Abstract: Small RNA (sRNA) is a class of non-coding RNA with the sequence length shorter than 300 bp. It plays important roles in regulation of cell growth, division, differentiation, proliferation and apoptosis. A number of studies in recent years have found the interspecific transmission of sRNAs and their regulatory roles as signaling molecules in a cross-kingdom manner. In addition to visual and chemical information, organisms can also communicate via various molecular signals. sRNA can serve as a molecule signal linking animals, plants, and microorganisms, for its mobility and regulatory role in gene expression, not only within organism, but also across species. Insects, with the largest number of species and occupying the most abundant niches on earth, have been found owing a variety of exogenous sRNA molecules inside their bodies. In the article, we analyzed the molecular basis that sRNA mediates the cross-kingdom regulation, summarized the recent research progress on cross-kingdom sRNAs, which enter insect bodies through biological interaction, regulate gene expression in insects, and affect interactions of insects with their host plants and pathogenic microorganisms. We also discussed the influences of sRNA-mediated cross-kingdom RNAi on the ecological adaptability of insects and their prospective application in pest control. Cross-kingdom transfer of sRNA molecules between insects and plants can regulate plant resistance to insect pests and caste differentiation of social insects. Cross-kingdom regulation of sRNA from microorganisms can assist the invasion of pathogenic microorganisms in insects or affect the development of parasitic wasps. Based on genetic engineering, cross-kingdom regulation with modified or artificially expressed exogenous sRNA would be a new approach for development of efficient biological control products for insect pest control.-

Key words: Insects, molecular signals, small RNA, cross-kingdom regulation, biological interaction, pest control