Insigths Into Secondary Carotenoid Synthesis in the Green Algae Haematococcus Pluvialis

Abstract

The unicellular green alga Haematococcus pluvialis accumulates secondary carotenoids in extraplastidic lipid vacuoles. The presumed sight of carotenoid synthesis are the chlorplasts which implies some form of intracelular transport to the cytoplasm. Two inhibitors of carotenoid biosynthesis, diphenylamine (DPA) and norflurazone (NF) were used to help elucidate the processes involved in this transport. The carotenoids of the lipid vacuoles and of the membranes were then analyzed by HPLC. Use of DPA resulted in the accumulation of b-carotene and an increase of the de-epoxidn. state due to enhanced zeaxanthin concns. When the DPA inhibited cells were treated with NF to prevent further carotenoid synthesis by blocking phytoene desaturase, significant conversion of the accumulated b-carotene pool to astaxanthin esters occurred. The results indicate that carotenoid biosynthetic pathway intermediates may be the transported form of carotenoids from the chloroplast and indicate that further enzymic activity occurs inside the cytoplasmic lipid vacuoles. [on SciFinder (R)]