ABSTRACT
To investigate the genetic structure of the purplish Washington clam population, Saxidomus purpuratus Sowerby, in Korea. A portion of mitochondrial COI gene sequences (605 bp) for phylogenetic comparison was determined. Sequence analysis of 62 individuals collected from six regions revealed 13 haplotypes. Phylogenetic analysis using Phylogeny Inference Package (PHYLIP) subdivided the purplish Washington clam into two clades (termed clade A and B), weak supported groups (<65 of bootstrap value). This haplotype subdivision was also in accordance with geographic separation; one each at Masan, Yeosu, Samcheonpo, Jubyeon and Geojedo, and the other at Sineju. Population genetic analysis subdivided these two population groups with a geographic distance (d=0.431, p=0.379). Furthermore, in the Sineju population, the maximum sequence divergence (2.67%) and minimum nucleotide diversity (0.0012426) were shown in which might be reflective of a relatively small population size and the geographical isolation of the population as compared with other populations. However, a very high migration rate (Nm=59.62-infinite) and a very low level of geographic distance (FST=-0.076-0.055) were noted to exist among the South and East Sea populations, suggesting that individuals between populations should show a significantly active genetic mixing and migration regardless of geography. These findings allowed us to conclude that the purplish Washington clam populations occurring in the South and East Sea were formed with randomly dispersed individuals.
ABSTRACT
The cDNA of Crassostrea gigas HSP70 was cloned and rapid amplification of cDNA (RACE) techniques were used. The full length of HSP70 cDNA was 2045 bp, consisting of a 5’ terminal untranslated region (UTR) of 80 bp, a 3’ terminal UTR 146 bp, and an open reading frame (ORF) of 1829 bp encoding deduced 620 amino acids. The HSP70 cDNA contained HSP70 family signatures, ATP-GTP binding site motif, tetrapeptide (GGMP) and conserved carboxyl terminal region (EEVD) at C-terminal of deduced amino acid sequence. BLAST analysis revealed that the HSP70 gene has an extreme similarity of 98.9% with C. gigas (AF144646). Northern blotting was used to examine the expression of HSP70 mRNA in the gill tissue of the oyster obtained from surface, middle and bottom layers. The HSP70 mRNA observed the samples taken from middle and bottom layers in September and February, but samples from the surface layer did not find a signal intensity of HSP70 mRNA transcript. Consequently, it seems that the oyster occurring middle and bottom layer have been stressed during the period of summer and winter, which is associated with the massive mortality in Gamak bay.