Perturbation of Fungal Growth and Lipid Composition by Cyclopropenoid Fatty Acids

Cyclopropenoid fatty acids (CPE) are found in at least two phylogenetically distant groups of plants [1, 2, 10]. Although they are best known as components of seed oils, CPE do occur in vegetative plant parts [5, 10, 12]. We have found that, in representatives of seven Malvaceous genera, CPE are more concentrated in roots than in shoot tissues [9]. In Malva negiecta, for example, malvalate and sterculate together comprise 53% of root neutral lipids, 14% in the stem, 4% in petioles, and <2% in leaf blades. Phospholipids contain far smaller proportions of CPE, but the same distribution pattern holds. In M. neglecta, CPE make up 7.5% of root phospholipids, but only 0.1% of leaf blade phospholipids. Since root CPE also exceed shoot CPE on a dry weight basis, it seems unlikely that the low proportions in leaves are due merely to masking by chloroplast lipids. Nor does CPE content strictly parallel triacylglycerol (TAG) content of the organs. In cotyledons from cotton seeds, which are quite rich in TAG, CPE make up less than 0.1% of neutral lipid acyl groups. Radicles from the same seeds contain 26% CPE, while hypocotyls, like stems, have intermediate levels.