| Various stresses faced by the organisms during their lifespan cause direct damage to vital proteins leading to the impairment of cellular processes. Damage to cells as a result of stress can involve one of the two opposing responses:apoptosis, a form of cell death that removes damaged cells to prevent inflammation or stress response that prevents damage and facilitates recovery to maintain cell survival.Heat shock protein 90 (HSP90) is a highly conserved molecular chaperone that plays key role in the folding, maintenance of structural integrity and regulation of a subset of cytosolic proteins.Studies have shown that multiple stress factors transiently increase production of HSPs as protection against harmful insults.Their highly conserved structure suggests that they play roles in fundamental cellular processes. Moreover it has been proved that there are several plausible links between heat shock proteins and the immune system in organisms that are faced with bacterial challenges.In order to investigate the HSP90's effect of the oyster (Crassostrea hongkongensis) against various stress factors. In this study, full-length HSP90 cDNA was isolated from C. hongkongensis by rapid amplification of cDNA end (RACE) techniques and found to contain 2425 nucleotides, including an open reading frame, and was predicted to encode a protein of 716 amino acids. BLAST analysis indicated that the HSP90 gene of C. hongkongensis shared high homology with known HSP90 genes of other mollusks.Semi-quantitative RT-PCR was used to analyse tissues distribution of HSP90 mRNA expression in unstressed C. hongkongensis. Analysis about tissues distribution of HSP90 mRNA indicated that HSP90 transcriptional expression levels were detectible in all tissues (gill,muscle,digestive gland mantle,and heart),but highest expression in digestive gland and lowest in muscle.Fluorescent real-time quantitative PCR was employed to examine the expression pattern of HSP90 mRNA in muscle, digestive gland, gill, heart and mantle of C. hongkongensis challenged by thermal stress, pollutant(malachite green)and bacteria (Vibrio alginolyticus), respectively.All of 3 stresses could induce HSP90 expression. Moreover,expression change of HSP90 gene was a clear time-dependent expression pattern during experimental period. For thermal stress, expression of HSP90 were up-regulated in all of 5 tissues.At the earliest, the maximal expression levels appeared in gills for 3 hours,but in heart,peak of the expression appeared latest,for 24 hours. In MG treatment group, HSP90 mRNA expression in mantle and digestive gland was up-regulated gradually at first. and peaked at 4 days and 1 day. then gradually decreased to the control level at 12 days and 2 days, respectively, when the oysters were treated in MG solution (1μg/L). The phenomenon was defined as time-dependent expression pattern of HSP90 gene. However, the HSP90 mRNA levels in muscle and gills were significantly increased on day 8 and 12, respectively, but both of them did not drop to the control level during the period of MG exposure. In bacterial challenged groups, the relative expression level of HSP90 transcript was also up-regulated obviously and in gills, digestive gland, heart, the expression could rapidly reached maximal level at 3 h after injection, then dropped progressively to the original level at about 24 h post challenge.The results indicated that HSP90s was potentially involved in responses to various stress in oyster C. hongkongensis,and may play an important role in cellular stress protection.
|
PDF Full Text Request