Overexpression of OsPLGG1b enhances rice tolerance to high-light and high-temperature stress through modulating photorespiration.

Photorespiration, essential for photosynthetic organisms, is a highly compartmentalized pathway that relies on efficient transport of intermediates between organelles, facilitated by numerous transporters. OsPLGG1b, a glycolate/glycerate transporter localized to the chloroplast outer envelope membrane in rice, has an unclear physiological function. This study demonstrates that OsPLGG1b performs a non-redundant role distinct from OsPLGG1a. While overexpression of OsPLGG1b negatively impacted rice growth and yield under optimal conditions, likely due to disrupted carbon flux, it significantly enhanced tolerance to high-light and high-temperature (HLHT) and drought stresses. Mechanistically, OsPLGG1b-overexpressing lines exhibited elevated photorespiratory flux under HLHT stress, evidenced by increased photorespiration rates and accumulation of photorespiratory intermediates. Transcriptomic and metabolomic analyses revealed enhanced expression of photorespiratory and stress-responsive genes, as well as accumulation of protective metabolites, such as amino acids and organic acids. These adaptations enabled higher photosynthetic efficiency and photosystem II activity under HLHT stress. Collectively, these findings highlight OsPLGG1b as a promising target for improving crop resilience to environmental stress.