Abstract:Based on the cloning of Exopalaemon carinicauda E75 (EcE75, GenBank accession number: KY471317), we studied its role in molting and the expression pattern of EcECR and EcRXR during different stages of molting. The full-length cDNA of EcE75 is 3944 bp long, which contains an open reading frame (ORF) of 2520 bp. The protein encoded by EcE75 is composed of 839 amino acids. The estimated mass of the deduced amino acid sequence of EcE75 is 92.307 kDa, and the calculated theoretical isoelectric point (pI) is 7.48. The ZnF_C4 and the HOLI domains were detected in EcE75, and one distinct transmembrane helix was identified. The gene EcE75 is conserved during evolution. The phylogenetic tree constructed based on E75 sequences showed that EcE75 was clustered with that of the same clade of crustaceans. E. carinicauda has the highest homology with Fenneropenaeus chinensis, Portunus trituberculatus, Litopenaeus vannamei, and Gecarcinus lateralis. The tissue distribution analysis showed that EcE75 transcript could be detected in all tested tissues of E. carinicauda, and relatively abundant in eyestalk and ovary. The expression pattern of the genes EcRXR, EcECR, and EcE75 was consistent during different stages of molting. At the premoult and postmoult stages, the expression of genes of reproductive molting was significantly higher than that of growth molting. The results showed that there was significant difference between the growth and reproductive molting because of the ovary development. Furthermore, it revealed the effect of ecdysone stimulation on ovarian development through the upregulation of expression of the genes EcRXR, EcECR, and EcE75. The present study on the expression of the genes EcRXR, EcECR, and EcE75 at different stages of molting provides a theoretical basis and a scientific ground for further research on the mechanism of molting.
