T7-Synthesized Double-Stranded RNA Mimicking miR-71 Induces Termite RNAi and Increases Fungal Efficacy

miR-71 has been determined to enhance the efficacy of biological control agents against termites. However, it is not clear how miR-71 functions in enhancing the termite control. In this study, we tested the effects of termite miR-71 on the transcriptional and translational profiles of termites via the commercial product miR-71 agomir, and meanwhile developed a cost-effective method using T7 RNA polymerase to synthesize a miR-71 mimic, comparing the effects of the T7-synthesized miR-71 mimic versus the commercial miR-71 agomir on the gene expressions and infection mortality of termites. Comparative bioassays demonstrated that both miR-71 mimic and agomir significantly increased fungus-induced termite mortality with equivalent bioactivity. Mechanistically, transcriptomic and proteomic analyses revealed that commercial miR-71 agomir modulated the expression of defense-related genes, such as <i>hexamerin-1</i>, <i>neuroligin-4</i>, and <i>probable chitinase</i>-10. Meanwhile, RT-qPCR confirmed that T7-synthesized miR-71 mimic induced similar expression changes in the same target genes. Additionally, the dsRNA-mediated silencing of <i>hexamerin-1</i>, <i>neuroligin-4</i>, and <i>probable chitinase</i>-10 made termites more vulnerable to the fungus, respectively. Our study establishes in vitro-transcribed miRNA mimics as potent and cost-effective tools for studying 'miRNA-mRNA' interaction, and meanwhile lays the foundation for the microbe-mediated expression of small-RNA mimics in enhancing termite biocontrol.