RNAi-Mediated Knockdown of Halloween Genes in Lygus hesperus Has Varied Effects on Oogenesis and Fertility

For many insects, the ecdysteroid biosynthetic pathway that converts cholesterol to ecdysone includes multiple cytochrome P450 monooxygenases, a Rieske oxygenase, and a short-chain dehydrogenase. Collectively, the genes encoding these enzymes are referred to as Halloween genes. While the importance of these enzymes in oogenesis is well-documented in holometabolous insects, less is known about their oogenic role in hemipterans. To address this, we used RNA interference-mediated knockdown to determine the role that the Halloween transcripts neverland, spookiest, shroud, phantom, disembodied, shadow, and shade have on oogenesis and fertility in the western tarnished plant bug, Lygus hesperus Knight. Knockdown of neverland and spookiest severely curtailed oogenesis and resulted in little to no oviposition, phantom knockdown had no impact on oogenesis but reduced oviposition and egg hatch, and shadow knockdown resulted in reduced egg hatch. In contrast, knockdown of shroud, disembodied, and shade had no observable effects on oogenesis, oviposition, or hatch rate. While this study demonstrates the critical reproductive role of some Halloween genes in L. hesperus, it also raises questions regarding how broadly conserved the current ecdysteroid biosynthetic pathway is across insects.