Expression of genes that encode astaxanthin biosynthetic enzyme under various stress conditions

Abstract

Upon environmental stress such as strong irradiance or nitrogen deficiency unicellular green algae of the genus Haematococcus accumulate ketocarotenoid astaxanthin in the cytosol. To induce astaxanthin content of H. pluvialis, immature cells were incubated in NaNO3 free MBBM at 25℃ under continuous light intensity (900 μEㆍm-2ㆍs-1) to the column surface for 1 day. H. pluvialis cells were also incubated with methyl viologen (MV). MV interferes with the photosystem by disrupting electron transport and catalyzing the production of active oxygen within the chloroplast and produces hydroxyl radicals through either a superoxide-driven Fenton reaction or a Fenton-like reaction, which has potent toxicity. We monitored the expression of genes that encode enzymes for the biosynthesis of astaxanthin, such as phytoene synthase, carotenoid hydroxylase, phytoene desaturase, beta-carotene C-4 oxygenase. IPP isomerase, beta-carotene ketolase under these various stress condition. In addition, we also investigated the changes in carotenoids including astaxanthin under these stress conditions by using HPLC and monitored photosynthetic parameter as well. Results of this study will be discussed.