Characterization,Expression and Function Analysis of DAX1 Gene of Scallop （Chlamys farreri Jones and Preston 1904） During Its Gametogenesis

DAX 1,a member of nuclear receptor superfamily,has a function in the sex determination and gonadal differentiation of several vertebrate species.However,little information about DAX1 of invertebrates is available.Here we cloned a homolog of scallop （Chlamys farreri Jones and Preston 1904） dax1,Cf-dax1,and determined its expression characteristics at mRNA and protein levels.The cDNA sequence of Cf-dax1 was 2093 bp in length,including 1404 bp open reading frame （ORF） encoding 467 amino acids.Unlike those of vertebrates,no conserved LXXLL-related motif was found in the putative DNA binding region of Cf-DAX1.Fluorescence in situ hybridization showed that Cf-dax1 located on the short arm of a pair of subtelocentric chromosomes.Tissue distribution analysis using semi-quantitative RT-PCR revealed that Cf-dax1 expressed widely in adult scallop tissues,with the highest expression level found in adductor muscle,moderate level in mantle,gill and testis,and low level in kidney,ovary and hepatopancreas.The result of quantitative real-time PCR indicated that the expression of Cf-dax1 was significantly higher （P＜0.05） in testis than in ovary at the same stage,showing a sex-dimorphic expression pattern.Furthermore,immunohistochemical detection found that Cf-DAX1 mainly located in spermatogonia and spermatocytes of testis and in oogonia and oocytes of ovary,implying that DAX1 may involve in gametogenesis of bivalves.     

Cloning and Analysis of Calmodulin Gene from Porphyra yezoensis Ueda （Bangiales, Rhodophyta）

In order to understand the mechanisms of signal transduction and anti-desiccation mechanisms of Porphyra yezoensis, cDNA and its genomic sequence of Calmodulin gene (CaM) was cloned by the technique of polymerase chain reaction (PCR) based on the analysis of P. yezoensis ESTs from dbEST database. The result shows that the full-length cDNA of CaM consists of 603 bps including an ORF encoding for 151 amino acids and a terminate codon UGA, while the length of genomic sequence is 1231 bps including 2 exons and 1 intron. The average GC content of the coding region is 58.77%, while the GC content of the third position of this gene is as high as 82.23%. Four Ca²⁺ binding sites (EF-hand) are found in this gene. The predicted molecular mass of the deduced peptide is 16688.72 Da and the pI is 4.222. By aligning with known CaM genes, the similarity of CaM gene sequence with homologous genes in Chlamydomonas incerta and Chlamydomonas reinhardtii is 72.7% and 72.2% respectively, and the similarity of the deduced amino acid sequence of CaM gene with homologous genes in C. incerta and C. reinhardtii are both 71.5%. This is the first report on CaM from a species of Rhodophyta.     

Effect of Bacillus baekryungensis YD13 Supplemented in Diets on Growth Performance and Immune Response of Sea Cucumber（Apostichopus japonicus）

The effect of a potential probiotic on the growth performance and immune response of sea cucumber（Apostichopus japonicus） was investigated. Bacillus baekryungensis YD13 isolated from sea cucumber culturing ponds was added to sea cucumber basal feed as a probiotic in different doses（0, the control; 1×10^4（YD134）, 1×10^6（YD136） and 1×10^8（YD138） CFU g-1 of diet）, and administered orally to A. japonicus（initial mean wet weight 5.44 g ± 0.17 g）. The sea cucumbers were fed in 20 aquaria, 5 each treatment, for 60 d. At the end of growth trial, 20 sea cucumbers from each treatment were challenged with Vibrio splendidus. A. japonicus in YD134 and YD136 exhibited significantly better growth performance than control（P 〈0.05）. Five non-specific immune parameters including lysozyme, acid phosphatase, alkaline phosphatase, superoxide dismutase and catalase in coelomic fluid were measured to evaluate the immune response of A. japonicus to the probiotics. Results showed that all parameters were significantly improved when YD11 was supplemented in the dose of 1×10^6 CFU g^-1（P 〈0.05）. The cumulative incidence and mortality after the Vibrio splendidus challenge decreased significantly in sea cucumbers of YD136. Accordingly, 1×10^6 CFU g^-1 of YD13 in diet was recommended for the growth promotion and immune enhancement of A. japonicus.