Transformer is involved in female sex determination in Bemisia tabaci

Sex determination is one of the fundamental questions in developmental and evolutionary biology. While the upstream regulatory mechanisms governing somatic sex determination in insects are highly divergent, the downstream transformer (tra) + transformer2 (tra2) → doublesex (dsx) pathway is relatively conserved. In the sweet potato whitefly, Bemisia tabaci, a global invasive pest, tra2 and dsx have been previously characterised, revealing their critical role in male genitalia formation. However, the role of tra in B. tabaci sex determination has remained unclear. Here, we characterised Bttra, the B. tabaci transformer, and identified multiple TRA/TRA-2 binding sites and several splice variants. A glutathione S-transferase (GST) pull-down assay confirmed direct interactions between BtTRA and BtTRA2 in vitro. Functional analysis through Bttra silencing demonstrated its regulatory impact on Btdsx expression and its essential role in female development. Our combined findings provide new insights into the function of tra in B. tabaci sex determination, highlighting variation in sex determination among haplodiploid insects. Moreover, this study identifies potential molecular targets for the future management of this devastating insect pest.