Duplicated MATE Transporters OsMATE6 and OsMATE19 Additively Balance Drought Resistance and Growth in Rice (Oryza sativa L.)

Drought is a major abiotic stress limiting rice (Oryza sativa L.) production, and identifying genes that balance drought resistance with growth is a priority for molecular breeding. We previously identified the MATE transporter OsMATE6 as a negative regulator of drought resistance in rice. Here, we characterized its closest paralog, OsMATE19. OsMATE19 was predominantly expressed in roots, guard cells, and vascular tissues, and the OsMATE19–eGFP fusion protein localized to the plasma membrane. Two independent osmate19 knockout lines showed reduced leaf water loss, elevated leaf surface temperature under dehydration, improved seedling survival after PEG (polyethylene glycol)-simulated and soil drought, and 32.0–41.1% higher grain yield than the wild type under field drought conditions, without a yield penalty under irrigation. The osmate6/osmate19 double mutant showed the strongest drought resistance but, unlike either single mutant, exhibited dwarfism and significant reductions in grain yield, tiller number, plant height, and panicle architecture under normal paddy conditions. Transcriptome analysis revealed coordinated upregulation of ABA (abscisic acid)- and stress-responsive genes and repression of growth- and metabolism-related genes, with the greatest changes in the double mutant. These results reveal a dosage-dependent trade-off: disruption of either gene alone enhances drought performance without yield cost, whereas simultaneous loss of both genes over-activates stress responses at the expense of growth. Our findings provide candidate gene targets and a genetic framework for balancing drought adaptation and productivity in rice breeding.