RSD1 Is Essential for Stomatal Patterning and Files in Rice

Stomatal density is an important factor that determines the efficiency of plant gas exchange and water transpiration. Through forward genetics, we screened a mutant ( ) with decreased stomatal density and clustered stomata in rice ( ). After the first asymmetric division, some of the larger sister cells undergo an extra asymmetric division to produce a small cell neighboring guard mother cell. Some of these small cells develop into stomata, which leads to stomatal clustering, and the rest arrested or developed into pavement cell. After map-based cloning, we found the protein encoded by this gene containing DUF630 and DUF632 domains. Evolutionary analysis showed that the gene family differentiated earlier in land plants. It was found that the deletion of would lead to the disorder of gene expression regarding stomatal development, especially the expression of ( ). Through the construction of deletion mutants by CRISPR-Cas9, we found that, similar to mutants, the mutants have clustered stomata and extra small cells adjacent to the stomata. and are both required for inhibiting ectopic asymmetric cell divisions (ACDs) and clustered stomata. By dehydration stress assay, the decreased stomatal density of mutants enhanced their dehydration avoidance. This study characterized the functions of and in rice stomatal development. Our findings will be helpful in developing drought-resistant crops through controlling the stomatal density.