Abstract: Nm23 is a family of genes encoding the nucleoside diphosphate（NDP）kinase，which functions in a wide variety of biological processes，including growth，development，differentiation，and tumor metastasis. In this study，based on the nm23 homologous sequence in the transcriptome dataset of Portunus trituberculatus，the full-length cDNA of P. trituberculatus nm23 was obtained using the rapid amplification of cDNA ends（RACE）. The full-length cDNA（GenBank accession number KP027331）was 777 bp，encoding for a protein of 151 amino acids with one typical NDP kinase domain that harbored all the crucial residues for nucleotide binding and enzymatic activity. The deduced amino acid sequence of P. trituberculatus nm23 exhibited more than 90% identities with that of other crustaceans，and more than 70% identities with the nm23 of group I of vertebrates. The phylogenic tree constructed based on nm23’s amino acid sequences indicated that the crustacean nm23 belonged to the group I（nm23-1），which was separated from the nm23 of group II（nm23-2），moreover，the nm23-1 and nm23-2 were close. The expression levels of P. trituberculatus nm23 in different tissues and during the ovarian development were detected by quantitative real-time PCR（qPCR）. The results showed that nm23 was ubiquitously expressed in all tissues examined，its mRNA level was the most abundant in eyestalk，muscle and Y-organs，and second in ovary and hepatopancreas. During the ovarian development，the nm23 was mostly expressed at stage I，then declined along with the development of ovaries，and to the minimum at stage V，suggesting that the nm23 had the potential role in the ovarian development of P. trituberculatus.

Key words: Portunus trituberculatus, nm23, gene cloning, ovarian development, gene expression