Cytokinin oxidase2 deficient mutants improves panicle and grain architecture through cytokinin accumulation and enhance drought tolerance in indica rice

Abstract Cytokinins (CKs) are multifaceted hormones that regulate growth, development, and stress responses in plants. Cytokinins have been implicated in improved panicle architecture and grain yield however are inactivated by the enzyme cytokinin oxidase (CKX). In this study we developed a cytokininn oxidase2 (Osckx2) deficient mutant using CRISPR/Cas9 gene editing in indica rice and assesses its function under water deficit and salinity conditions. Loss of OsCKX2 function increased grain number, secondary panicle branching and overall grain yield through improved cytokinin content in the panicle tissue. Under drought conditions, the Osckx2 mutant conserved more water and demonstrated improved water-saving traits. Through reduced transpiration, Osckx2 mutants showed improved survival response than wild type to unset dehydration stress. Further, Osckx2maintained chloroplast and membrane integrity and showed significantly improved photosynthetic function under drought conditions through enhanced antioxidant protection systems. The OsCKX2 function negatively affects panicle grain number and drought tolerance, with no discernible impact in response to salinity. The finding suggests the utility of the beneficial Osckx2 allele in breeding to develop climate-resilient high-yielding cultivars for future food security.