Regulation of plastid photosynthetic psbK‐I‐D‐C gene expression by light in rice plants

Abstract

The expression of the plastid photosynthetic psbK‐I‐D‐C gene cluster is closely regulated by light. The time courses of expression of the gene cluster in rice seedlings (Oryza sativa L. cv. Tainong 67) grown under various irradiation regimes were examined by northern and western blot analyses. The data indicated that the gene cluster is photoregulated at the transcriptional and post transcriptional levels. Blue light not only enhanced the accumulation of the overlapping transcripts present in the 7 to 8‐day dark‐grown seedlings, but also induced the accumulation of new class d transcripts encoding D2 protein and CP43. This observation confirms the conservation of blue‐light regulation of psbD‐psbC transcription in plants. In etiolated seedlings, the accumulation of class e transcript encoding CP43 increased most remarkably during development: irradiation further enhanced the transcript level. Although the transcripts encoding D2 protein and CP43 are present in etiolated plants, only D2 protein is accumulated, and CP43 was not detected unless the seedlings were exposed to light. The transcript levels of RNAs d1 and f2 in green seedlings grown under a 12‐h photoperiod exhibited fluctuating patterns over the 24‐h period. The levels o1 RNAs dl and f2 also exhibited significant fluctuation during the 36‐h exposure of the etiolated seedlings to light. These data imply that the circadian regulation of pshD‐psbC expression takes place at the transcriptional and post‐transcriptional levels.