Abstract
Chloroplasts have their own DNA and gene expression systems. In order to study transcriptional regulation, genetic approaches have been historically used. However, this approach may include some indirect effects, which make it difficult to understand specific regulation by the transcription factors. Chromatin immunoprecipitation (ChIP) is a powerful and useful tool that can obtain information for binding sites for transcription factors, and directly detect dynamic changes of their interaction patterns in vivo.
To further understand the roles of plastid sigma factors in Arabidopsis thaliana, we here developed ChIP-based method, and analyzed binding pattern of SIG5, a stress-induced chloroplast sigma factor. We found SIG5 specifically binds to novel target promoters as well as psbA or psbD BLRP that are already known, and this binding depends on several kinds of stress conditions. We further analyzed and identified target promoters for SIG1, an essential sigma factor by ChIP analysis. These results suggest that ChIP analysis is useful to understand transcriptional regulation of chloroplast genes, which can overcome several problems from traditional methods.
