Regulation of NlE74A on vitellogenin may be mediated by angiotensin converting enzyme through a fecundity-related SNP in the brown planthopper, Nilaparvata lugens

Abstract

The major yolk protein precursors (YPP) gene, vitellogenin (Vg), usually considered as a reproductive indicator and molecular marker for evaluating insect fecundity, is controlled by insect hormone (mainly ecdysteroids and juvenile hormone), transcription factors and many other fecundity-related genes. To better understand the underlying molecular regulation mechanisms of the NlVg in the brown planthopper Nilaparvata lugens (N. lugens), the correlation between one early ecdysone response gene E74 and one important fecundity-related gene angiotensin converting enzyme (ACE) on the regulation of Vg gene expression, was investigated. We first showed that the mRNA expression level of NlACE were significantly higher in a high-fecundity population (HFP) than a low-fecundity population (LFP) at different development stages, and knockdown of NlACE expression by RNA interference (RNAi) results in a reduced level of NlVg expression and N. lugens fecundity. Subsequently, we analyzed the promoter of NlACE and found an E74A binding site, which was also differentially expressed in HFP and LFP. Then a gene putatively encoding E74A, namely NlE74A, predominant in the ovary and fat body was cloned and characterized. Furthermore, the developmental profile during female adult and the tissue-specific expression pattern of NlACE and NlE74A were similar to the expression pattern of NlVg gene, implying that both NlACE and NlE74A may be involved in regulating the expression of NlVg. Finally, after injecting the dsRNA of NlE74A, the NlACE expression levels were significantly reduced simultaneously at 24 h and 48 h post-injection, and the NlVg expression level was significant reduced at 24 h post-injection and the downswing was more significant at 48 h post-injection. These results imply that regulation of NlE74A on NlVg transcription might be mediated by NlACE through the E74 binding site at the NlACE promoter region in N. lugens.