Synergistic action of the gut microbiota in environmental RNA interference in a leaf beetle

利用无菌昆虫及RNAi，发现肠道细菌增强了RNAi的杀虫效率，却并没有影响靶标基因的下调水平。为进一步探明其机制，研究人员利用微生物组、荧光定量PCR、细菌分离鉴定、显微注射等技术手段，明确了其中机制：一方面，dsRNA分子被柳蓝叶甲取食后，叶甲肠道内的dsRNA酶会将其降解成核糖等物质，这些降解产物作为营养物质，选择性的促进了Pseudomonas putida等细菌的生长，导致菌群紊乱，随后细菌突破肠道屏障，侵入害虫血腔，杀死叶甲；另一方面，RNAi下调了害虫的基因，导致害虫免疫力降低，无法有效控制菌群紊乱。该研究发现了RNAi杀虫新机制，并丰富了人们对肠道细菌功能的认识，具有重要的理论和应用价值。

By utilizing germ-free insects and RNAi, researchers found that gut bacteria enhance the insecticidal efficacy of RNAi without affecting the downregulation level of target genes. To further elucidate the underlying mechanism, the research team employed multiple technical approaches including microbiome profiling, quantitative real-time PCR (qPCR), bacterial isolation and identification, and microinjection to clarify the specific regulatory mechanism: On one hand, following the ingestion of dsRNA molecules by *Plagiodera versicolora*, dsRNases present in the beetle's gut degrade dsRNA into substances such as ribose. These degradation products serve as nutrients, selectively promoting the growth of bacteria including *Pseudomonas putida*, thereby inducing gut microbiota dysbiosis. Subsequently, the bacteria breach the intestinal barrier and invade the pest's hemocoel, ultimately killing the beetle. On the other hand, RNAi-mediated downregulation of the pest's genes impairs the pest's immune system, rendering it incapable of effectively regulating the microbiota dysbiosis. This study identifies a novel insecticidal mechanism of RNAi, expands the current understanding of gut bacterial functions, and possesses significant theoretical and applied research value.