Changes in Thylakoid Galactolipids and Proteins during Iron Nutrition-Mediated Chloroplast Development

Abstract

Changes in the amounts of thylakoid galactolipids and proteins were monitored for 96 h following Fe resupply to Fe-deficient sugar beet (Beta vulgaris L. cv F58-554H1) plants. During this period of Fe nutrition-mediated chloroplast development, the amount of galactolipid per leaf area increased linearly with time. Assuming galactolipids are an index for the amount of thylakoids, then there was a linear synthesis of thylakoid membranes during regreening. Total thylakoid protein synthesis lagged behind galactolipid synthesis, suggesting that proteins are inserted secondarily into the galactolipid matrix of the thylakoid membrane during development. Fe deficiency caused an increase in the free chlorophyll band under the conditions of gel electrophoresis used. Of the chlorophyll proteins resolved, the chlorophyll protein associated with photosystem I was most diminished in Fe-deficient tissue, and appeared to recover most rapidly. Changes in the light-harvesting chlorophyll proteins are also discussed. The number of polypeptides resolved by lithium dodecyl sulfate-polyacrylamide gel electrophoresis was higher in Fe-deficient thylakoids. During regreening, the number of resolved polypeptides decreased.