Abstract
The photosynthetic light reactions provide energy that is consumed and stored in electron sinks, the products of photosynthesis. A balance between light reactions and electron consumption in the chloroplast is vital for plants, and is protected by several photosynthetic regulation mechanisms. Photosystem I (PSI) is particularly susceptible to photoinhibition when these factors become unbalanced, which can occur in low temperatures or in high light. In this study we used the pgr5 Arabidopsis mutant that lacks ΔpH-dependent regulation of photosynthetic electron transport as a model to study the consequences of PSI photoinhibition under high light. We found that PSI damage severely inhibits carbon fixation and starch accumulation, and attenuates enzymatic oxylipin synthesis and chloroplast regulation of nuclear gene expression after high light stress. This work shows that modifications to regulation of photosynthetic light reactions, which may be designed to improve yield in crop plants, can negatively impact metabolism and signalling, and thereby threaten plant growth and stress tolerance.This article is part of the themed issue ‘Enhancing photosynthesis in crop plants: targets for improvement’.
Highlights
The pressing need to improve plant productivity has prompted a focus on increasing photosynthetic yield
To this end we used an Arabidopsis thaliana mutant lacking the proton gradient regulation 5 (PGR5) protein, which is required for formation of a thylakoid membrane DpH under high light [19]
0 gl1 pgr5 (c) we investigated the production of 1O2 in thylakoids with electron paramagnetic resonance (EPR), using an 1O2-specific spin probe
Summary
The pressing need to improve plant productivity has prompted a focus on increasing photosynthetic yield. We addressed the role of proper regulation of photosynthetic electron transport reactions in the plant’s response to a changing light environment To this end we used an Arabidopsis thaliana mutant lacking the proton gradient regulation 5 (PGR5) protein, which is required for formation of a thylakoid membrane DpH under high light [19]. We confirm that imbalanced accumulation of electrons in the electron transport chain rapidly induces PSI damage in pgr5 [17,22] and demonstrate the broad and severe effects on primary and secondary metabolism, as well as on chloroplast signalling and nuclear gene expression Deeper understanding of these processes is required to avoid unexpected fitness penalties, and is a key step in developing sustainable strategies for more efficient utilization of photosynthesis in crop plants. The final spectra were obtained by three accumulations of each sample
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