Chloroplast Redox Control of Nuclear Gene Expression—A New Class of Plastid Signals in Interorganellar Communication

Institute of General Botany, Department of Plant Physiology, University of Jena, Jena, Germany.
Antioxidants and Redox Signaling (Impact Factor: 7.41). 03/2003; 5(1):95-101. DOI: 10.1089/152308603321223586
Source: PubMed


Chloroplasts are genetically semiautonomous organelles that contain their own subset of 100-120 genes coding for chloroplast proteins, tRNAs, and rRNAs. However, the great majority of the chloroplast proteins are encoded in the nucleus and must be imported into the organelle after their translation in the cytosol. This arrangement requires a high degree of coordination between the gene expression machineries in chloroplasts and nucleus, which is achieved by a permanent exchange of information between both compartments. The existence of such coordinating signals has long been known; however, the underlying molecular mechanisms and signaling routes are not understood. The present data indicate that the expression of nuclear-encoded chloroplast proteins is coupled to the functional state of the chloroplasts. Photosynthesis, which is the major function of chloroplasts, plays a crucial role in this context. Changes in the reduction/oxidation (redox) state of components of the photosynthetic machinery act as signals, which regulate the expression of chloroplast proteins in both chloroplasts and nucleus and help to coordinate the expression both in compartments. Recent advances in understanding chloroplast redox regulation of nuclear gene expression are summarized, and the importance for intracellular signaling is discussed.

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    • "In fully matured chloroplasts, a functional regulation that depends on environmental cues such as light variations becomes more dominant. This functional regulation is mediated mainly by the chloroplast itself, for instance by redox signals from photosynthesis (Pfannschmidt et al., 2003). The orchestration of the different transcription machineries, thus, Fig. 1. "
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    • "Molecular mechanisms of redox-sensitive regulation of protein have also been explained for plants and other living organisms (Cvetkovska et al., 2005; Foyer and Noctor, 2005). ROS mediated signaling involves hetero-trimeric G-proteins and MAP kinase regulated protein phosphorylation and protein Tyr phosphatases (Pfannschmidt et al., 2003; Foyer and Noctor, 2005; Kiffin et al., 2006). Mitogen-activated protein kinase (MAPK) cascades are mainly engaged by eukaryotes which have got much concentration for research since long years. "
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    • "It was demonstrated that the gun4 mutation affects the composition of the PSI core complex, which leads to imbalanced excitation pressure between two photosystems (Formighieri et al., 2012). Changes in the redox state of plastid electron transfer chain (ETC) components were shown to be involved in the retrograde signalling (Pfannschmidt et al., 2003; Brautigam et al., 2009; Lemeille and Rochaix, 2010). Thus, hypothetically, the deregulated gene expression in the strain lacking GUN4 might be the effect of retrograde signals originating from the changes in redox state of the photosynthetic ETC; however, as observed in gun4, a general upregulation of tetrapyrrole biosynthesis and PhAN genes would not be expected in response to an over-reduction of ETC components. "
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