Engineering Rice Stomata for Climate Resilience: CRISPR Strategies to Optimize Water-Use Efficiency and Drought Tolerance

Climate change is intensifying drought frequency and severity, posing a major threat to global rice (Oryza sativa) production and food security. Because stomata regulate over 90% of plant water loss while controlling CO2 uptake for photosynthesis, they represent a key target for improving water-use efficiency (WUE) and drought resilience. Advances in genome editing, particularly CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats)–Cas systems, have enabled precise manipulation of genetic networks governing stomatal development and function. In rice, stomatal development is regulated by conserved basic helix–loop–helix (bHLH) transcription factors, including OsSPCH, OsMUTE, and OsFAMA, along with their partner OsSCRM/ICE1, while EPIDERMAL PATTERNING FACTOR (EPF) and EPF-LIKE (EPFL) peptide signaling controls stomatal density and spatial patterning. These developmental pathways are further integrated with signaling modules such as the MAPK cascade and abscisic acid (ABA)-mediated guard cell regulation involving PYR/PYL/RCAR receptors and PP2Cs. CRISPR-based approaches have facilitated targeted modification of key regulatory nodes, including OsEPFL9, OsDST, OsERA1, and OsPP2Cs, enabling optimization of stomatal density, ABA sensitivity, and drought tolerance. Emerging strategies such as promoter and cis-regulatory editing, base editing, and multiplex genome editing allow quantitative tuning of stomatal traits. However, translational challenges remain, including genotype-by-environment interactions, physiological trade-offs between water conservation and photosynthesis, and the need for field-scale validation. Overall, precision engineering of stomatal development and signaling offers a promising strategy for developing climate-resilient rice varieties under variable environmental conditions.