Comparative Transcriptome Analysis Reveals the Complex Molecular Mechanisms Underlying Ultraviolet-B Tolerance in Brassica rapa var. rapa

In the agricultural areas of the Qinghai-Tibet Plateau, ultraviolet-B (UV-B) radiation varies widely. UV-B can affect the growth and development of plants. Turnip (Brassica rapa var. rapa) is an important traditional economic crop in the Qinghai-Tibet Plateau, but how turnip responds to UV-B and the complex molecular mechanisms underlying UV-B tolerance remains unclear. In this work, we found that landrace KTRG-B48b grew better and obtained a higher fresh weight of taproot in Lhasa and Kunming than landrace KTRG-B48a through common garden experiments. The phenotypic differences between the two landraces may be mechanism-based. Transcriptomes was used to analyze the differences between KTRG-B48a and KTRG-B48b. The relative expression levels of anthocyanin synthesis genes were upregulated significantly after UV-B treatment. In addition, KTRG-B48b produced less hydrogen peroxide and superoxide than KTRG-B48a. The high expression levels of anthocyanin-related genes can increase accumulation of anthocyanin, which can decrease reactive oxygen species accumulation and improved plant adaptation to the living environment of strong UV-B radiation on the Qinghai-Tibet Plateau. In this study, we proposed a model for turnip anthocyanin biosynthesis under strong UV-B radiation. Our results can provide an overview of the transcriptome response of turnip to UV-B tolerance, thus expanding our understanding the functions of anthocyanins biological in plants.