tabaci cryptic species in China and relate the indigenous members to other Asian and Australian members of the complex. The survey covered the 16 provinces where indigenous B. tabaci occur and extends this with published data for the whole of China. We used molecular markers to identify cryptic species. The evolutionary relationships between the different Asian B. tabaci were reconstructed using Bayesian methods. We show that whereas in the past the exotic invader Middle East-Asia Minor 1 was predominant across China, another newer invader Mediterranean is now the dominant species in the Yangtze River Valley and eastern coastal areas, and Middle East-Asia Minor 1 is now predominant only in the south and south eastern coastal areas. Based on mtCO1 we identified four new cryptic species, and in total we have recorded 13 indigenous and two invasive species from China. Diversity was highest in the southern and southeastern provinces and declined to north and west. Only the two invasive species were found in the northern part of the country where they occur primarily in protected cropping. By 2009, indigenous species were mainly found in remote mountainous areas and were mostly absent from extensive agricultural areas. Conclusions/Significance: Invasions by some members of the whitefly B. tabaci species complex can be rapid and widespread, and indigenous species closely related to the invaders are replaced. [ABSTRACT FROM AUTHOR]

Background: Plant-pathogenic begomoviruses have a complex association with their insect vectors. The interactions of begomoviruses and reproduction of their vectors are poorly understood. Bemisia tabaci is known to transmit many begomoviruses, and the spread of B. tabaci, especially the B and Q 'biotypes', has been accompanied by the epidemics of begomoviruses. One of these identified disease-causing agents was Tomato yellow leaf curl China virus (TYLCCNV). Methodology/Principal Findings: In this study, we compared the egg production and realized fecundity of two 'biotypes' or putative species of the whitefly B. tabaci, including the alien invasive B and the indigenous ZHJ1 from Zhejiang, China, feeding on either healthy or TYLCCNV-infected tobacco plants. The ovary of the whitefly was composed of 12-22 telotrophic ovarioles. According to the morphology of the oocytes and level of yolk content, oocytes in ovarioles were divided into four developmental phases (I-IV). Significantly higher proportion of immature oocytes (phase II, III) and mature oocytes (phase IV) was observed in ovary of females that fed on TYLCCNV-infected tobacco compared to that on healthy plants. Moreover, there was significant increase of eggs laid of B whitefly that fed on TYLCCNV-infected tobacco plants during the early developmental stages. In contrast, the proportion of oocytes of different developmental phases and eggs laid had no significant differences between ZHJ1 whiteflies feeding on TYLCCNV-infected and non-infected host plants. Conclusions/Significance: The invasive B whitefly benefits from feeding on a begomovirus-infected plant through increased egg production and realized fecundity. [ABSTRACT FROM AUTHOR]

The whitefly Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) is a species complex, and its systematic classification requires controlled crossing experiments among its genetic groups. Accurate information on pre-copulation intervals, copulation frequencies, and initial frequency of egg fertilization of newly emerged adults is critical for designing procedures for collecting the virgin adults necessary for these experiments. In the literature, considerable variation is reported between B. tabaci populations, with respect to the length of the pre-copulation interval and the initial frequency of egg fertilization. Here, we used a video-recording method to observe continuously the copulation behaviour of the Mediterranean/Asia Minor/Africa (B biotype) and the Asia II (ZHJ1 biotype) groups of B. tabaci. We also recorded the initial frequency of egg fertilization, as determined by the sex of the progeny. When adults were caged in female–male pairs on leaves of cotton plants, the earliest copulation events occurred 2–6 h after emergence; at 12 h after emergence 56–84% of the females had copulated at least once, and nearly all (92–100%) had copulated at least once by 36 h after emergence. Both females and males copulated repeatedly. Approximately 80 and 20% of copulation events occurred during the photophase and scotophase, respectively. By 72 h post-emergence, the females of the B and ZHJ1 biotypes had copulated on average 6.1 and 3.9 times, respectively. When adults were caged in groups on plants 1–13 h after emergence, 30–35% of the eggs deposited during this period were fertilized, and approximately 90% of females were fertilized by the end of the 13 h. Although timing of copulation differed in detail between the two genetic groups, the results demonstrate that B. tabaci adults can start to copulate as early as 2–6 h post-emergence and the majority of females can become fertilized on the day that they emerge. [ABSTRACT FROM AUTHOR]

The article presents a study which investigates the copulation events of whiteflies on plants by using a video camera. Bemisia tabaci is a genetically diverse group with more than 20 biotypes. Newly emerged adult whiteflies were placed in pairs into a clip cage which was attached to a leaf and observed by a video camera. The results indicated that of the 25 virgin B-biotype females, 10 did not mate, 12 mated once and 3 mated more than once.

The objective of this study was to derive a description of the mating behaviour of the whiteflyBemisia tabaci, and to compare this behaviour between the notorious invasive B biotype and a native non-B biotype of the insect from Zhejiang, China. We first did a crossing experiment between the two biotypes, and then conducted observations on the various components of their mating behaviour by continuous recording with video cameras. Reciprocal crossing trials between the two biotypes resulted in no female progeny and thus demonstrated no compatibility in reproduction between them. The whole process of mating could be described as three consecutive phases: male search for female, courtship, and copulation. In both biotypes, successful mating could be completed as early as 4–6 h after emergence and over half the individuals completed their first mating in the first 12 h. The frequency of mating in the B biotype was marginally higher than that in ZHJ1. Moreover, the frequency of mating by females in the B biotype increased by nearly three times when an extra male of the same biotype was added, while addition of an extra male in the ZHJ1 did not result in an increase of mating frequency. These results indicate that individuals of the B biotype have a stronger propensity to mate than that of ZHJ1when the proportion of males in a colony is increased. The stronger propensity and ability for mating in the B biotype may be an advantage in its reproductive competition and interference with non-B biotypes of this insect. [ABSTRACT FROM AUTHOR]

Most plant viruses require a biological vector to spread from plant to plant in nature. Among biological vectors for plant viruses, hemipteroid insects are the most common, including phloem-feeding aphids, whiteflies, mealybugs, planthoppers, and leafhoppers. A majority of the emerging diseases challenging agriculture worldwide are insect borne, with those transmitted by whiteflies (Hemiptera: Aleyrodidae) topping the list. Most damaging whitefly-transmitted viruses include begomoviruses (Geminiviridae), criniviruses (Closteroviridae), and torradoviruses (Secoviridae). Among the whitefly vectors, Bemisia tabaci, now recognized as a complex of cryptic species, is the most harmful in terms of virus transmission. Here, we review the available information on the differential transmission efficiency of begomoviruses and other whitefly-borne viruses by different species of whiteflies, including the cryptic species of the B. tabaci complex. In addition, we summarize the factors affecting transmission of viruses by whiteflies and point out some future research prospects. [ABSTRACT FROM AUTHOR]

The majority of plant viruses are vectored by arthropods via persistent-circulative or noncirculative transmission. Previous studies have shown that specific binding sites for noncirculative viruses reside within the stylet or foregut of insect vectors, whereas the transmission mechanisms of circulative viruses remain ambiguous. Here we report the critical roles of whitefly primary salivary glands (PSGs) in the circulative transmission of two begomoviruses. The Middle East Asia Minor 1 (MEAM1) species of the whitefly Bemisia tabaci complex efficiently transmits both Tomato yellow leaf curl China virus (TYLCCNV) and Tomato yellow leaf curl virus (TYLCV), whereas the Mediterranean (MED) species transmits TYLCV but not TYLCCNV. PCR and fluorescence in situ hybridization experiments showed that TYLCCNV efficiently penetrates the PSGs of MEAM1 but not MED whiteflies. When a fragment of the coat protein of TYLCCNV was exchanged with that of TYLCV, mutated TYLCCNV accumulated in the PSGs of MED whiteflies, while mutant TYLCV was nearly undetectable. Confocal microscopy revealed that virion transport in PSGs follows specific paths to reach secretory cells in the central region, and the accumulation of virions in the secretory region of PSGs was correlated with successful virus transmission. Our findings demonstrate that whitefly PSGs, in particular the cells around the secretory region, control the specificity of begomovirus transmission. [ABSTRACT FROM AUTHOR]

We report the draft genome sequence of the Rickettsia sp. strain MEAM1, which is a facultative symbiont from an invasive species of the whitefly Bemisia tabaci. The total length of the assembled genome is approximately 1.24 Mb, with 335 scaffolds and 1,247 coding sequences predicted within the genome. [ABSTRACT FROM AUTHOR]