Comprehensive multi-omics analysis reveals regulatory mechanisms of red and blue light combination on phenolic metabolite accumulation in larch

Larix gmelinii is a natural source of the high-value flavonoid taxifolin. However, the impact of light quality on larch growth and phenolic metabolite accumulation, particularly taxifolin, remains poorly understood. We employed LED supplemental lighting to treat two-year-old larch seedlings with red-to-blue light ratios of 1:3, 1:1, and 3:1, using white light as a control (CK). Results revealed that the 3 R:1B treatment significantly enhanced larch growth and C6C3C6 flavonoid compound accumulation, increasing taxifolin content by 48 %. Transcriptomic analysis identified significant expression changes in transcription factors, particularly ERF and NAC family members, along with PHY involved in light signaling, under 3 R:1B conditions. Key enzymes in taxifolin biosynthesis (L-phenylalanine ammonia-lyase, 4-coumarate: CoA ligase, and Chalcone isomerase) and genes like F3H and F3'5'H were markedly upregulated, driving taxifolin synthesis. This study provides a scientific basis for the cultivation of larch by regulating light quality and promoting its industrial utilization. • The red-blue light promoted the growth of larch and increased phenolic accumulation. • The growth-related transcription factor ERF and NAC are up-regulated in the 3 R:1B. • Compared with the CK, the content of taxifolin increased by 48 % in 3 R:1B. • In 3 R:1B, enhanced PAL, 4CL, and CHI enzyme activity promoted taxifolin synthesis.