<i>Tra-2</i> Mediates Cross-Talk Between Sex Determination and Wing Polyphenism in Female <i>Nilaparvata lugens</i>

Abstract

Sexual dimorphism and wing polyphenism are important and evolutionarily conserved features of many insect species. In this article, we found a cross-talk linking sexual differentiation with wing polyphenism in the brown planthopper (BPH) <i>Nilaparvata lugens</i> (order: Hemiptera). Knockdown of the sex determination gene <i>Transformer-2</i> in <i>N. lugens</i> (<i>NlTra-2</i>) in nymph caused females to develop into infertile pseudomales containing undeveloped ovaries. Whereas males treated with ds<i>NlTra-2</i> exhibited normal morphology, but lost fertility. Knockdown of <i>NlTra-2</i> in adult females (maternal RNAi) resulted in long-winged female offspring, indicating that maternal RNAi changed the wing morphs in female offspring. In addition, silencing of <i>NlTra-2</i> down-regulated the expression of the <i>forkhead</i> transcription factor FoxO (<i>NlFoxO</i>), and simultaneously up-regulated the expression of <i>phosphatidylinositol-3-OH kinase</i> (<i>PI</i>(<i>3</i>)<i>K</i>)<i>-protein kinase B</i> (<i>NlAkt</i>), the two critical genes in the insulin signaling pathway. Furthermore, the long-winged effect caused by maternal ds<i>NlTra-2</i> RNAi could be reversed by silencing of <i>NlInR1</i> and <i>NlAkt</i>, leading to short-winged morphs. We propose that there is a cross-talk between the sexual differentiation and wing polyphenism pathways mediated by <i>NlTra-2</i> during embryonic stages.