Krüppel Homolog 1 Is Required for the Role of Methyl Farnesoate in Vitellogenesis in the Mud Crab Scylla paramamosain

Methyl farnesoate (MF), a counterpart of insect juvenile hormones in crustaceans, plays essential roles in molting, metamorphosis, and reproduction. In this paper, we isolated a gene-encoding Krüppel homolog 1 from the mud crab Scylla paramamosain (Sp-Kr-h1) and investigated its involvement in MF-regulated vitellogenesis. RT-PCR showed that Sp-Kr-h1 had a wide expression in various tissues. qRT-PCR showed that its expression level in the ovary peaked at stage III. Both in vitro and in vivo experiments suggested that the expression of Sp-Kr-h1 and Vitellogenin (Vg) in the hepatopancreas was significantly induced by MF administration. Further, the RNA interference technique was employed to illustrate the precise role of Sp-Kr-h1 in ovarian development. This revealed that the in vitro silencing of Sp-Kr-h1 significantly decreased the level of Vg transcripts located in the hepatopancreas. Meanwhile, an in vivo experiment demonstrated that oocyte growth was inhibited after the knockdown of Sp-Kr-h1 in female S. paramamosain. In conclusion, this study identified a Kr-h1 gene in S. paramamosain and demonstrated that it is an essential factor for MF-regulated vitellogenesis. Our results provided a new insight into the mechanism underlying MF inducing ovarian development in mud crabs.