Comparative transcriptome analysis revealed distinct gene set expression associated with anthocyanin biosynthesis in response to short-wavelength light in turnip

Abstract

Short-wavelength lights (280–400 nm), such as blue and ultraviolet light, play crucial roles in anthocyanin biosynthesis in plants. Previous works have demonstrated that both blue and ultraviolet light can induce anthocyanin pigmentation in the hypocotyls of turnip seedlings. However, in this work we found that anthocyanin biosynthesis is induced either by UV-A or co-irradiation of blue and UV-B, but not by monochromatic blue or UV-B light in the peels of the swollen root of turnip (Brassica rapa L. subsp. rapa). To gain insight into regulation signaling of anthocyanin accumulation and the global transcriptional regulation induced by short-wavelength light, we investigated gene expression profiles in peels of turnip swollen root exposed to UV-A and blue + UV-B using RNA-seq. Among 41,991 genes identified by RNA-seq, 754 genes were specifically modulated by UV-A; three of these genes were anthocyanin biosynthetic structural genes: chalcone synthase, dihydroflavonol 4-reductase, and anthocyanidin synthase. By contrast, PAL, CHI and F3H, the early structural genes of the anthocyanin biosynthetic pathway were modulated by both UV-A and blue + UV-B. Gene ontology analysis manifested that non-specific signaling pathway ROS and cysteine biosynthetic process pathway were co-regulated with anthocyanin biosynthesis pathway under UV-A. This study provides a valuable overview of the transcriptome changes and gives insight into the genetic background that responsible for UV-A and blue + UV-B-induced anthocyanin biosynthesis in turnip.