Lipid Composition of Photosystem I and II in the Tobacco Mutant Nicotiana tabacum NC 95

Abstract

The lipids of photosystem II particles, of chloroplasts and leaves are compared in the variegated tobacco mutant NC 95. The mutant differs from other N. tabacum mutants by the phenomenon that it has variegated leaves with green and with yellow-green leaf patches. Chloroplasts from the green leaf areas exhibit photosystem II and photosystem I reactions and have a normal lamellar system with grana and intergrana regions. Chloroplasts from the yellow-green leaf areas, however, yield only photosystem I reactions and have only single stranded isolated thylakoids. Hence, this mutant offers the unique possibility to compare without the use of detergents within the same plant the lipid composition of photosystem II particles with that in intact chloroplasts, exhibiting either photosystem II and I reactions or those exhibiting exclusively photosystem I reactions. The lipids of photosystem II particles are composed of 37 % glycolipids, 4 % phospholipids, 5 % carotenoids and 54 % chlorophyll. Lipids of chloroplasts with grana stacking are composed of 75% glycolipids, 7 % phospholipids, 2 % carotenoids and 16% chlorophyll. Chloroplasts with single isolated thylakoids have a lipid composition consisting of 8 3 % glycolipids, 14% phospholipids and only 0.5% carotenoids and 2 % chlorophyll. The chloroplast lipid mixture is characterized in comparison to the respective leaf lipid mixture by a 16-17% higher glycolipid portion and by a 13-70% lower phospholipid content. The main difference in the lipid composition of photosystem I and II consists in the observation that chloroplasts active in only photosystem I contain more than double the amount of glycolipids and the 4-fold amount of phospholipids in comparison to photosystem II active preparations. The amount of monogalactolipid is even 3 times higher in chloroplasts active only in photosystem I when compared to those in photosystem II particles. In photosystem II particles phosphatidylethanolamine is completely lacking and phosphatidylglycerol and phosphatidylinositol occur only in traces. The fatty acids of the sulfolipid are by 45 % more saturated in the photosystem II particles and the digalactolipids of the photosystem II particles are by 28 % more saturated than in chloroplasts exhibiting photosystem I and II activity.