Biogenesis of photosystem I reaction center during greening of oat, bean and spinach leaves

Abstract

The relative amounts of some chloroplast polypeptides were followed during greening of leaves from three different plant families. Oat, bean and spinach were the representatives of the Gramineae, Leguminosae and Chenopodiaceae, respectively. By using specific antibodies against subunits of the chloroplast protein complexes, it was found with that method that the protein complexes which are not involved in a photobiochemical reaction were synthesized in etiolated leaves and their amounts did not significantly change during greening. Examples of these are the large and small subunits of ribulose 1,5-bisphosphate carboxylase, the subunits of the chloroplast coupling factor (CF1) and cytochrome b6-f complex. On the other hand, in photosystem I reaction center, the synthesis of subunits II, III, IV and V was found to be induced by light. Sequential synthesis of these subunits was observed. Subunit II is the first to be synthesized after exposing the plants to light. The synthesis of subunits III, IV and V followed the synthesis of subunit II in this order. Subunit I of photosystem I reaction center was present in etiolated leaves and its amount was not significantly altered during the first few hours of greening.