Expression of a chimeric OXR protein remodels rice architecture for enhanced grain yield by modulating redox and hormonal pathways.

Abstract

The growth-defence trade-off limits crop biotechnology because stress adaptation typically reduces productivity. We engineered and characterised OXR-Q12 (Q12), a mitochondrial chimeric protein combining the regulatory N-terminus of AtOXR1 with the catalytic TLDc domain of AtOXR2. In silico analysis predicted higher stability for Q12 than for native orthologues. Constitutive Q12 expression in Arabidopsis and rice (Oryza sativa) increased biomass, remodelled stem and vascular architecture, and enhanced grain yield. OsQ12 rice plants showed an ideal erect canopy leaf phenotype, productive tillering and a robust root system. Physiologically, Q12 conferred salinity and drought tolerance by establishing a primed basal redox state with elevated non-toxic H2O2 and an expanded glutathione content. Depleting this H2O2 pool with exogenous ascorbate selectively reverses seedling growth, salinity tolerance, and leaf erectness, indicating that this basal redox priming is a principal driver of these phenotypic adaptations. Mechanistically, our data support a model in which Q12 uncouples stress resilience from growth penalties by attenuating brassinosteroid (BR) signalling, downregulating biosynthesis (OsBRD1) and positive transcriptional regulators (OsBZR1, OsDLT and OsILI1), and differentially modulating the abscisic acid (ABA) response: the stress-protection is kept, while the side that normally brakes growth is attenuated. Q12 lines exhibit partial resistance to ABA-mediated growth and germination inhibition, yet display transcriptional hyperinduction of stress-protective marker genes (OsNCED3/4, OsDREB2A) upon salinity exposure. This redox-mediated signal may enable rapid activation of protective pathways without typical metabolic costs or growth reduction. Our results show that engineering modular OXR proteins can overcome traditional physiological trade-offs, supporting the development of high-yielding, resilient crops.

Abstract as supplied by the indexing source. © the authors / publisher.