Identification and expression pattern of the sex determination gene fruitless-like in Cherax quadricarinatus

The fruitless ( fru ) gene has an important function in the courtship behavior and sex determination pathway of Drosophila melanogaster ; however, the fru gene has never been reported in shrimps. In this study, the fruitless-like gene was identified in Cherax quadricarinatus ( Cqfru ) and is reported here for the first time. A sequence analysis revealed a conserved BTB domain in Cqfru which is the same as fru in D. melanogaster . An analysis of the expression level of Cqfru showed that it was highly expressed in the gastrula stage during embryonic development. Furthermore, in situ hybridization and expression distribution in tissues showed that its sexually dimorphic expression may be focused on the hepatopancreas, brains, and gonads. The gonads, brains, and hepatopancreas of males had a higher expression level of Cqfru than those of females; however, the expression level of the abdominal ganglion was found to be higher in females than in males in this study. The results of an RNA interference treatment showed that a knockdown of Cqfru reduced the expression of the insulin-like androgenic gland hormone (IAG) and tumor necrosis factor (TNF). The characteristic fru gene in shrimps is reported here for the first time, with the results providing basic information for research into the sex-determination mechanism in C. quadricarinatus . • The fru gene of C. quadricarinatus was identified for the first time. • The expression level of Cqfru was more highly expressed in testis than in ovaries. • Cqfru gene may directly or indirectly regulate the expression of Cq-IAG and Cq-TNF . • Cqfru participates in the process of sex determination and differentiation in C. quadricarinatus . • Cqfru may participate in the development of aggressive behavior in the male crayfish by directly or indirectly.