OVATE family proteins (OFPs) play important roles in plant growth and development, hormone signaling, and stress response pathways. However, the functions of OsOFPs in rice are largely unknown. In this study, a novel gain-of-function rice mutant, Osofp6-D, was identified. This mutant exhibited decreased plant height, erect leaves, reduced panicle size, short and wide seeds, delayed seed germination time, and reduced fertility. These phenotypic changes were attributed to the increased expression of OsOFP6, which was caused by a T-DNA insertion. Complementation of the Osofp6-D phenotype by knockout of OsOFP6 using the CRISPR/Cas9 system confirmed that the Osofp6-D phenotype was caused by OsOFP6 overexpression. In addition, transgenic plants overexpressing OsOFP6 with the 35S promoter mimicked the Osofp6-D phenotype. Cytological observations of the glumes showed that OsOFP6 overexpression altered the grain shape, mainly by altering the cell shape. Hormone response experiments showed that OsOFP6 was involved in the gibberellin (GA) and brassinolide (BR) signaling responses. Further studies revealed that OsOFP6 interacts with E3BB, which is orthologous to the Arabidopsis central organ size-control protein BIG BROTHER (BB). This study further elucidates the regulation mechanism of the rice OFP family on plant architecture and grain shape.

Nitrogen fertilizer application rate and storage duration are critical agronomic and environmental factors affecting rice quality stability. The milling appearance, eating and nutritional quality, physicochemical properties, microstructure, and volatile metabolic profiles during long-term storage were investigated using three indica-japonica hybrid cultivars at four nitrogen fertilizer application levels. High nitrogen fertilizer application (300 kg hm⁻²) promoted an over-filled protein matrix and induced structural defects such as micropores in starch granules, which acted as “trigger points” for accelerated aging. Specifically, storage duration was the dominant factor reshaping volatile profiles and lipid degradation, but high nitrogen amplified these effects by promoting lipid oxidation and the accumulation of off-flavor compounds. Correlation analysis revealed that gel consistency (GC) is a core determinant of eating quality, exhibiting significant negative correlations with amylose content, setback, hardness and fatty acid values, while showing positive correlations with peak viscosity, breakdown value, and adhesiveness. All correlation patterns collectively contributed to the deterioration of rice eating quality after storage, indicating GC might be served as an indirect indicator for evaluating rice deterioration and applied in the breeding of rice varieties with improved storage tolerance. Microstructural analysis via SEM high nitrogen induced distinct cultivar-specific deterioration characteristics after 12 months storage.

Chalkiness is a complex quantitative trait regulated by both genetic and environmental factors. Reducing chalkiness has long been a research focus in rice genetics and breeding. A total of 108 markers on/closely linked to starch biosynthesizing genes, grain shape and chalkiness QTLs were used to detect interactions affecting chalkiness. A total of 30 and 39 marker pairs with significant bigenic epistasis were identified for percentage of grain with chalkiness (PGWC) and degree of endosperm chalkiness (DEC), respectively, of which 16 were commonly found in both traits. Using markers associated with chalkiness and marker pairs with significant epistatic effects as candidate predictors increased the coefficient of determination (R²) of the best multiple regression models for predicting both traits. GBSSI, SSIIa and the interaction between GBSSI and GBSSII were consistently identified in optimal models, indicating their critical roles in regulating rice chalkiness. R² for DEC and PGWC ranged from 36.5% to 42.7% and from 52.9% to 73.8% in two environments, respectively. PGWC decreased significantly from 38.9% to 15.10% after three cycles using marker-assisted recurrent selection (MARS). This study suggests that epistasis contributes substantially to the regulation of chalkiness, and demonstrates that MARS can effectively improve chalkiness without imposing obvious negative impacts on eating quality.