OsGRF1 and OsGRF2 play unequal redundant roles in regulating leaf vascular bundle formation

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Leaf shape and angle are crucial components of plant architecture and substantially influence photosynthetic efficiency and crop productivity. In this study, we found that in rice (Oryza sativa) GROWTH-REGULATING FACTORS 1 and 2 (OsGRF1 and OsGRF2) play unequally redundant roles in the regulation of leaf development. The osgrf1 mutant showed increased leaf angle, and mutations in OsGRF2 further enhanced this effect, although the leaf angle of the osgrf2 mutant remained unchanged. Cell elongation on the adaxial collar side caused an increased leaf angle. rOsGRF1 rOsGRF2 material, resistant to miR396 cleavage, had reduced leaf angles. Furthermore, due to abnormal vascular bundle development, the osgrf1 osgrf2 mutant showed narrow leaves and twisted flag leaves, which may be associated with the down-regulation of the midrib-regulating gene DROOPING LEAF (DL). OsGRF1-GFP and OsGRF2-GFP were localized in leaf primordia and young leaves, which is consistent with their roles in regulating leaf development. osgrf1 osgrf2 double mutants exhibited increased sensitivity to brassinosteroids, with RNA-seq enriching for brassinosteroid-related genes. Since OsGIF3 negatively regulates leaf angle, the OsGRF1-OsGIF3 and OsGRF2-OsGIF3 complexes influence the development of the lamina joint. Haplotype analysis showed there had been artificial selection of OsGRF1 during domestication. Our findings indicate that OsGRF1/2 negatively regulates leaf angle but positively regulates grain size, which holds promise for applications in agricultural production.