A bacterial pathogen infecting gametophytes of Saccharina japonica (Laminariales, Phaeophyceae)

A newly identified bacterial disease of kelp(Saccharina japonica) gametophytes was found in clone cultures.It is characterized by swollen gametophyte cells in the early period of infection followed by filamentous fading.An alginolytic marine bacterium referred to as A-1 was isolated from the diseased gametophytes.On the basis of 16S rDNA sequencing and morphological,physiological and biochemical characteristics,the bacterium was identified as a strain of the genus Alteromonas.By testing Koch’s postulates,Alteromonas sp.A-1 was further confirmed as the pathogen.The infection process was also investigated using both scanning electron and light microscopy.     

Characterization of ribulose-1, 5-bisphosphate carboxylase/oxygenase and transcriptional analysis of its related genes in Saccharina japonica (Laminariales,Phaeophyta)

Saccharina japonica is a common macroalga in sublittoral communities of cold seawater environments,and consequently may have highly effi cient ribulose-1,5-bisphosphate carboxylase/oxygenase(Rubisco)activity for carbon assimilation.In our study,we cloned the full-length Rubisco gene from S.japonica(SJ-rbc).It contained an open reading frame for a large subunit gene(SJ-rbcL)of 1 467 bp,a small subunit gene(SJ-rbcS)of 420 bp,and a SJ-rbcL /S intergenic spacer of 269 bp.The deduced peptides of SJ-rbcL and SJ-rbcS were 488 and 139 amino acids with theoretical molecular weights and isoelectric points of 53.97 kDa,5.81 and 15.84 kDa,4.71,respectively.After induction with 1 mmol/L isopropyl-β-Dthiogalactopyranoside for 5 h and purifi cation by Ni 2+ affi nity chromatography,electrophoresis and western blot detection demonstrated successful expression of the 55 kDa SJ-rbcL protein.Real-time quantitative PCR showed that the mRNA levels of SJ-rbcL in gametophytes increased when transferred into normal growth conditions and exhibited diurnal variations: increased expression during the day but suppressed expression at night.This observation implied that Rubisco played a role in normal gametophytic growth and development.In juvenile sporophytes,mRNA levels of SJ-rbcL,carbonic anhydrase,Calvin-BensonBassham cycle-related enzyme,and chloroplast light-harvesting protein were remarkably increased under continuous light irradiance.Similarly,expression of these genes was up-regulated under blue light irradiance at 350 μmol/(m 2·s).Our results indicate that long-term white light and short-term blue light irradiance enhances juvenile sporophytic growth by synergistic effects of various photosynthetic elements.     

Identification of two major histocompatibility (MH) class II A genes and their association to Vibrio anguillarum infection in half-smooth tongue sole (Cynoglossus semilaevis)

Major histocompatibility complex class II antigens are important in vertebrate immune system.In the present study,the full cDNA sequence of class II A gene was synthesized by RACE-PCR from half-smooth tongue sole(Cynoglossus semilaevis),and its open reading frame(ORF) polymorphism was studied.The whole cDNA sequence was 992 bp in length,including the ORF with 717 bp.Twenty-five alleles were identified and clustered into two distinct groups according to the specific nucleotides/amino acids in specific positions.Eleven alleles belonged to Cyse-DAA while fourteen alleles belonged to Cyse-DBA.Four Cyse-DAA alleles were observed in one individual,and three to five Cyse-DBA alleles were observed in each of the three detected individuals,which indicated that at least two loci existed in each gene.Moreover,in order to study the function of the alleles in resistance to infection,200 individuals were intraperitoneally injected with Vibrio anguillarum and the first 20 dead individuals and 20 surviving ones were selected for genotype analysis.Fifty-six alleles were identified among the 40 individuals.Twenty-nine alleles belonged to Cyse-DAA and the other 27 alleles belonged to Cyse-DBA.Eighteen alleles were selected for studying their function in resistance to infection.Alleles Cyse-DAA*0201,Cyse-DAA*1101,Cyse-DBA*0401,Cyse-DBA*1102,Cyse-DBA*1801 and Cyse-DBA*2201 were identi-fied only in surviving individuals,while alleles Cyse-DAA*0901,Cyse-DBA*1101 and Cyse-DBA*1401 occurred more frequently in dead individuals.This study confirmed the existence and polymorphism of two class II A genes as well as the relationship between alleles of class II A genes and disease susceptibility/resistance in half-smooth tongue sole.     

Response to selection for fast growth in the second generation of Pacific oyster (Crassostrea gigas)

Mass selection for fast growth was conducted in three Pacific oyster (Crassostrea gigas) stocks from China, Japan and Korea using previously established lines (CS1, JS1, and KS1). To determine whether continuous progress can be achieved by selection for growth, the progeny of three second-generation Pacific oyster lines was selected for shell height and evaluated via a 400-day farming experiment. When harvested at the end of the experiment, the selected crosses of CS2, JS2, and KS2 lines grew by 9.2%, 10.2% and 9.6% larger than the control crosses, respectively. During grow-out stage, the genetic gain of three selected lines was (10.2 ± 1.4)%, (10.4 ± 0.3)%, and (8.4 ± 1.6)%, respectively; and the corresponding realized heritability was 0.457 ± 0.143, 0.312 ± 0.071 and 0.332 ± 0.009, respectively. These results indicated that the selection for fast growth achieved steady progress in the second generation of oyster. Our work provides supportive evidence for the continuity of the Pacific oyster selective breeding program.     

Application of CEDA and ASPIC computer packages to the hairtail (Trichiurus japonicus) fishery in the East China Sea

Surplus-production models are widely used in fish stock assessment and fisheries management due to their simplicity and lower data demands than age-structured models such as Virtual Population Analysis. The CEDA (catch-effort data analysis) and ASPIC (a surplus-production model incorporating covariates) computer packages are data-fitting or parameter estimation tools that have been developed to analyze catch-and-effort data using non-equilibrium surplus production models. We applied CEDA and ASPIC to the hairtail (Trichiurus japonicus) fishery in the East China Sea. Both packages produced robust results and yielded similar estimates. In CEDA, the Schaefer surplus production model with log-normal error assumption produced results close to those of ASPIC. CEDA is sensitive to the choice of initial proportion, while ASPIC is not. However, CEDA produced higher R 2 values than ASPIC.