Photosynthetic acclimation: Does the dynamic structure and macro‐organisation of photosystem II in higher plant grana membranes regulate light harvesting states?

Abstract

The efficiency of light harvesting in higher plant photosynthesis is regulated in response to external environmental conditions. Under conditions of excess light, the normally highly efficient light‐harvesting system of photosystem II is switched into a state in which unwanted, potentially harmful, energy is dissipated as heat. This process, known as nonphotochemical quenching, occurs by the creation of energy quenchers following conformational change in the light‐harvesting complexes, which is initiated by the build up of the thylakoid pH gradient and controlled by the xanthophyll cycle. In the present study, the evidence to support the notion that this regulatory mechanism is dependent upon the organization of the different antenna subunits in the stacked grana membranes is reviewed. We postulate that nonphotochemical quenching occurs within a structural locus comprising the PsbS subunit and components of the light‐harvesting antenna, CP26, CP24, CP29 and LHCIIb (the major trimeric light‐harvesting complex), formed in response to protonation and controlled by the xanthophyll cycle carotenoids.

Transgressive physiological and transcriptomic responses to light stress in allopolyploid Glycine dolichocarpa (Leguminosae)

“…This model was chosen because NPQ induction is known to involve two distinct phases, the first triggered by protonation of the PsbS protein and the second resulting from deepoxidation of violaxanthin to zeaxanthin (Horton et al, 2008;Nilkens et al, 2010). Coefficients of determination (R 2 ) between this model and the data, as calculated by SigmaPlot, were consistently higher than for single component models, and raw residuals between fitted and observed data were more randomly distributed (data not shown), indicating a better fit to the data.…”

“…Both PsbS and VDE require a low lumenal pH for activation (Szabo et al, 2005;Horton et al, 2008). Photosynthetic electron transport contributes H þ to the thylakoid lumen via the Q cycle at the cytochrome b 6 f complex and water splitting at PSII.…”

Correlation of Car S1 → Chl with Chl → Car S1 Energy Transfer Supports the Excitonic Model in Quenched Light Harvesting Complex II

“…Several studies suggest that, apart from light harvesting and energy transfer, LHCII plays a key role in the regulation of qE by switching it into a quenched state due to mechanisms that are so far not completely understood. 6,13 In these studies it has been proposed that interactions between carotenoids and chlorophylls may create dissipation valves for excess excitation energy. 7,14 Other studies have presented evidence for minor antennae complexes as main regulators.…”

The galactolipid monogalactosyldiacylglycerol (MGDG) contributes to photosynthesis-related processes inArabidopsis thaliana

“…This change is further stabilized by the de-epoxidation of violaxanthin to zeaxanthin by the luminal VDE. 28 However, the thermal dissipation is impaired in mgd1-1 mutants at high light intensities (>1000 μmol m -2 s -1 ) making them more susceptible to light stress. Surprisingly, this is not mediated by direct effects on VDE and PsbS activities, but by changes in the proton conductivity of the thylakoid membrane.…”

“…13 During short-term high light stress, antheraxanthin and zeaxanthin are thought to facilitate dissipation of excess light energy in the PSII antenna bed by non-photochemical quenching. 27,28 Upon high light stress the pH decreases, triggering photoprotective mechanisms via changes in the PSII antenna system. The PsbS protein, which is involved in thermal dissipation, is protonated and initiates Processes putatively dependent on the galactolipid monogalactosyldiacylglycerol (MGDG) were recently studied using the knockdown monogalactosyldiacylglycerol synthase 1 (mgd1-1) mutant (~40% reduction in MGDG).…”