THE CRITICAL REQUIREMENT FOR LINOLENIC ACID IS POLLEN DEVELOPMENT, NOT PHOTOSYNTHESIS, IN AN ARABIDOPSIS MUTANT

The very high proportions of trienoic fatty acids found in chloroplast membranes of all higher plants suggest that these lipid structures mi ght be essential for photosynthesis. We report here on the production of Arabidopsis triple mutants that contain negligible levels of trieno ic fatty acids. Photosynthesis at 22 degrees C was barely affected, an d vegetative growth of the mutants was identical with that of the wild type, demonstrating that any requirement for trienoic acyl groups in membrane structure and function is relatively subtle. Although vegetat ive growth and development were unaffected, the triple mutants are mal e sterile and produce no seed under normal conditions. Comparisons of pollen development in wild-type and triple mutant flowers established that pollen grains in the mutant developed to the tricellular stage. E xogenous applications of alpha-linolenate or jasmonate restored fertil ity. Taken together, the results demonstrate that the critical role of trienoic acids in the life cycle of plants is as the precursor of oxy lipin, a signaling compound that regulates final maturation processes and the release of pollen.