LIGHT-HARVESTING COMPLEX APOPROTEINS IN CYTOPLASMIC VACUOLES IN CHLAMYDOMONAS-REINHARDTII (CHLOROPHYTA)

Cells of Chlamydomonas reinhardtii Dangeard strain cw15arg7A contain e lectron-opaque material, often in the form of large granules, within c ytoplasmic vacuoles. Immunoelectron microscopy with antibodies to poly peptide II, a component of the major light-harvesting chlorophyll (Chi ) a/b-protein complex (LHCII) of thylakoid membranes,, revealed the pr esence of LHCII polypeptides within the chloroplast and in vacuolar ma terial in cells grown in the light. Vacuolar material was also heavily immunodecorated in dark-grown cells that did not synthesize Chl. Accu mulation of LHCII polypeptides was further studied in greening and lig ht-grown cells of a pale green mutant, deficient in LHCII, that was de rived from cw15arg7A by insertional mutagenesis. Light-grown cells of this mutant strain contained relatively few thylakoid membranes and sy nthesized LHCII polypeptides at a low rate. However, cytoplasmic vacuo les were immunoreactive. Appearance of mature-sized LHCII polypeptides in vacuoles suggested that these proteins were partially translocated across the envelope but not retained by the chloroplast without assem bly of LHCII.