Whitefly Bemisia Tabaci Species Complex Research Articles

Bemisia tabaci Vesicle-Associated Membrane Protein 2 Interacts with Begomoviruses and Plays a Role in Virus Acquisition.

Begomoviruses cause substantial losses to agricultural production, especially in tropical and subtropical regions, and are exclusively transmitted by members of the whitefly Bemisia tabaci species complex. However, the molecular mechanisms underlying the transmission of begomoviruses by their whitefly vector are not clear. In this study, we found that B. tabaci vesicle-associated membrane protein 2 (BtVAMP2) interacts with the coat protein (CP) of tomato yellow leaf curl virus (TYLCV), an emergent begomovirus that seriously impacts tomato production globally. After infection with TYLCV, the transcription of BtVAMP2 was increased. When the BtVAMP2 protein was blocked by feeding with a specific BtVAMP2 antibody, the quantity of TYLCV in B. tabaci whole body was significantly reduced. BtVAMP2 was found to be conserved among the B. tabaci species complex and also interacts with the CP of Sri Lankan cassava mosaic virus (SLCMV). When feeding with BtVAMP2 antibody, the acquisition quantity of SLCMV in whitefly whole body was also decreased significantly. Overall, our results demonstrate that BtVAMP2 interacts with the CP of begomoviruses and promotes their acquisition by whitefly.

A proteomic approach reveals possible molecular mechanisms and roles for endosymbiotic bacteria in begomovirus transmission by whiteflies.

BackgroundMany plant viruses are vector-borne and depend on arthropods for transmission between host plants. Begomoviruses, the largest, most damaging and emerging group of plant viruses, infect hundreds of plant species, and new virus species of the group are discovered each year. Begomoviruses are transmitted by members of the whitefly Bemisia tabaci species complex in a persistent-circulative manner. Tomato yellow leaf curl virus (TYLCV) is one of the most devastating begomoviruses worldwide and causes major losses in tomato crops, as well as in many agriculturally important plant species. Different B. tabaci populations vary in their virus transmission abilities; however, the causes for these variations are attributed among others to genetic differences among vector populations, as well as to differences in the bacterial symbionts housed within B. tabaci.ResultsHere, we performed discovery proteomic analyses in 9 whitefly populations from both Middle East Asia Minor I (MEAM1, formerly known as B biotype) and Mediterranean (MED, formerly known as Q biotype) species. We analysed our proteomic results on the basis of the different TYLCV transmission abilities of the various populations included in the study. The results provide the first comprehensive list of candidate insect and bacterial symbiont (mainly Rickettsia) proteins associated with virus transmission.ConclusionsOur data demonstrate that the proteomic signatures of better vector populations differ considerably when compared with less efficient vector populations in the 2 whitefly species tested in this study. While MEAM1 efficient vector populations have a more lenient immune system, the Q efficient vector populations have higher abundance of proteins possibly implicated in virus passage through cells. Both species show a strong link of the facultative symbiont Rickettsia to virus transmission.

Conservation of transcriptional elements in the obligate symbiont of the whitefly Bemisia tabaci.

BackgroundBacterial symbiosis is widespread in arthropods, especially in insects. Some of the symbionts undergo a long-term co-evolution with the host, resulting in massive genome decay. One particular consequence of genome decay is thought to be the elimination of transcriptional elements within both the coding region and intergenic sequences. In the whitefly Bemisia tabaci species complex, the obligate symbiont Candidatus Portiera aleyrodidarum is of vital importance in nutrient provision, and yet little is known about the regulatory capacities of it.MethodsPortiera genomes of two whitefly species in China were sequenced and assembled. Gene content of these two Portiera genomes was predicted, and then subjected to Kyoto Encyclopedia of Genes and Genomes pathway analysis. Together with two other Portiera genomes from whitefly species available previously, four Portiera genomes were utilized to investigate regulatory capacities of Portiera, focusing on transcriptional elements, including genes related with transcription and functional elements within the intergenic spacers.ResultsComparative analyses of the four Portiera genomes of whitefly B. tabaci indicate that the obligate symbionts Portiera is similar in different species of whiteflies, in terms of general genome features and possible functions in the biosynthesis of essential amino acids. The screening of transcriptional factors suggests compromised ability of Portiera to regulate the essential amino acid biosynthesis pathways. Meanwhile, thermal tolerance ability of Portiera is indicated with the detection of a σ32 factor, as well as two predicted σ32 binding sites. Within intergenic spacers, functional elements are predicted, including 37 Shine-Dalgarno sequences and 34 putative small RNAs.

Roles of mating behavioural interactions and life history traits in the competition between alien and indigenous whiteflies

Interference competition between closely related alien and indigenous species often influences the outcome of biological invasions. The whitefly Bemisia tabaci species complex contains ≥28 putative species and two of them, Mediterranean (MED, formally referred to as the 'Q biotype') and Middle East-Asia Minor 1 (MEAM1, formally referred to as the 'B biotype'), have recently spread to much of the world. In many invaded regions, these species have displaced closely related indigenous whitefly species. In this study, we integrated laboratory population experiments, behavioural observations and simulation modelling to investigate the capacity of MED to displace Asia II 1 (AII1, formally referred to as the 'ZHJ2 biotype'), an indigenous whitefly widely distributed in Asia. Our results show that intensive mating interactions occur between MED and AII1, leading to reduced fecundity and progeny female ratio in AII1, as well as an increase in progeny female ratio in MED. In turn, our population cage experiments demonstrated that MED has the capacity to displace AII1 in a few generations. Using simulation models, we then show that both asymmetric mating interactions and differences in life history traits between the two species contribute substantially to the process of displacement. These findings would help explain the displacement of AII1 by MED in the field and, together with earlier studies on mating interactions between other species of the B. tabaci complex, indicate the widespread significance of asymmetric mating interactions in whitefly species exclusions.

Diversity and Genetic Differentiation of the Whitefly Bemisia tabaci Species Complex in China Based on mtCOI and cDNA-AFLP Analysis

The whitefly Bemisia tabaci are considered as a taxonomically complex that contained some destructive pests. Two of the most prevalent cryptic species are B. tabaci Middle East-Asia Minor 1 (MEAM1) and Mediterranean (MED). In an extensive field survey of the B. tabaci complex present throughout part of China from 2004 to 2007, we obtained 93 samples of B. tabaci from 22 provinces. We determined that these Chinese haplotypes included 2 invasive species (MEAM1 and MED), and 4 indigenous cryptic species (Asia II 1, Asia II 3, China 3 and Asia II 7) by sequencing mitochondrial cytochrome oxidose one gene (mtCOI). The diversity and genetic differentiation of a subset of 19 populations of B. tabaci were studied using cDNA amplified fragment length polymorphism (AFLP). Prior to 2007, MEAM1 was a dominant species in many provinces in China. By 2007, MED was dominant in 11 provinces. Both invasive and indigenous species were simultaneously found in some regions. Indigenous species of B. tabaci were found in six provinces in southern China. MED and MEAM1 have broad ranges of host plants, and indigenous species appeared to have much narrower host ranges. All Asia II 3 samples were found on cotton except one on aubergine. China 3 has more host plants than Asia II 3. Twelve samples of China 3 were collected from sweet potato, Japanese hop, squash and cotton. A total of 677 reproducible bands amplified with 5 AFLP primer combinations were obtained. The highest proportion of polymorphic bands was 98.7% and the lowest was 91.9%. Unweighted pair-group method analysis indicated that the clustering was independent of the different species. MED showed the lowest degree of similarity than the other species. The data indicate that both MEAM1and MED were rapidly established in China.

CDNA Cloning of Heat Shock Protein Genes and Their Expression in an Indigenous Cryptic Species of the Whitefly Bemisia tabaci Complex from China

Thermal adaptation plays a fundamental role in shaping the distribution and abundance of insects, and heat shock proteins (Hsps) play important roles in the temperature adaptation of various organisms. To better understand the temperature tolerance of the indigenous ZHJ2-biotype of whitefly Bemisia tabaci species complex, we obtained complete cDNA sequences for hsp90, hsp70, and hsp20 and analyzed their expression profiles under different high temperature treatments by real-time quantitative polymerase chain reaction. The high temperature tolerance of B. tabaci ZHJ2-biotype was determined by survival rate after exposure to different high temperatures for 1 h. The results showed that after 41°C heat-shock treatment for 1 h, the survival rates of ZHJ2 adults declined significantly and the estimated temperature required to cause 50% mortality (LT50) is 42.85°C for 1 h. Temperatures for onset (Ton) or maximal (Tmax) induction of hsps expression in B. tabaci ZHJ2-biotype were 35 and 39°C (or 41°C). Compared with previous studies, indigenous ZHJ2-biotype exhibits lower heat temperature stress tolerance and Ton (or Tmax) than the invasive B-biotype.

Transcriptome analysis and comparison reveal divergence between two invasive whitefly cryptic species

BackgroundInvasive species are valuable model systems for examining the evolutionary processes and molecular mechanisms associated with their specific characteristics by comparison with closely related species. Over the past 20 years, two species of the whitefly Bemisia tabaci species complex, Middle East-Asia Minor 1 (MEAM1) and Mediterranean (MED), have both spread from their origin Middle East/Mediterranean to many countries despite their apparent differences in many life history parameters. Previously, we have sequenced the transcriptome of MED. In this study, we sequenced the transcriptome of MEAM1 and took a comparative genomic approach to investigate the transcriptome evolution and the genetic factors underlying the differences between MEAM1 and MED.ResultsUsing Illumina sequencing technology, we generated 17 million sequencing reads for MEAM1. These reads were assembled into 57,741 unique sequences and 15,922 sequences were annotated with an E-value above 10-5. Compared with the MED transcriptome, we identified 3,585 pairs of high quality orthologous genes and inferred their sequence divergences. The average differences in coding, 5' untranslated and 3' untranslated region were 0.83%, 1.66% and 1.43%, respectively. The level of sequence divergence provides additional support to the proposition that MEAM1 and MED are two species. Based on the ratio of nonsynonymous and synonymous substitutions, we identified 24 sequences that have evolved in response to positive selection. Many of those genes are predicted to be involved in metabolism and insecticide resistance which might contribute to the divergence of the two whitefly species.ConclusionsOur data present a comprehensive sequence comparison between the two invasive whitefly species. This study will provide a road map for future investigations on the molecular mechanisms underlying their biological differences.