Genome-wide dissection of co-selected UV-B responsive pathways in the UV-B adaptation of qingke.

Qingke (Tibetan hulless barley) has long been cultivated and exposed to long-term and strong UV-B radiation on the Tibetan Plateau, which renders it an ideal target for elucidating novel UV-B responsive mechanisms. Here we report a comprehensive metabolite profiling and metabolite-based genome-wide association study using 196 diverse qingke and barley accessions. Our results demonstrated both constitutive and induced accumulation, and common genetic regulation, of metabolites of the different phenylpropanoid branches in UV-B protection. A total of 90 significant mGWAS loci for these metabolites were located in the barley-qingke differentiation regions and a number of high-level metabolite trait alleles were found to be significantly enriched in qingke, suggesting co-selection of various phenylpropanoids. Upon dissecting the entire phenylpropanoid pathway, we identified a number of determinants controlling natural variation of phenylpropanoid contents, including three novel proteins, a flavone C-pentosyltransferase, a tyramine hydroxycinnamoyl acyltransferase and a MYB transcription factor. Our study, furthermore, demonstrated co-selection of both constitutive and induced phenylpropanoids for UV-B protection in this species.