Screening And Analysis Of Growth Decline Related Genes From Alexandrium Catenella (Dinofagellate)

With the woldwide industrialization, red tide events were reported more frequently and their harm to people had become more and more severe. Though, great efforts had been made to elucidate the ecology and biology of red tide, the studies of the molecular biological mechanism of red tide blooming were still limited, including that involved in the declining of red tide. Suppression subtractive hybridization (SSH) technology was used to construct a growth decline specific cDNA library of Alexandrium catenella. A total of 800 clones were obtained from the SSH library, and 556 positive clones were identified by nested PCR. Dot blot hybridization was performed to screen differential expressed genes from the positive clones. Ultimately, we got 160 differential expressed clones. After sequencing and classification, 21 sequences were obtained from which 6 were found homologous with functional genes in NCBI. These functional genes were matched with CHK1 checkpoint-like protein, Exosomal 3'-5' exoribonuclease complex, glutaredoxin, Na~+/ K~+ ATPase, ORF44l (chloroplast) and pG1 protein, respectively. Others had no hit by blast searching, and were predicted to be novel. We speculate that the growth decline of A.catenella involves DNA damage, mRNA degradation, redox status changes, ion dynamic equilibrium processes and some changes of chloroplast physiological status. The result of real-time PCR for validating the pG1 protein which had a high frequency indicated that its expression in decline phase is higher than other phases. Partial sequences of actin gene in Alexandrium catenella were cloned. After sequencing , a fragement of 110bp was obtained. For the purpose of studying the evolution of conservation genes , alignments of homologous genes of actin and cob were done between Alexandrium catenella and other dinoflagellates, and phylogram trees based on these two genes were constructed. Phylogram trees were different between that built based on actin and cob gene, which suggested the possibility that the different evolutional ways between these two genes.The phylogram tree based on actin indicated that the evolution of this gene is conformity with evolution position of species. But that based on cob indicated that the evolution of this gene is not conformity with evolution position of species.