Cloning, Expression Pattern Of Ubiquitin Fusion Protein Genes In Chinese Mitten Crab (Eriocheir Sinensis)

The ubiquitin/proteasome pathway plays an important role in gametogenesis. Ubiquitin/ribosomal fusion protein is the precursor of mono-ubiquitin and is highly expressed in active cells. We identified two ubiquitin/ribosomal fusion proteins in the testis, accessory gonad and ovary of Eriocheir sinensis. The ubiquitin-ribosomal proteins S27and L40are denoted as UbS27and UbL40, respectively. The full length Es-UbS27cDNA (565bp) was cloned using PCR, based upon an initial expressed sequence tag (EST) isolated from a testicular cDNA library and the result of3'RACE. The sequence contained a465-nucleotide open reading frame (ORF) that encoded a protein of154amino acids, with a predicted molecular mass of17.8kDa. It contained a Ubiquitin (Ub) domain and the ribosomal protein S27. The full-length Es-UbL40cDNA (521bp) contained a390-nucleotide open reading frame (ORF) that encoded a protein of129amino acids, with a predicted molecular mass of14.7kDa. It contained a Ub domain and the ribosomal protein L40. By Real-time PCR, the expression level of these two Ub genes is shown to change significantly in the developing testis and ovary, reaching peak expression in August and October, respectively. During accessory gonad seasonal development, the expression of UbS27and UbL40varied sharply and reached peak expression in November. The results of in situ hybridization of testis and ovary, indicated that Ub transcription takes place widely. Our study demonstrates, for the first time, that Es-UbS27and Es-UbL40play key roles in gametogenesis and reproductive success of the Chinese mitten crab.