Cyanobacteria And Green Algae Carotene Synthase Gene Of Comparative Genomics And The Metabolic Regulation Of Research

Caroteniods have many important physiological functions in organisms. Especially, astaxanthin has a high antioxidant activity, an anti-cancer activity, and other biological activities. This paper aims at the comparative genomics of the cyanobacterial carotenoid biosynthetic pathway. In addition, psy and pds were cloned and regulatory sequences were isolated and characterized in Haematococcus pluvialis. And also, expression patterns of crt gene were studied from Haematococcus pluvialis.Genome-wide screening of crt genes based on the genome-sequencing project provided us a new and comprehensive insight into the cyanobacterial carotenoid biosynthetic pathway. It is interesting to find that nearly all the cyanobacteria share quite similar pathway to synthesizeβ-carotene except for Gloeobacter violaceus PCC 7421 which is bacterial-type. The enzymes involved in the upstream pathway are more conserved than the subsequent ones. In addition, many carotenoid synthesis enzymes exhibit diversity in structure and function.Results of comparative genomics show there was not only no detectable crtL-e- but also no crtL-b-like lycopene cyclase gene in the genomes of Synechocystis sp. PCC6803 et al. However, there are homologous genes (sll0147 and sll0659,et al.) to a new type lycopene cyclase cruA from C. tepidum in these species. By genetical transformation system of Synechocystis sp.PCC6803, sll0147 and sll0659 which are similar to cruA were characterized. Full segregants of the sll0147 deletion in Synechocystis were not obtained, implying that this gene is essential for survival. The results of HPLC reveal these two enzymes have no lycopene cyclase activtity. However, the transmission electron micrographs showed that one major effect of the deletion is the abnormal phenotype, which suggests that sll0659 affects the cell division directly or indirectly.Phytoene synthease gene (psy) and phytoene desaturase gene (pds) were cloned from H. pluvialis. In addition, their 5'-flanking upstream sequences are obtained using adaptor-primer PCR method. The transient expressions of lacZ driven by psy 297bp and pds 210bp 5'-flanking sequence show that these sequences contain transcription regulatory sequences.In order to study the expression regulation, H.pluvialis was reduced by ABA, N starvation and high light. The expression patterns of crt genes were analysis by semi RT-PCR. The results showed all of genes were up-regulated except for lcy.This is the first report on the comparative genomics of carotenoid synthetic pathway of cyanobacteria and isolation of genomic genes and 5'flanking regions of psy and pds from H. pluvialis. This research provides a foundation for further study to finding new crt gene and the metabolic regulation of carotnoids.