Physiological Factors Affecting the Accumulation of Plastocyanin, Cytochrome c-552, and a 30-kD Soluble Protein in Chlamydomonas reinhardtii
The accumulation of several proteins involved in photosynthesis is controlled by physiological factors which are generated either internally by ongoing developmental programs or externally by the environment. The dependence of photosynthesis on metal ions such as Cu, Mn, and Fe is well documented . The suggestion that these ions might serve as regulators of the assembly of some components of the photosynthetic apparatus follows the early work of Wood  who demonstrated that, depending on the availability of Cu in the growth medium, either the Cu-protein plastocyanin (PC) or the heme-protein cytochrome c-552 of Chlamydomonas reinhardtii can function as electron carriers between the cyt b6/f complex and PSI. Cells of C. reinhardtii supplemented with physiological concentrations of Cu accumulate PC but lack cyt c-552 (Figure 1). In Cu-deficient medium, alternatively, cyt c-552 accumulates concomitantly with a decrease in PC levels. Previously we have shown that at least two different Cu-responsive mechanisms govern the reciprocal expression of these two proteins . PC accumulation is controlled at the post-translational level by a mechanism involving the rapid degradation of apoPC . In contrast, the accumulation of cyt c-552 in response to Cu is managed at the level of stable cyt c-552 messenger RNA [3,5].
KeywordsTotal Soluble Protein Physiological Factor Reciprocal Expression Transcript Initiation Inorganic Plant Nutrition
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- 1.Sandmann, G. and Boger, P. (1983) In Encylopedia of Plant Physiology New Series. Inorganic Plant Nutrition (Lauchli, A. and Bieleski, R. L., eds.) Vol. 15B, pp. 563–596.Google Scholar