The silverleaf whitefly Bemisia tabaci is one of the most destructive of crop pests globally. In Northern India cotton is predominately infested by the Asia II-1 species of B. tabaci. Though B. tabaci exhibits unique haplodiploidy in its reproductive behavior, to date very little is known regarding its sex determination mechanism. Here, an in-depth characterization of the AsiaII-1 doublesex (Btdsx) gene, which has been implicated in sex determination in B. tabaci, indicates the inclusion of six exons and five introns. The pre-mRNA is shown to sex-specifically splice, producing four male isoforms and one female isoform. These BtDsx proteins share common DNA binding (OD1) domains whereas they differ at their C-termini. RT-qPCR analysis revealed a significantly higher expression of Btdsx in female adults compared to that in male adults and earlier developmental stages. Functional characterization of Btdsx through RNA interference (RNAi) resulted in a significant reduction in its expression in both sexes. Btdsx knockdown concomitantly resulted in up-regulation of the expression of vitellogenin (vg) and vitellogenin receptor (vgr) genes in males and their down-regulation in females. Btdsx knockdown followed by mating resulted in reduced fecundity and percent egg hatching; however, no impact was observed on the female: male ratios in the progeny obtained from knockdown parents.
Keywords: Bemisia tabaci; Doublesex; Sex specific splicing; dsRNA feeding.
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