Plasticity of OsERF109 mitigates drought stress by modulating the antioxidant defense system and morphophysiological traits in rice

• The loss of the OsERF109 gene exhibits enhanced drought tolerance and photosynthesis primarily through improved physiological water status and upregulation of ROS scavengers and osmolytes . • OsERF109 mutants showed reduced transpiration, lower canopy temperature, and better plant water status during drought stress. • Oserf109 knockouts demonstrated an enhanced root architecture, marked by a significant increase in root length (39-41%), projected area (25-27%), surface area (24-27%), number of tips (75-77%), and root volume (11-13%). • It also showed a remarkable increase in grain yield due to the increased panicle secondary branches. Freshwater shortages, exacerbated by climate change and unpredictable rainfall, significantly hinder global food security. AP2/ERF transcription factors regulate genes that help plants survive and adapt to harsh environmental stresses. Although ERF109 is linked to drought tolerance, its exact role remains unknown. To investigate this, we generated mutant alleles of the OsERF109 gene in an indica rice cultivar and studied their response to simulated drought conditions. Our findings show that the Oserf109 mutation exhibits no visible effect on plant growth and development under optimum environmental conditions. However, the Oserf109 null mutant demonstrated improved drought tolerance and survival rates. This improvement is due to reduced transpiration, lower canopy temperature, and better plant water status. The Oserf109 mutant maintains cellular hydration and membrane stability by increasing proline content under drought stress. The Oserf109 mutant also exhibits enhanced water use efficiency and improved gaseous exchange, which boosts photosynthetic efficiency, strengthens antioxidant defenses, and preserves chloroplast integrity, protecting the plant from oxidative damage during drought. Additionally, Oserf109 knockout plants showed increased tolerance to osmotic stress and reduced sensitivity to ABA, resulting in better seedling growth and higher germination rates. Our research reveals that the Oserf109 mutation enhances rice crop resilience and yield under adverse conditions. These findings illustrated the inhibitory regulatory role of OsERF109 in the drought tolerance mechanism, with the mutant form of this allele demonstrating potential implications in developing resilient rice cultivars for drought stress.