Biosynthesis of P700-Chlorophyll a Protein Complex, Plastocyanin, and Cytochrome b6/f Complex

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Abstract
Changes in the amount of P700-chlorophyll .alpha. protein complex, plastocyanin, and cytochrome b6/f complex during greening of pea (Pisum sativum L.), wheat (Triticum aestivum L.), and barley (Hordeum vulgare L.) leaves were analyzed by an immunochemical quantification method. Neither subunit I and II of P700-chlorophyll .alpha. protein complex could be detected in the etiolated seedlings of all three plants and the accumulation of these subunits was shown to be light dependent. On the other hand, a small amount of plastocyanin was present in the etiolated seedlings of all three plants and its level increased about 30-fold during the subsequent 72-hour greening period. Furthermore, cytochrome f, cytochrome b6, and Rieske Fe-S center protein in cytochrome b6/f complex were also present in the etiolated seedlings of all three plants. The level of each subunit component increased differently during greening and their induction pattern different from species to species. The accumulation of cytochrome b6/f complex was most profoundly affected by light in pea leaves, and the levels of cytochrome f, cytochrome b6, and Rieske Fe-S center protein increased during greening about 10-, 20-, and more than 30-fold, respectively. In comparison to the case of pea seedlings, in wheat and barley leaves the level of each subunit component increased much less markedly. The results suggest that light regulates the accumulation of not only the chlorophyll protein complex but also the components of the electron transport systems.