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Recently, “Synergistic action of the gut microbiota in environmental RNA interference in a leaf beetle” was published in Microbiome (IF₅: 12.16), the top journal of microbial ecology, by the research team of Prof. Zhang Jiang from the State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University. Associate Professor Xu Letian and Doctoral Postgraduate Xu Shijing are the first co-authors of this paper, Professor Zhang Jiang is the communication author, and Hubei University is the first unit.

Plant diseases and pests result in huge economic losses of agricultural production. Traditional chemical pesticides still play an important role in the prevention and control of crop pests, while abuse of chemical pesticides poses a threat to the environment and human health. Therefore, the current dilemma calls for efficient and environmentally friendly biological pesticides. RNA interference ( RNAi ) is a conserved double-stranded RNA ( dsRNA ) -induced gene silencing in eukaryotes, and won the Nobel Prize in Physiology or Medicine in 2006. The mechanism of RNAi-based pest control achieves its aim by interfering with the key genes that control the development or important behavior of pests, and inhibiting the growth and reproduction of pest insects, and even directly results in its death. Double-stranded RNA, the main component of RNAi, is ubiquitous in organisms and easy to be degraded in the environment. Therefore, it is nontoxic and non-residual. It is a new green pest control method and shows broad application prospects.

When insects ingest dsRNA molecules, the molecules must pass through the insect’s gut and target against essential genes of pests, thus accelerating its death. During this process, dsRNA inevitably contacts with gut bacteria. Although previous studies have reported many functions of gut bacteria of insects, it is still unknown that whether gut bacteria interact with dsRNA molecules and how the gut microbiota affects RNAi responses in insects.

Professor Zhang Jiang ' s team used willow leaf beetle, Plagiodera versicolora, as the research object to explore problems mentioned above. They compared the RNAi efficiency of sterile insects and bacterial insects, and found that gut bacteria enhanced the insecticidal efficiency of RNAi, but did not affect the down-regulation level of target genes. In order to further explore its mechanism, the researchers used microbial flora, fluorescence quantitative PCR, bacterial isolation and identification, microinjection and other technical means to clarify the mechanism : on the one hand, after dsRNA molecules were ingested by the beetle, the dsRNA enzyme in the gut of the beetle would degrade it into ribose and other substances, these degradation products as nutrients, selectively promoted the growth of Pseudomonasputida and other bacteria, resulting in flora disorder. Then the bacteria broke through the gut barrier, invaded the blood cavity of the pest and killed the beetle. On the other hand, RNAi down-regulated the pest genes, resulting in reduced immunity of pests and being unable to effectively control the flora disorder (Fig.1). This study found a new pesticide mechanism of RNAi, and enriched people’s understanding of gut bacterial function, which has important theoretical and application value.

Figure 1. Death of Willow Leaf Beetle Resulted by Synergistic Action of the Gut Microbiota in Environmental RNAi  

Professor Zhang Jiang 's team has long been engaged in the basic theory and application research of advanced biotechnology in plastid engineering and plant protection, and has achieved important innovations in the mechanism and technology of plastid-mediated RNAi in recent years. The main achievements include: the creation of a new strategy of plastid-mediated RNAi insect resistance, the discovery of dsRNA enzyme’s being the key factor to affect the response of insect pests to RNAi, the development of a plant efficient broad-spectrum antiviral technology based on programmable enzymes, and the discovery of intestinal bacteria’s ability of accelerating the lethality of RNAi to pests. More than 30 papers were published in internationally renowned authoritative journals such as Science, Trends in Biotechnology, Microbiome, Plant Biotechnology Journal, Journal of Experimental Botany, and Pest Management Science. And their projects are supported by key research and development projects, national natural science fund general projects, and natural science fund innovation groups in Hubei Province.

Link to the article: https://doi.org/10.1186/s40168-021-01066-1