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

Abstract

Recent findings on the localization in Haematococcus pluvialis of anearly and a late enzyme in astaxanthin synthesis have suggested thesequential involvement of two compartments, the chloroplast (site of earlysynthesis) and the cytoplasmic lipid vesicles. Here the intermediatetransported across the chloroplast envelope into the cytoplasm is elucidatedby means of the inhibitors diphenylamine (DPA) and2-(4-chlorophenylthio)-triethylamine (CPTA). Based on the amounts of theintermediates accumulated upon inhibitor treatment and their occurrencein the lipid vesicle fractions, it is concluded that the transport takes placeafter β-ionone ring cyclization. A non-vesicle mechanism of β-iononecarotenoid transport from the chloroplast towards the cytoplasmic lipidvesicles via carotenoid binding proteins is suggested.