Impact of Plastid Differentiation on Transcription of Nuclear and Mitochondrial Genes

Abstract

In plant cells the regulation of nuclear and chloroplast gene expression occurs in a coordinated manner. The transcription of certain nuclear genes has been shown to be affected by the state of chloroplast development. The signal molecules and transcription factors involved have not yet been identified. Mutant plants without a functional translational apparatus in their plastids, such as the barley albostrians mutant, provide a valuable experimental system for studying the effects of plastid differentiation on nuclear gene expression. Results of studies on this mutant are summarized. They indicate that the plastid has a much more complex influence on nuclear gene expression than was previously thought. The plastid was also observed to have an impact on the level of mitochondrial transcripts. The existence of several plastid-derived signal chains affecting the transcription of a large number of nuclear genes is proposed. These signal chains might not only respond to the developmental state of the plastids/chloroplasts, but also to changes in plastid metabolism and redox state as well as to oxidative stress. The data are discussed in the context of recent ideas about chloroplast-nuclear interactions.