Combination of red and blue light induces anthocyanin and other secondary metabolite biosynthesis pathways in an age-dependent manner in Batavia lettuce

Lettuce is commonly consumed around the world, spurring the cultivation of green- and red-leaf varieties in indoor farms. One common consideration for indoor cultivation is the light wavelengths/spectrum, which is an important factor for regulating growth, development, and the accumulation of metabolites. Here, we show that Batavia lettuce (Lactuca sativa cv. Batavia) grown under a combination of red (R) and blue (B) light (RB, R:B = 3:1) displayed better growth and accumulated more anthocyanin than lettuce grown under fluorescent light (FL). Anthocyanin concentration was also higher in mature stage than early stage lettuce. By performing a comparative transcriptome analysis of early and mature stage lettuce grown under RB or FL (RB or FL-lettuce), we found that RB induced the expression of genes related to oxidation-reduction reaction and secondary metabolite biosynthesis. Furthermore, plant age affected the transcriptome response to RB, as mature RB-lettuce had six times more differentially expressed genes than early RB-lettuce. Also, genes related to the accumulation of secondary metabolites such as flavonoids and anthocyanins were more induced in mature RB-lettuce. A detailed analysis of the anthocyanin biosynthesis pathway revealed key genes that were up-regulated in mature RBlettuce. Concurrently, branching pathways for flavonol and lignin precursors were down-regulated.

Automated summary

The study demonstrated that lettuce grown under a combination of red and blue light displayed better growth and accumulated more anthocyanin, with higher concentration in mature lettuce. The transcriptome response to red light was stronger in mature lettuce, inducing genes related to oxidation-reduction reaction and secondary metabolite biosynthesis. Key genes in the anthocyanin biosynthesis pathway were up-regulated in mature lettuce, while branching pathways for flavonol and lignin precursors were down-regulated.