Abstract
BackgroundGenomic divergence between invasive and native species may provide insight into the molecular basis underlying specific characteristics that drive the invasion and displacement of closely related species. In this study, we sequenced the transcriptome of an indigenous species, Asia II 3, of the Bemisia tabaci complex and compared its genetic divergence with the transcriptomes of two invasive whiteflies species, Middle East Asia Minor 1 (MEAM1) and Mediterranean (MED), respectively.ResultsMore than 16 million reads of 74 base pairs in length were obtained for the Asia II 3 species using the Illumina sequencing platform. These reads were assembled into 52,535 distinct sequences (mean size: 466 bp) and 16,596 sequences were annotated with an E-value above 10-5. Protein family comparisons revealed obvious diversification among the transcriptomes of these species suggesting species-specific adaptations during whitefly evolution. On the contrary, substantial conservation of the whitefly transcriptomes was also evident, despite their differences. The overall divergence of coding sequences between the orthologous gene pairs of Asia II 3 and MEAM1 is 1.73%, which is comparable to the average divergence of Asia II 3 and MED transcriptomes (1.84%) and much higher than that of MEAM1 and MED (0.83%). This is consistent with the previous phylogenetic analyses and crossing experiments suggesting these are distinct species. We also identified hundreds of highly diverged genes and compiled sequence identify data into gene functional groups and found the most divergent gene classes are Cytochrome P450, Glutathione metabolism and Oxidative phosphorylation. These results strongly suggest that the divergence of genes related to metabolism might be the driving force of the MEAM1 and Asia II 3 differentiation. We also analyzed single nucleotide polymorphisms within the orthologous gene pairs of indigenous and invasive whiteflies which are helpful for the investigation of association between allelic and phenotypes.ConclusionsOur data present the most comprehensive sequences for the indigenous whitefly species Asia II 3. The extensive comparisons of Asia II 3, MEAM1 and MED transcriptomes will serve as an invaluable resource for revealing the genetic basis of whitefly invasion and the molecular mechanisms underlying their biological differences.
Highlights
Genomic divergence between invasive and native species may provide insight into the molecular basis underlying specific characteristics that drive the invasion and displacement of closely related species
Extensive evidence has indicated that the invasion of Middle East Asia Minor 1 (MEAM1) and MED are associated with the displacement of their closely related indigenous whitefly species [8,14]
The contigs were assembled into 77,263 scaffolds and further clustered into 52,535 distinct sequences (Table 1). These results are comparable to the transcriptome of the invasive MEAM1 which contains 104,722 scaffolds and 57,741 distinct sequences with an average length of 479 bp (Additional file 1) [30]
Summary
Genomic divergence between invasive and native species may provide insight into the molecular basis underlying specific characteristics that drive the invasion and displacement of closely related species. We sequenced the transcriptome of an indigenous species, Asia II 3, of the Bemisia tabaci complex and compared its genetic divergence with the transcriptomes of two invasive whiteflies species, Middle East Asia Minor 1 (MEAM1) and Mediterranean (MED), respectively. The whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a species complex composed of at least 31 morphologically indistinguishable cryptic species (hereafter referred to as "species") [1,2,3,4,5,6] These species differ genetically as well as in host range, fecundity, insecticide resistance, mating behavior and ability to transmit begomoviruses [7,8,9,10,11,12]. Extensive evidence has indicated that the invasion of MEAM1 and MED are associated with the displacement of their closely related indigenous whitefly species [8,14]
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