MicroRNA miR-927 targets the juvenile hormone primary response geneKruppel homolog1to controlDrosophiladevelopmental growth

Kruppel homolog1 (Kr-h1) is a juvenile hormone (JH) response transcriptional factor that transduces JH signalling to repress insect metamorphosis in both hemimetabolous and holometabolous insects. While few studies about microRNAs (miRNAs) downregulatingKr-h1expression to mediate insect metamorphosis have been demonstrated in hemimetabolous insects, the miRNAs that target theKr-h1of holometabolous insects have not been reported. Here, we identified two miR-927 binding sites within the 3 ' UTR region ofKr-h1inDrosophila melanogaster, and miR-927 was found to downregulate the expression ofKr-h1. The expression profiles of miR-927 andKr-h1displayed relatively opposite pattern during most of the larval development stages. Overexpression of miR-927 in the fat body significantly decreased the expression ofKr-h1and resulted in reduced oviposition, increased mortality, delayed pupation, and reduced pupal size. Notably, the co-overexpression ofKr-h1rescued the developmental and growth defects associated with miR-927 overexpression, indicating thatKr-h1is a biologically relevant target of miR-927. Moreover, the expression of miR-927 was found to be repressed by JH and its receptor Met/gce, forming a positive regulatory loop of JH signalling. Overall, our studies support a conserved role for the JH/miRNA/Kr-h1regulatory axis in growth control during insect development.