Responses of endophytic microbiome and metabolome in lettuce leaves to different light quality conditions

Endophytic microbial communities and leaf metabolites dynamically respond to light quality, yet their coordinated patterns remain poorly understood in horticultural system. Here, we systematically investigated the endophytic microbial composition and metabolic profiles of lettuce leaves exposed to white (W), red (R), blue (B), and yellow (Y) light, compared with natural light (CK). Endophytic bacterial diversity increased significantly under all artificial light treatments, whereas endophytic fungal diversity decreased. At the phylum level, Actinobacteriota, Bacteroidota, and unclassified_k__Fungi were consistently enriched across W, R, B and Y groups, with Actinobacteriota showing significantly higher relative abundance than in CK. Notably, Cyanobacteria, Deinococcota, and Nitrospirota emerged as dominant phyla specifically enriched under W, B, and Y light treatments, respectively. At the genus level, Bradyrhizobium, Rothia , and Bacillus all showed increased abundance under artificial light conditions. Furthermore, Methyloversatili s, Mycobacterium, Aquabacterium, Delftia, Curvularia, Aspergillu s, and Phialosimplex served as biomarker genera characteristic of W, R, B, and Y treatments, respectively. Metabolomic analysis revealed distinct pathway enrichment and differential metabolite profiles across all light treatment relative to CK. Each spectrum uniquely modulated phenylpropanoid biosynthesis, flavonoid metabolism, and amino acid metabolism, resulting in differential accumulation of antioxidant and defense-related compounds. These findings demonstrate that light quality drives pronounced shifts in both endophytic microbial community structure and leaf metabolic profiles. The coordinated restructuring of the microbiome and metabolome provides mechanistic insights into light-dependent metabolic regulation in lettuce.