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.

Filament-like plant proteins are intermediate filament proteins that play a major role in the development and growth of plants. However, no studies have systematically identified or characterized the filament-like plant proteins (FPP) family in plants. Fifty-nine FPP candidates were found in this study by analyzing the genomes of two dicots and four monocots. Phylogenetic analysis and multicollinearity mapping showed the relatively conserved evolution of FPP genes in monocots. In rice, eight OsFPPs were characterized and found to be induced or repressed by abiotic stresses. Additional genetic evidence showed that OsFPP7-overexpressing rice exhibited increased sensitivity to abscisic acid during the germination stage, disrupted Na⁺/K⁺ homeostasis, and disrupted balance of reactive oxygen species during the seedling stage when exposed to salt stress. Conversely, the knockout of OsFPP7 alleviated abscisic acid (ABA) sensitivity, safeguarded the antioxidant system and sodium ion transport system, and thus enhanced rice salt tolerance. In the cytoskeleton, the functions of FPPs in controlling salt stress and plant stress tolerance mechanisms are all further elucidated by our findings.