Pleiotropic Roles of the Orthologue of the Drosophila melanogaster Intersex Gene in the Brown Planthopper

Abstract

<i>Intersex</i>(<i>ix</i>), a gene involved in the sex-determining cascade of <i>Drosophila melanogaster</i>, works in concert with the female-specific product of <i>doublesex</i> (<i>dsx</i>) at the end of the hierarchy to implement the sex-specific differentiation of sexually dimorphic characters in female individuals. In this study, the <i>ix</i> homolog was identified in the brown planthopper (BPH), <i>Nilaparvata lugens</i>, which contained two splice variants expressed in both female and male insects. We found that <i>Nlix</i> played a vital role in the early nymphal development of BPH, showing an accumulated effect. RNAi-mediated knockdown of <i>Nlix</i> at 4th instar led to the external genital defects in both sexes, consequently resulting in the loss of reproductive ability in female and male individuals. After dsRNA injection, the males were normal on testes, while the females had defective ovarian development. <i>Nlix</i> was also required for early embryogenesis. Notably, when the ds<i>Nlix</i> microinjection was performed in newly emerged females, the copulatory bursas were abnormally enlarged while the other tissues of the reproductive system developed normally. Our results demonstrated the pleiotropic roles of <i>Nlix</i> in embryogenesis and development of the reproductive system in a hemimetabolous insect species.