PHOTOSYNTHETIC CHARACTERISTICS OF A MUTANT OF CHLAMYDOMONAS-REINHARDTII IMPAIRED IN FATTY-ACID DESATURATION IN CHLOROPLASTS

The photosynthetic apparatus of a mutant of Chlamydomonas reinhardtii, hf-9, impaired in fatty acid desaturation at the omega 6 position of fatty acids of chloroplasts was investigated. Measurement of photosynt hetic activities revealed that both PS I and PS II activities were red uced in hf-9. However, little alteration occurred in the contents and subunit assemblies of the PS I complex, PS II core complex and light-h arvesting complex of PS II. Lipids bound to these chlorophyll-protein (CP) complexes in hf-9 were shown to contain decreased levels of 16:4( 4,7,10,13) and 18:3(9,12,15), with accumulation of 16:1(7) and 18:1(9) , as compared with in the parent. Highly unsaturated fatty acids of ch loroplast lipids may be required for the normal functions of PS I and PS II, by associating with these complexes.