Intersex Plays a Role in Microbial Homeostasis in the Brown Planthopper

SIMPLE SUMMARY: RNAi-mediated knockdown of intersex in the newly emerged Nilaparvata lugens leads to abnormal expansion of the copulatory bursa by infection filled with bacteria. RNA-seq analysis shows a significant enrichment of immune defense genes responsive to bacteria in differentially expressed genes (DEGs). Moreover, inhibition of intersex expression by dsRNA treatment results in changes in the richness index of symbiotic microorganisms in copulatory bursa, fat body, and midgut of the planthopper. Specifically, significant changes are observed in the microbial community composition of the copulatory bursa. These findings reveal the function of intersex in maintaining microbial homeostasis in this insect, thereby providing insight to improve the pest control strategies. ABSTRACT: Insects harbor a wide variety of symbiotic microorganisms that are capable of regulating host health and promoting host adaptation to their environment and food sources. However, there is little knowledge concerning the mechanisms that maintain the microbial community homeostasis within insects. In this study, we found that the intersex (ix) gene played an essential role in maintaining microbial homeostasis in the brown planthopper (BPH), Nilaparvata lugens. Injection of the double-strand RNA targeting N. lugens ix (Nlix) into the newly emerged females resulted in abnormal expansion of the copulatory bursa of BPH after mating. Further observation by transmission electron microscopy (TEM) revealed that the abnormally enlarged copulatory bursa resulting from dsNlix treatment was full of microorganisms, while in contrast, the copulatory bursa of dsGFP-treated individuals stored a large number of sperm accompanied by a few bacteria. Moreover, RNA-seq analysis showed that the gene responses to bacteria were remarkably enriched in differentially expressed genes (DEGs). In addition, 16s rRNA sequencing indicated that, compared with control samples, changes in the composition of microbes presented in dsNlix-treated copulatory bursa. Together, our results revealed the immune functions of the Nlix gene in maintaining microbial homeostasis and combating infection in BPH.