Turn over regulation of photosystem II proteins by the light-dependent transcription in chloroplasts

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Photosynthesis related genes encoded by plastid genome are transcribed by a plastid-encoded plastid RNA polymerase (PEP). However, no transcription factor is encoded by plastid genome, It is likely that nuclear encoded transcription factors, for example plastid sigma factors, are involved in the regulation of plastid gene transcription. In this work, we analyzed fine structure of several PEP promoters by in vitro transcription and plastid transformation and revealed the role of nuclear-encoded transcription factors on plastid promoter recognition. We also studied the signal transduction involved in nuclear-encoded photosynthesis genes and the regulation of the electron transfer in photosystem II.RESULTSThe psbD promoter upstream of the psbD gene encoding photosystem II D2 protein is reversibly activated by light and regulated by endogenous circadian rhythm, too. There are two transcription enhancing elements upstream of -35 element, but the promoter core is likely to be involved in the light-dependent and circadian- regulated transcription.The rbcL core promoter is sufficient for the light-dependent transcription. Furthermore, we revealed that reduced rbcL transcription in the dark is compensated by increased mRNA stability.Mesophyll cell specific nuclear-encoded cab-ml expression is controlled by cytosolic Ca^<2+> level. Ca^<2+> signaling is mediated by a 54-bp sequence in the 5' flanking region.Photosystem II PsbL is involved in electron transfer at the donor side from Tyr-Z to P_<680>^+. Amino acid residues in the carboxyl-terminal region is essential for the PsbL function.