Transcriptomic Analysis of Rice (Jijing129) Reveals Growth and Gene Expression Responses to Different Red-Blue Laser Light Treatments

Artificial supplemental lighting represents a crucial agricultural technique for enhancing plant growth and development, with researchers continuously investigating the effectiveness of various light sources in horticultural applications. Laser technology, characterized by its monochromatic nature, high coherence, and elevated energy density, presents a promising light source whose potential applications and underlying mechanisms in plant supplemental lighting remain to be thoroughly explored. To investigate the effects of different red-to-blue light ratios in laser supplemental lighting on rice (<i>Oryza sativa</i> L. cv. Jijing129) seedlings, we conducted a seedling-stage lighting experiment on the rice cultivar Jijing129 in a greenhouse using an LGI-660/450 dual-wavelength semiconductor laser system. The experimental design included a natural light control (AL) and three laser treatment groups, with red: blue (R:B) ratios and corresponding photon flux densities as follows: BL (50:50; 150:150 μmol m^-2 s^-1), CL (60:40; 180:120 μmol m^-2 s^-1), and DL (75:25; 225:75 μmol m^-2 s^-1). We systematically analyzed short-term morphological, physiological, and gene expression changes to elucidate the potential mechanisms underlying yield enhancement under different laser spectra. The results indicated that, compared to AL, all laser treatments (BL, CL, and DL) significantly increased root fresh weight, dry weight, and nitrogen content in seedlings. Furthermore, the final yield was significantly improved in all laser-treated groups, with the CL treatment exhibiting the highest yield. Transcriptome sequencing identified 10,497, 10,441, 10,700, and 10,757 expressed genes in the AL, BL, CL, and DL groups, respectively. Comparative analysis revealed 101, 1645, and 2247 differentially expressed genes (DEGs) in the BL/AL, CL/AL, and DL/AL comparisons, respectively. Gene Ontology (GO) enrichment analysis showed that these DEGs were significantly enriched in pathways such as metabolic processes, nitrogen metabolism, and protein amino acid phosphorylation. Notably, genes involved in the regulation of nitrogen compound metabolism were significantly upregulated in the CL and DL treatments. Further analysis of nitrogen metabolism and photosynthesis pathways revealed that laser irradiation induced the upregulation of specific genes. Interestingly, although physiological assays showed no significant changes in CAT, SOD, and POD activities, the expression of their corresponding genes was upregulated by laser treatment, suggesting these genes play a regulatory role during the supplemental lighting process. Therefore, our results indicated that laser supplemental lighting during the rice seedling stage increased the nitrogen content in plants and modulated the expression of related genes, and these changes might have been associated with the subsequent increase in rice yield. This study lays a foundation for understanding the molecular mechanisms of laser supplemental lighting and provides empirical support for the application of laser technology as an effective light source in agriculture.