Cyclic electron flow may provide some protection against PSII photoinhibition in rice ( Oryza sativa L.) leaves under heat stress

Abstract

Previously we have shown that a quick down-regulation in PSI activity compares to that of PSII following short-term heat stress for two rice groups including C4023 and Q4149, studied herein. These accessions were identified to have different natural capacities in driving cyclic electron flow (CEF) around PSI; i.e., low CEF (lcef) and high CEF (hcef) for C4023 and Q4149, respectively. The aim of this study was to investigate whether these two lines have different mechanisms of protecting photosystem II from photodamage under heat stress. We observed a stepwise alteration in the shape of Chl a fluorescence induction (OJIP) with increasing temperature treatment. The effect of 44°C treatment on the damping in Chl a fluorescence was more pronounced in C4023 than in Q4149. Likewise, we noted a disruption in the I-step, a decline in the F due to a strong damping in the F, and a slight increase in the F. Normalized data demonstrated that the I-step seems more susceptible to 44°C in C4023 than in Q4149. We also measured the redox states of plastocyanin (PC) and P by monitoring the transmission changes at 820nm (I), and observed a disturbance in the oxidation/reduction kinetics of PC and P. The decline in the amplitude of their oxidation was shown to be about 29% and 13% for C4023 and Q4149, respectively. The electropotential component (Δφ) of ms-DLE appeared more sensitive to temperature stress than the chemical component (ΔpH), and the impact of heat was more evident and drastic in C4023 than in Q4149. Under heat stress, we noticed a concomitant decline in the primary photochemistry of PSII as well as in both the membrane energization process and the lumen protonation for both accessions, and it is evident that heat affects these parameters more in C4023 than in Q4149. All these data suggest that higher CET can confer higher photoprotection to PSII in rice lines, which can be a desirable trait during rice breeding, especially in the context of a "warming" world.

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Isoprene Acts as a Signaling Molecule in Gene Networks Important for Stress Responses and Plant Growth

“…Both proteins have been shown to be essential to stabilize PSII, especially under high and fluctuating light stress (Liu and Last, 2015a, 2015b. In this study, isoprene also affected the gene expression of subunits of the NADH dehydrogenase-like complex in the chloroplast, which is associated with PSI and mediated the cyclic electron transport important for protecting PSI against photoinhibition under normal and high-temperature stress (Peng et al, 2009(Peng et al, , 2012Shikanai, 2016;Essemine et al, 2017). As mentioned above, isoprene also altered a number of genes coding for ribosomal proteins in chloroplasts that promote chloroplast development and Chl synthesis.…”

Illuminating the role of the Gα heterotrimeric G protein subunit, RGA1, in regulating photoprotection and photoavoidance in rice

“…Whereas photoinhibitory damage to PSII is reversible, damage to PSI is believed to be essentially irreversible (Tikkanen et al, ). An increased rate of cyclic electron transport around PSI contributes to the protection of PSI (Essemine, Xiao, Qu, Mi, & Zhu, ; W. Huang, Yang, Hu, Zhang, & Cao, ; Yamori & Shikanai, ). Transcriptome analysis supports a higher rate of cyclic electron transport relative to linear electron transport in d1 (Figure , Supporting Information Table S22).…”