Analysis Of Gene Expression Of Photosynthetic Carbon Assimilation Pathway In Porphyra Yezoensis

Porphyra is a red algae genus and of great value on economic and theory research. In the special type of life history of porphyra, the sporophyte is microscopic phase while the gametophyte is the macro dominant phase, which is different from the sporophyte dominant life history in most of the higher plants. And both the gametophytes and the sporophytes of algae can photosynthesize and survive independently as autotrophic organisms. The macro phase gametophyte has a larger biomass than sporophyte, which displayed that the ability of photosynthetic carbon assimilation of gametophyte is greater than that of sporophyte. As a result, it is of great significance to have research on the related genes in carbon assimilation.Rubisco (ribulose-1, 5-bisphosphate carboxylase/oxygenase), a key enzyme of photosynthetic CO2 fixation, is also the rate-limiting enzyme in Calvin cycle. As a result, on the basis of Porphyra, systematic comparative study on the differenticial expression of Rubisco was carried out between gametophytes and sporophytes on the levels of transcription, translation and enzymic activity. Results indicated that the content and activity of Rubisco in haploid gametophyte were notably higher than that in diploid sporophyte. In order to verify the relationship of the expression level of Rubisco and the ploidy, the same comparative studies on the expression of Rubisco between gametophyte and sporophyte were carried out in Bangia fuscopurpurea and Laminaria japonica, which have representative life history in marine macroalgae. Results indicated that both content and activity of Rubisco were higher in algal gametophytes than in the sporophytes, which suggested that for the four algal species, the Rubisco content and the initial carboxylase activity were related to the ploidy of the generations rather than the accumulation of biomass.In rhodophyte (Porphyra et al.), unlike the land higher plants, the location of the Rubisco gene is different, that both the large subunit and small subunit of Rubisco are encoded in chloroplast genome, while a Rubisco spacer region with high variety exists, which is important for identification of red algae. In this study, Rubisco spacer region was applied in the identification of nine sprcies of Porphyra, and an improved method of PCR in which the small segment of conchocelis is amplified directly without DNA extraction was developed in rapid species identification, which is of great fundamental significance.Besides the research on the Rubisco expression in different generations of Porphyra, comparative studies on the genes related to carbon assimilation—containing PGK, GAPDH, TPI, FBPase, GPI, TKL and SBPase—were carried out for different generations of P. yezoensis on the level of gene expression using real-time PCR. Results indicated that the related genes expression level were higher in gametophyte than that in sporophyte.All the studies suggest that, the related expression level of genes in Calvin cycle (Rubisco et al.) were notablely higher in gametophyte than in sporophyte, which suggested that the expression the these genes were related to the ploidy of different generations of Porphyra, and this relationship maybe also exists in the other marine macroalgae with representative life history.