Proteolytic activity of the proteasome is required for female insect reproduction

Abstract

Non-ATPase regulatory subunits (Rpns) are components of the 26S proteasome involved in polyubiquitinated substrate recognition and deubiquitination in eukaryotes. Here, we identified 15 homologues sequences of <i>Rpn</i> and associated genes by searching the genome and transcriptome databases of the brown planthopper, <i>Nilaparvata lugens</i>, a hemipteran rice pest. Temporospatial analysis showed that <i>NlRpn</i> genes were significantly highly expressed in eggs and ovaries but were less-highly expressed in males. RNA interference-mediated depletion of <i>NlRpn</i> genes decreased the proteolytic activity of proteasome and impeded the transcription of <i>lipase</i> and <i>vitellogenin</i> genes in the fat bodies and ovaries in adult females, and reduced the triglyceride content in the ovaries. Decrease of the proteolytic activity of the proteasome via knockdown of <i>NlRpn</i>s also inhibited the transcription of <i>halloween</i> genes, including <i>NlCYP307A2</i>, <i>NlCYP306A2</i> and <i>NlCYP314A1</i>, in the 20-hydroxyecdysone (20E) biosynthetic pathway in the ovaries, reduced 20E production in adult females, and impaired ovarian development and oocyte maturation, resulting in reduced fecundity. These novel findings indicate that the proteolytic activity of the proteasome is required for female reproductive processes in <i>N. lugens</i>, thus furthering our understanding of the reproductive and developmental strategies in insects.