Photosynthetic redox control of nuclear gene expression

Abstract

Chloroplasts contain 3000-4000 different proteins but only a small subset of them is encoded in the plastid genome while the majority is encoded in the nucleus. Expression of these genes therefore requires a high degree of co-ordination between nucleus and chloroplast. This is achieved by a bilateral information exchange between both compartments including nucleus-to-plastid (anterograde) and plastid-to-nucleus (retrograde) signals. The latter represent a functional feedback control which couples the expression of nuclear encoded plastid proteins to the actual functional state of the organelle. The efficiency of photosynthesis is a very important parameter in this context since it is influenced by many environmental conditions and therefore represents a sensor for the residing environment. Components of the photosynthetic electron transport chain exhibit significant changes in their reduction/oxidation (redox) state depending on the photosynthetic electron flow and therefore serve as signalling parameters which report environmental influences on photosynthesis. Such redox signals control chloroplast and nuclear gene expression events and play an important role in the co-ordination of both genetic compartments. It is discussed here which photosynthetic parameters are known to control nuclear gene expression, how these signals are transduced toward the nucleus, and how they interact with other plastid retrograde signals and cytosolic light perception systems.

ArabidopsisSTN7 Kinase Provides a Link between Short- and Long-Term Photosynthetic Acclimation

“…The regulatory coupling of state transitions to the LTR (Allen and Pfannschmidt, 2000;Pursiheimo et al, 2001) and the dependence of both processes on STN7 activity are compatible with the view that the signal pathways leading to state transitions and LTR represent a hierarchically organized signaling cascade (Fey et al, 2005a), where changes in PQ redox state trigger first state transitions and then the LTR via a STN7-dependent phosphorylation cascade (and/or reversible relocation of protein complexes). Indeed, the inability of psad1-1 and psae1-3 to adapt to changes in light conditions appears to be the direct Measurements were performed as described in Methods.…”

“…Like state transitions, the LTR is triggered by the redox state of the PQ pool, and in Arabidopsis it is mainly mediated by changes in the number of PSI complexes that are thought to be caused by altered expression of the corresponding plastid-and nucleusencoded proteins (Fey et al, 2005a). As a consequence, the chlorophyll a/b ratio and the chlorophyll fluorescence parameter F s /F m (reflecting the structural differences in the photosynthetic apparatus as described in Results and Methods) were found to be useful for assessing the ability of plants to perform a proper LTR .…”

The Arabidopsis Spontaneous Cell Death1 gene, encoding a ζ-carotene desaturase essential for carotenoid biosynthesis, is involved in chloroplast development, photoprotection and retrograde signalling

“…This regulatory mechanism, known as retrograde signaling, has been shown to involve the transduction of a signal from the plastid to nucleus [32]. Notably, the plastid-generated signals were shown to be chlorophyll biosynthetic precursors, chloroplast redox states and ROS [32][33][34][35][36], all of which are related to carotenoid metabolism. Therefore, carotenoids are involved in the regulation of a large repertoire of physiological processes in higher plants.…”

Chlamydomonas reinhardtii PsbS Protein Is Functional and Accumulates Rapidly and Transiently under High Light

“…We cannot exclude a role of the redox state of the plastoquinone (PQ) on PsbS accumulation. However, this possibility is less likely since the PQ redox state is mainly involved in optimizing photosynthesis under not saturating light conditions, such as during state transitions, or during long-term acclimation (Fey et al, 2005;Adamiec et al, 2008). Moreover, our result (Fig.…”