Chalcone isomerase gene (OsCHI3) increases rice drought tolerance by scavenging ROS via flavonoid and ABA metabolic pathways

The chalcone isomerase gene OsCHI , one of the key genes in the flavonoid biosynthesis pathway, plays an important role in rice ( Oryza sativa ) resistance to abiotic stresses. This study reveals how the chalcone isomerase gene family member OsCHI3 participates in rice responses to drought stress through the regulation of flavonoid biosynthesis. Overexpression of OsCHI3 increased the tolerance of rice to drought stress. In contrast, CRISPR/Cas9-mediated deletion of OsCHI3 reduced the drought tolerance of rice, an effect that is reversed by exogenous ABA treatment. Transcriptomic and physiological biochemical analyses indicated that flavonoids regulated by OsCHI3 not only scavenge reactive oxygen species (ROS) but also increase drought tolerance in rice by stimulating ABA biosynthesis through the regulation of OsNCED1 and OsABA8ox3 expression. These findings demonstrate that OsCHI3 increases drought stress tolerance in rice by activating the antioxidant defense system and the ABA metabolic pathway, providing new clues for drought-resistant rice breeding research.