Heat stress: an overview of molecular responses in photosynthesis

Abstract

The primary targets of thermal damage in plants are the oxygen evolving complex along with the associated cofactors in photosystem II (PSII), carbon fixation by Rubisco and the ATP generating system. Recent investigations on the combined action of moderate light intensity and heat stress suggest that moderately high temperatures do not cause serious PSII damage but inhibit the repair of PSII. The latter largely involves de novo synthesis of proteins, particularly the D1 protein of the photosynthetic machinery that is damaged due to generation of reactive oxygen species (ROS), resulting in the reduction of carbon fixation and oxygen evolution, as well as disruption of the linear electron flow. The attack of ROS during moderate heat stress principally affects the repair system of PSII, but not directly the PSII reaction center (RC). Heat stress additionally induces cleavage and aggregation of RC proteins; the mechanisms of such processes are as yet unclear. On the other hand, membrane linked sensors seem to trigger the accumulation of compatible solutes like glycinebetaine in the neighborhood of PSII membranes. They also induce the expression of stress proteins that alleviate the ROS-mediated inhibition of repair of the stress damaged photosynthetic machinery and are required for the acclimation process. In this review we summarize the recent progress in the studies of molecular mechanisms involved during moderate heat stress on the photosynthetic machinery, especially in PSII.

Population Parameters and Path-Coefficient Analysis of Tomato Grown under Heat Stress

“…A significant positive association 0.799 with high coefficient coincidence 81.54% was estimated between ELV and ELF indicating the possibility of practicing of early selection for heat stress tolerance at vegetative stage using electrolytes leakage as a form of indirect selection. Although leaf photosynthesis is one of the most physiological process affected by heat stress (Wahid et al 2007, Allakhverdiev et al 2008, our results showed that photosynthesis parameters; chlorophyll a/b and chlorophyll/carotenoids ratios, could not reflect a straight association of this effect with any of the studied traits.…”

Alterations in photochemical efficiency of photosystem II in wheat plant on hot summer day

“…Increasing temperature brings damage to various aspects of photosynthetic functions, including both the photochemical reaction related to Photosystem I (PS I), Photosystem II (PS II) and the dark reactions. However, PS II is one of the most thermolabile components of the photosynthetic apparatus (Allakhverdiev et al 2008;Chen and Cheng 2009). Heat stress inhibits photosynthetic electron transport activity as well the function of the oxidizing side of PS II resulting in decreased oxygen evolution.…”

Light-stimulated heat tolerance in leaves of two neotropical tree species, Ficus insipida and Calophyllum longifolium

“…Furthermore, accumulation of PSII units containing inactivated D1 protein could cause quenching of F m . Repair of PSII has been found to be restricted by reactive oxygen species (ROS) under thermal stress as well as light stress due to inhibition of protein (primarily D1) resynthesis (see Murata et al 2007;Allakhverdiev et al 2008). However, the latter effect, resembling photoinhibition of PSII, should be reversible during 'recovery' (see below).…”

“…Upon a return to favourable conditions (i.e. under low light at moderate temperatures), photodamaged PSII can be repaired; in particular, inactivated D1 protein in the reaction centre is degraded, followed by reconstitution of PSII with newly synthesised D1 (see Allakhverdiev et al 2008;Takahashi and Badger 2011;Murata et al 2012). The common reversibility of photoinhibition in low light speaks against a purely destructive mechanism.…”