Metabolic Reprogramming in Chloroplasts under Heat Stress in Plants

Abstract

Increases in ambient temperatures have been a severe threat to crop production in many countries around the world under climate change. Chloroplasts serve as metabolic centers and play a key role in physiological adaptive processes to heat stress. In addition to expressing heat shock proteins that protect proteins from heat-induced damage, metabolic reprogramming occurs during adaptive physiological processes in chloroplasts. Heat stress leads to inhibition of plant photosynthetic activity by damaging key components functioning in a variety of metabolic processes, with concomitant reductions in biomass production and crop yield. In this review article, we will focus on events through extensive and transient metabolic reprogramming in response to heat stress, which included chlorophyll breakdown, generation of reactive oxygen species (ROS), antioxidant defense, protein turnover, and metabolic alterations with carbon assimilation. Such diverse metabolic reprogramming in chloroplasts is required for systemic acquired acclimation to heat stress in plants.

Sensitivity and Responses of Chloroplasts to Heat Stress in Plants

“…This is mainly reflected in the distinct alteration to the redox state related to the injury of thylakoid membranes (Berry and Bjorkman, 1980;Biswal et al, 2011). At high temperatures, the photochemical reactions in the thylakoid lamellae and carbon metabolism in the stroma of chloroplasts are most affected (Wise et al, 2004;Wang et al, 2018). Heat stress could directly damage the photosynthetic apparatus, such as PSI and PSII, the cytochrome b6f (Cytb6f) complex and Rubisco (Havaux, 1993a,b;Wise et al, 2004); moreover, heat-induced inactivation of these FIGURE 1 | Sensitivity and responses of chloroplasts under heat stress.…”

“…Studies have shown that degradation of Chl could protect plant cells from the hazardous effects of phototoxic pigments (Ginsburg et al, 1994;Hörtensteiner, 2006Hörtensteiner, , 2009. Under normal growth conditions, the synthesis and degradation of Chl reach equilibrium and the levels of this molecule remain stable (Ginsburg et al, 1994;Hörtensteiner, 2006;Wang et al, 2018). Conversely, when plants are subject to environmental stress, including heat, the content of Chl decreases, leading to leaf senescence or chlorosis Lim et al, 2007;Allakhverdiev et al, 2008;Rossi et al, 2017).…”

“…Conversely, when plants are subject to environmental stress, including heat, the content of Chl decreases, leading to leaf senescence or chlorosis Lim et al, 2007;Allakhverdiev et al, 2008;Rossi et al, 2017). Under heat treatment, the activity of chlorophyllase and Chl-degrading peroxidase dramatically increases, resulting in a serious reduction in Chl levels (Figure 2; Wang et al, 2018). One study demonstrated that the exogenous application of zeatin riboside (ZR) increases Chl levels by reducing the activity of protease in creeping bentgrass during heat stress (Figure 2; Veerasamy et al, 2007).…”

Enhanced tolerance to a combination of heat stress and drought in Arabidopsis plants deficient in ICS1 is associated with modulation of photosynthetic reaction center proteins

“…Under drought, the dark reactions can be inhibited as a result of the insufficient availability of CO 2 due to stomatal closure, and the high photosynthetic energy absorbed by the plant enhances oxygen reduction and ROS production (Mittler , Mittler et al , Pinto‐Marijuan and Munne‐Bosch ). Heat stress can inhibit the activity of the Calvin–Benson cycle enzymes, and result in over‐reduction of photosystems (Yamori , Wang et al ). In addition, the negative impacts on photosynthetic machineries were exacerbated when drought was combined with high temperature (Arend et al ).…”

Eco-Physiological Screening of Different Tomato Genotypes in Response to High Temperatures: A Combined Field-to-Laboratory Approach

“…However, it cannot be excluded that the significant reduction of F v /F m observed in some genotypes may also be associated with photoprotection mechanisms, as indicated by NPQ values that peaked in correspondence to the reduction in F v /F m . Simultaneously, protective mechanisms are activated to protect the D1 protein, such as the expression of heat shock proteins (HSPs) like HSP21 that directly binds D1 to shield it against damage [32]. However, this does not seem to be the case for the genotype BG1620, which was the most affected by the severe decline of photochemical and non-photochemical processes.…”