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First published online August 11, 2006; 10.1104/pp.106.085878 Plant Physiology 142:642-650 (2006) © 2006 American Society of Plant Biologists OPEN ACCESS ARTICLE
Dual Temporal Role of Plastid Sigma Factor 6 in Arabidopsis Development1,[OA]Plant Cell Physiology, University of Bochum, D44780 Bochum, Germany
Plants contain nuclear-coded sigma factors for initiation of chloroplast transcription. The in vivo function of individual members of the sigma gene family has become increasingly accessible by knockout and complementation strategies. Here we have investigated plastid gene expression in an Arabidopsis (Arabidopsis thaliana) mutant with a defective gene for sigma factor 6. RNA gel-blot hybridization and real-time reverse transcription polymerase chain reaction together indicate that this factor has a dual developmental role, with both early and persistent (long-term) activities. The early role is evident from the sharp decrease of certain plastid transcripts only in young mutant seedlings. The second (persistent) role is reflected by the up- and down-regulation of other transcripts at the time of primary leaf formation and subsequent vegetative development. We conclude that sigma 6 does not represent a general factor, but seems to have specialized roles in developmental stage- and gene-specific plastid transcription. The possibility that plastid DNA copy number might be responsible for the altered transcript patterns in mutant versus wild type was excluded by the results of DNA gel-blot hybridization. Retransformation of the knockout line with the full-length sigma 6 cDNA further established a causal relationship between the functional sigma gene and the resulting phenotype.
1 This work was supported by the Deutsche Forschungsgemeinschaft (SFB 480). The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Gerhard Link (gerhard.link{at}ruhr-uni-bochum.de). [OA] Open Access articles can be viewed online without a subscription. www.plantphysiol.org/cgi/doi/10.1104/pp.106.085878 * Corresponding author; e-mail gerhard.link{at}ruhr-uni-bochum.de; fax 492343214188. Received June 27, 2006; accepted August 1, 2006; published August 11, 2006. This article has been cited by other articles:
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