Chloroplast avoidance movement reduces photodamage in plants

Abstract

When plants are exposed to light levels higher than those required for photosynthesis, reactive oxygen species are generated in the chloroplasts and cause photodamage. This can occur even under natural growth conditions. To mitigate photodamage, plants have developed several protective mechanisms. One is chloroplast avoidance movement, in which chloroplasts move from the cell surface to the side walls of cells under high light conditions, although experimental support is still awaited. Here, using different classes of mutant defective in chloroplast avoidance movement, we show that these mutants are more susceptible to damage in high light than wild-type plants. Damage of the photosynthetic apparatus and subsequent bleaching of leaf colour and necrosis occur faster under high light conditions in the mutants than in wild-type plants. We conclude that chloroplast avoidance movement actually decreases the amount of light absorption by chloroplasts, and might therefore be important to the survival of plants under natural growth conditions.

Plastid Movement Impaired 2, a New Gene Involved in Normal Blue-Light-Induced Chloroplast Movements in Arabidopsis

“…Accumulation along the periclinal cell walls under low-light conditions is believed to maximize light capture for photosynthesis, whereas the avoidance response to high light protects chloroplasts from photodamage by positioning chloroplasts in areas where light intensities are lowest (Zurzycki, 1961;Lechowski, 1974;Gorton and Vogelmann, 1996;Park et al, 1996;Trojan and Gabrys, 1996). Indeed, upon transfer to high light, Arabidopsis (Arabidopsis thaliana) mutants that lack light-induced chloroplast movements displayed signs of photodamage more rapidly than wild type (Kasahara et al, 2002).…”

PLASTID MOVEMENT IMPAIRED1 and PLASTID MOVEMENT IMPAIRED1-RELATED1 Mediate Photorelocation Movements of Both Chloroplasts and Nuclei

“…Under weak light conditions, chloroplasts move toward light to capture light efficiently (the accumulation response; Zurzycki, 1955). Under strong light conditions, chloroplasts escape from light to avoid photodamage (the avoidance response; Kasahara et al, 2002;Sztatelman et al, 2010;Davis and Hangarter, 2012;Cazzaniga et al, 2013). In most green plant species, these responses are induced primarily by the blue light receptor phototropin (phot) in response to a range of wavelengths from UVA to blue light (approximately 320-500 nm; for review, see Wada and Suetsugu, 2013;Kong and Wada, 2014).…”

Hacking the thylakoid proton motive force for improved photosynthesis: modulating ion flux rates that control proton motive force partitioning into Δ ψ and ΔpH

“…The electron and proton transfer processes can be highly efficient, but when energy capture outpaces the capacity of photosynthesis, a situation that can occur at high light and/or under adverse environmental conditions, reactive intermediates can accumulate in the photosynthetic apparatus, leading to generation of reactive oxygen species (ROS), mainly O 2 -• in PSI and mainly 1O2 in PSII, and these are responsible for oxidative photodamage. A range of photoprotective mechanisms have evolved to ameliorate photodamage and its effects, including nonphotochemical quenching (NPQ) processes such as the q E response (11), a complex cycle to repair damaged photosystem II (PSII) (12), chloroplast movements (13), cyclic electron flow (14,15), redox tuning to redirect back-reactions to non-ROS producing pathways (16,17) and alternative electron acceptor systems (18,19). Despite the diversity and complexity of these processes, in general they result in the loss of light energy, for example the decreased efficiency of light capture incurred by activation of NPQ (20), charge recombination (16), or the dissipation of redox energy when electrons are passed to the flavodiiron O 2 reductases (1).…”