Oligomeric form of the light-harvesting chlorophyll a + b-protein complex CP II, phosphatidyldiacylglycerol, Δ3- trans-hexadecenoic acid and energy transfer in Chlamydomonas reinhardtii, wild type and mutants

Abstract

Analyses of chlorophyll-protein complexes and of lipids were performed with the wild type of Chlamydomonas reinhardtii and three non-photosynthetic mutants: Fl 39, which was a ‘classical’ high-fluorescent Photosystem II (PS II)-lacking mutant, and mf 1 and mf 2, which lacked also functional PS II but were low-fluorescent and showed an abnormally predominant energy transfer from the main light-harvesting antenna towards Photosystem I. An oligomeric form of the chlorophyll a + b-protein complex CP II was clearly isolated from the wild type and the mutant Fl 39 but it was not detected in the mutants mf 1 and mf 2. The three mutants showed total lipid contents close to or greater than that of the wild type. Their phosphatidyldiacylglycerol (PG) contents, on a chlorophyll basis, were higher ( Fl 39) or 1.4- ( mf 1) and 2.0- ( mf 2) times lower than that of the wild type. The fatty acid compositions of the wild type and of the mutant Fl 39 were comparable, showing about equal amounts of a C18 series and a C16 series which included the Δ3- trans-hexadecenoic acid (C16:1- trans). This C16:1- trans was not detected in the mutants mf 1 and mf 2 which contained the other fatty acids. These results indicate correlations between lack of C16:1- trans-containing PG, lack of an oligomeric form of CP II and an impaired mechanism of the regulation of excitation energy transfer from the main chlorophyll a + b antenna.