Compartmentation of astaxanthin biosynthesis in Haematococcus pluvialis

Abstract

Under stress, the unicellular green alga Haematococcus pluvialis accumulates secondary carotenoids, mainly astaxanthin esters, in cytoplasmic lipid vesicles up to 4 % of its dry mass. It is therefore one of the favored organisms for the biotechnological production of these antioxidative compounds. We have studied the cellular localization and regulation of several enzymes leading to the ketocarotenoid astaxanthin using RT-PCR, immunogold labeling of ultrathin sections and Western blot analysis of cell fractions. From the results, a transport of intermediates from the site of early biosynthetic steps in the chloroplast to the site of oxygenation and accumulation in cytoplasmic lipid vesicles is proposed.