Abstract: Protein ubiquitination is a fundamental post-translational modification event that serves as a signaling function in diverse biological processes,including cell-cycle progression,cell apoptosis,gene transcriptional regulation and expression,etc. In these processes of ubiquitin-proteasome pathway,ubiquitin-conjugating enzyme E2 is of pivotal importance that mediates more than 80 percent of protein degradation of eukaryotic cells,and it plays a key role on the specific selection of degraded of target protein. In this study,a homologous gene fragment of ubiquitin-conjugating enzymes E2 D4（Lc-UBE2D4）was screened from previous constructed normalized gonad cDNA library of large yellow croaker Larimichthys crocea was obtained,and its full length cDNA was cloned by using SMART-RACE technology,and then the differential expression profiles in different tissues and different gonadal development stages were analyzed using quantitative real time PCR（qRT-PCR）. The full length cDNA of Lc-UBE2D4 gene was of 798 bp,with 441 bp of ORF encoding a protein of 147 amino acids,and it contained the highly conserved ubiquitin-conjugating enzymes UBC domain and an active site cysteine. The qRT-PCR results revealed that the highest expression level of Lc-UBE2D4 presented in spleen and testis which were extremely higher than those in other tissues（P < 0.01）,and its expression level in ovary was significantly higher than other organs（excluding spleen and testis）（P < 0.05）. Moreover,its expression levels in three stages of testis were higher than in the same growth stages of ovary（P < 0.05）. These results suggested that Lc-UBE2D4 played essential roles in the gonad development,especially in testis development. Meanwhile,Lc-UBE2D4 may be involved in immune function due to highest expression in spleen.

Key words: ubiquitination, Lc-UBE2D4, large yellow croaker, tissue expression, gonad development