Inactivation of E3 Ubiquitin Ligase Encoding <i>OsDIS1</i> Improves Drought Resilience by Orchestrating Stomatal Density and Root System in Rice

Ensuring future food security necessitates the development of drought-tolerant rice cultivars for sustainable production amid climate change and declining freshwater resources. The ubiquitin-proteasome system is vital to plant stress adaptation, with RING finger proteins regulating drought responses through ubiquitination of target proteins. OsDIS1, a C3HC4 RING finger E3 ligase, has been identified as a negative regulator of drought signalling in rice. However, its precise role under complex drought conditions remains unclear. To delve further, we generated a loss-of-function Osdis1 mutant using targeted genome editing. Osdis1 mutant exhibited enhanced drought tolerance and better post-stress recovery, supported by reduced stomatal density, lower transpiration rates and maintenance of canopy temperature and CO₂ assimilation. These physiological adaptations improve water-use efficiency and delay dehydration stress without affecting photosynthesis. Improved chloroplast integrity and robust antioxidant defenses further mitigate oxidative damage, sustaining cellular homoeostasis. In addition, OsDIS1 inactivation shifted resource allocation toward roots, increasing the root-to-shoot ratio and promoting traits such as thinner roots, fewer xylem vessels, longer roots with increased surface area, thereby enhancing water foraging and drought plasticity. Comprehensively, our findings provide an inhibitory role of the mutant Osdis1 allele in drought resilience and unveil the potential for future implications in breeding drought-tolerant rice cultivars.