Leaf Morphology Genes SRL1 and RENL1 Co-Regulate Cellulose Synthesis and Affect Plant drought Tolerance

The morphological development of rice (Oryza sativa L.) leaves is closely related to plant architecture, physiological activities, and resistance. However, it is unclear whether there is a co-regulatory relationship between the morphological development of leaves and adaptation to a drought environment. In this study, a drought-sensitive, roll-enhanced, and narrow-leaf mutant (renl1) was induced by an ethyl methane sulfonate (EMS) solution from a semi-rolled leaf mutant (srl1), which was obtained from Nipponbare (NPB) through an EMS solution. Map-based cloning and functional validation showed that RENL1 encoded a cellulose synthase, with an allele of NRL1/OsCLSD4. The RENL1 mutation resulted in reductions of vascular bundles, vesicular cells, cellulose, and hemicellulose contents in cell walls, diminishing the water-holding capacity of leaves. In addition, the root system of renl1 was poorly developed and its ability to scavenge reactive oxygen species (ROS) was decreased, leading to an increase of reactive oxygen species after drought stress. Meanwhile, genetic results showed that RENL1 and SRL1 synergistically regulated cell wall components. Our results revealed a theoretical basis for further improving the molecular regulation mechanism of cellulose on rice drought tolerance, and provided a new genetic resource for enhancing the synergistic regulation network of plant type and stress resistance, thereby realizing simultaneous improvement of multiple traits in rice.