POLYUNSATURATED MEMBRANES ARE REQUIRED FOR PHOTOSYNTHETIC COMPETENCE IN A MUTANT OF ARABIDOPSIS

High levels of polyunsaturation are characteristic of all the membrane s of plant and animal cells. For example, the chloroplasts of leaf cel ls contain about 75-80% polyunsaturated fatty acids. For the extra-chl oroplast membranes in leaf cells and the membranes of non-photosynthet ic tissues, values of 60-65% are typical. We report here the productio n of Arabidopsis double mutants that contain negligible levels of poly unsaturated fatty acids. The mutants were not capable of autotrophic g rowth and produced extremely chlorotic cotyledons and leaves. However, on sucrose media, the double mutants were robust plants showing stron g leaf and root development. These observations indicate that the vast majority of receptor-mediated and transport-related membrane function s required to sustain the organism and induce proper development are a dequately supported in the absence of polyunsaturated lipids. By contr ast, photosynthesis is one process that does require high levels of me mbrane polyunsaturation.