Abstract
The photosynthesis-related plastid genes are transcribed mainly by PEP, in which plastid-encoded core enzyme (α2ββ'β") assembles with a nuclear-encoded σ factor to recognize the specific promoters for transcription initiation. In Arabidopsis, there occur six σ factor genes, Sig1-6, which might development- and environment-dependently regulate the plastid-gene transcription through their differential expression. We examined the effect of lights on Sig1, Sig2 and Sig5 transcript induction in Arabidopsis leaves. In contrast to the cryptochrome-mediated (470nm,10 μmolm-2s-1) rapid induction of Sig5 and Sig1 transcripts, red-light illumination (660nm) more slowly induced Sig1 and Sig2 transcripts to their blue light-levels. The red-light induction of Sig1 and Sig2 was stronger at 5 μmolm-2s-1 than 50 μmolm-2s-1. Under either light illumination Sig2 transcripts were slowly induced, but more stable compared with Sig5 and Sig1 transcripts which were rapidly degraded upon the subsequent dark-treatment. Thus, these Sig genes differ in the light-induced transcription profile and the transcript stability.
