Transcriptome Analysis Reveals Far-Red Light's Effect on the Seedling Leaf Angle of Rice (Oryza sativa L.)

Far-red light significantly affects plant growth, including seedling development, root growth, and leaf angle, but the regulatory mechanisms underlying the positioning of the rice leaf angle remain unclear. In this study, eight light quality treatments were applied: white light (W), white light with far-red (W + Fr), red light (R), red light with far-red (R + Fr), blue light (B), blue light with far-red (B + Fr), red-blue light (RB), and red-blue light with far-red (RB + Fr). Additionally, six far-red light ratios (0%, 7.5%, 15%, 30%, 60%, 100%) were used to investigate the molecular mechanisms by which far-red light modulates leaf angles in rice seedlings. Compared to treatments without far-red light, supplemental far-red light significantly increased leaf angle and markedly decreased plant height, enhanced seedling quality, increased specific leaf weight, promoted root growth and photosynthetic capacity, and overall improved seedling performance. Moreover, far-red light markedly increased the leaf angle of rice seedlings. As the far-red proportion increased, leaf angle first increased and then decreased, a pattern consistent with the anatomical observations. Transcriptome analysis and WGCNA identified RPL5 as a key candidate gene involved in leaf angle regulation. However, the functional role of RPL5 and its regulatory mechanisms on leaf angles require further experimental validation. This study provides a theoretical basis for understanding how light and auxin signals coordinate to regulate rice leaf angles in response to far-red light.