Expression of the cyclin-dependent kinase 2 gene (cdk2) influences ovarian development in the ridgetail white prawn, Exopalaemon carinicauda

Synchronization of ovary development is the premise for realizing large-scale seed breeding of small- and medium-sized shrimps. To explore the genetic mechanism that determines ovarian development in the ridgetail white prawn Exopalaemon carinicauda, we successfully cloned the full-length cDNA sequence of the cdk2 gene of E. carinicauda. The open reading frame (ORF) of cdk2 is 918 bp, which encodes 305 amino acids with a conserved cyclin binding motif S_TKc. The phylogenetic analysis showed that cdk2 has the highest homology with the cdk2 of the decapods, Macrobrachium japonicus and M. rosenbergii, which are clustered together. The results of qRT-PCR showed that the expression of cdk2 gradually increased in embryos from fertilized eggs, reaching the highest level in the anterior nodal larvae. The expression level of cdk2 decreased significantly after the anterior nodal larva stage (P < 0.05). Cdk2 was expressed in nine tissues (eye stalk, stomach, heart, gill, intestine, muscle, ovary, hepatopancreas, and ventral cord), with the highest expression in the ovary, at a level that was significantly different from the other tissues (P < 0.05). In the ovary, the expression level of this gene was highest in developmental stage Ⅲ and lowest in stage Ⅱ, which was significantly different from the other stages (P < 0.05). RNAi results showed that reducing the cdk2 expression level could significantly delay ovarian development. The results of in situ hybridization further revealed that cdk2 plays an important role in the proliferation of oocytes, and the synthesis and transportation of exogenous yolk material.