A novel microRNA and its PFK target control growth length in the freshwater shrimp (Neocaridina heteropoda)

Abstract

MicroRNAs (miRNAs) are small non-coding RNAs that negatively regulate gene expression and play roles in a wide range of physiological processes, including ontogenesis. Herein, we discovered a novel microRNA, novel miR-26, which inhibits translation of the phosphofructokinase (PFK) gene by targeting the 3’ untranslated region (UTR) of pfk directly, thereby inhibiting the molting and body length growth of the freshwater shrimp (Neocaridina heteropoda). Lowering expression of the PFK gene by RNA interference (RNAi) led to a longer ecdysis cycle and smaller individuals. This phenotype was mirrored in shrimps injected with novel miR-26 agomirs, but the opposite phenotype occurred in shrimps injected with novel miR-26 antagomirs (i.e., the ecdysis cycle was shortened and body length was increased). After injection of 20-hydroxyecdysone (ecdysone 20E), expression of the novel miR-26 was decreased, while expression of the PFK gene was up-regulated, and the fructose-1,6-diphosphate metabolite of PFK accumulated correspondingly. Furthermore, expression of eIF2 (eukaryotic initiation factor 2) increased under stimulation of fructose-1,6-diphosphate, suggesting that protein synthesis was stimulated during this period. Taken together, our results suggest that the novel miR-26 regulates expression of the PFK gene and thereby mediates the molting and growth of N. heteropoda.