Multiomics Analysis Revealed the Role of LsBBX22–LsHY5a/b Module in Promoting UV–B-Mediated Anthocyanin Accumulation in Lettuce

Ultraviolet-B (UV–B) radiation profoundly affects
plant
photomorphogenesis and secondary metabolism, yet its regulatory role
in lettuce (Lactuca sativa) remains
poorly understood. We conducted metabolome and transcriptome analyses
to reveal the molecular basis of UV–B adaptation in highland-grown
lettuce. Flavonoid accumulation was enhanced as a key adaptive strategy
for UV–B acclimation. The key UV–B signaling components LsHY5a/b showed positive correlations with
ten LsBBXs and flavonoid/anthocyanin-related genes.
UV–B treatment rapidly induced the transcription of LsHY5a/b and LsBBX22-1. LsBBX22-1 physically interacted with LsHY5a/b. While LsBBX22-1
activated the expression of anthocyanin-related genes, it could not
bind directly to their promoters. By contrast, LsHY5a/b directly bound
to the promoters of LsCHS1, LsCHI3, and LsF3H. Thus, LsBBX22 and LsHY5a/b acted synergistically
to regulate UV–B-induced anthocyanin biosynthesis. This study
clarified the molecular mechanism of the LsBBX22-1–LsHY5a/b
module in promoting UV–B-induced anthocyanin accumulation in
lettuce, providing a theoretical basis for cultivating high-quality
vegetables in highland regions.