Filament-like plant protein 7 (FPP7) negatively regulates rice salt tolerance by enhancing abscisic acid sensitivity and disturbing sodium and ROS homeostasis

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.