Drought Resistance in Qingke Involves a Reprogramming of the Phenylpropanoid Pathway and UDP-Glucosyltransferase Regulation of Abiotic Stress Tolerance Targeting Flavonoid Biosynthesis

Tibetan hulless barley (qingke) is an important food crop in the Tibetan plateau. However, it often suffers from drought stress resulting in reduction of food production because of the extreme plateau environment. To elucidate the molecular mechanisms underlying the drought resistance of qingke, the transcriptomic and metabolomic responses of drought-sensitive (D) and drought-resistant (XL) accessions were characterized in experiments with a time course design. The phenylpropanoid pathway was reprogrammed by downregulating the lignin pathway and increasing the biosynthesis of flavonoids and anthocyanins, and this regulation improved plant tolerance for drought stress. Besides, flavonoid glycosides have induced accumulation of metabolites that participated in drought stress resistance. HVUL7H11410 exhibited the activity of wide-spectrum glucosyltransferase and mediated flavonoid glycosylation to enhance drought stress resistance. Overall, the findings provide insights into the regulatory mechanism underlying drought stress tolerance associated with metabolic reprogramming. Furthermore, the flavonoid-enriched qingke is more tolerant to drought stress and can be used as a functional food to benefit human health.