beta-carotene is the intermediate exported from the chloroplast during accumulation of secondary carotenoids in Haematococcus pluvialis

Recent findings on the localization in Haematococcus pluvialis of an early and a late enzyme in astaxanthin synthesis have suggested the sequential in volvement of two compartments, the chloroplast (site of early synthesis) an d the cytoplasmic lipid vesicles. Here the intermediate transported across the chloroplast envelope into the cytoplasm is elucidated by means of the i nhibitors diphenylamine (DPA) and 2-(4-chlorophenylthio)-triethylamine (CPT A). Based on the amounts of the intermediates accumulated upon inhibitor tr eatment and their occurrence in the lipid vesicle fractions, it is conclude d that the transport takes place after beta -ionone ring cyclization. A non -vesicle mechanism of beta -ionone carotenoid transport from the chloroplas t towards the cytoplasmic lipid vesicles via carotenoid binding proteins is suggested.