Dual Regulation of the Rice Yield Traits and Stress Resilience by OsHSP20: Insights from Integrative Biochemical and...

Rice (Oryza sativa L.) is a staple food crop globally, and identifying genes governing grain yield is critical for food security. Although heat shock proteins (HSPs) are known for their roles in stress tolerance, the molecular mechanisms by which they regulate yield formation remain unclear. In this study, we generated knockout and overexpression lines for OsHSP20 which is encoding a member of the Hsp20/alpha crystallin family, LOC_Os10g30162.1 (It is also one of the four candidate genes discovered during our fine mapping of major QTLs for photosynthetic rate in rice.), and performed integrated analyses combining field phenotyping, multi-stress assays, and transcriptomics. Phenotypic analyses revealed that OsHSP20 deficiency resulted in compromised plant architecture, leaf morphology, tillering, and panicle development, leading to a significant reduction in grain setting rate. Conversely, OsHSP20 overexpression enhanced drought tolerance. Mechanistically, transcriptomic and functional analyses demonstrated that OsHSP20 maintains protein homeostasis under drought stress via its chaperone activity; this function orchestrates a coordinated regulatory network involving lipid barrier formation, antioxidant defense, and carbon allocation. Our findings establish OsHSP20 as a positive regulator of both yield and drought resilience, improving crop adaptability by balancing growth and stress responses. In addition, our previous research has shown that OsHSP20 is actually one of the important components of the main QTL for rice photosynthetic rate. Therefore, this study can provide new genetic resources and a theoretical basis for cultivating rice varieties with high yield, stress resistant, and a high photosynthetic rate.