MicroRNA miR ‐927 targets the juvenile hormone primary response gene Krüppel homolog1 to control Drosophila developmental growth

Abstract Krüppel 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) downregulating Kr‐h1 expression to mediate insect metamorphosis have been demonstrated in hemimetabolous insects, the miRNAs that target the Kr‐h1 of holometabolous insects have not been reported. Here, we identified two miR‐927 binding sites within the 3′UTR region of Kr‐h1 in Drosophila melanogaster , and miR‐927 was found to downregulate the expression of Kr‐h1 . The expression profiles of miR‐927 and Kr‐h1 displayed relatively opposite pattern during most of the larval development stages. Overexpression of miR‐927 in the fat body significantly decreased the expression of Kr‐h1 and resulted in reduced oviposition, increased mortality, delayed pupation, and reduced pupal size. Notably, the co‐overexpression of Kr‐h1 rescued the developmental and growth defects associated with miR‐927 overexpression, indicating that Kr‐h1 is 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‐h1 regulatory axis in growth control during insect development.