The Arabidopsis Concert of Metabolic Acclimation to High Light Stress

In plants, exposure to high light irradiation induces various stress responses, which entail complex metabolic rearrangements. To systematically study such dynamic changes, we conducted time course experiments from 2 minutes to 72 hours with Arabidopsis thaliana plants exposed to high and control light conditions. We performed comparative metabolomics, transcriptomics, redox proteomics and stable isotope labelling on leaf rosettes. Our data analysis identifies a set of synchronous and successive responses that provide a deeper insight into well-orchestrated mechanisms contributing to high light acclimation. We observe a downregulation of genes encoding light harvesting proteins and a transient restriction of genes involved in linear electron flow through photosystem I. C4 acids, produced via anaplerotic routes, strongly accumulate under high light conditions. Redox homeostasis is tightly balanced by reduced NADPH production, enhanced subcellular redistribution of reducing equivalents across several subcellular compartments via photorespiration and activation of processes that quench reactive oxygen species. In this well-orchestrated network, methylerythritol 2,4-cyclodiphosphate, fulfills a dual function as intermediate of plastidic isoprenoid production and as a stress signal molecule.