Non-targeted metabolomic analysis of the variations in the metabolites of two genotypes of Glycyrrhiza uralensis Fisch. under drought stress

Drought stress is one of the important abiotic stresses that restrict the growth of plants. Plants acclimatize themselves to the stress by reprogramming their metabolic pathways. Therefore, understanding the metabolic mechanisms of plants is of great importance to meet the challenge of water shortage. Licorice (Glycyrrhiza uralensis Fisch.) is a commonly used herb that is widely distributed around the world. Nevertheless, the variation of integrated metabolites in licorice under drought stress are still unclear. In this study, the non-targeted metabolomic technology was applied for the first time to comparatively investigate the metabolites changes under different degree of drought stress (slight, moderate, and intense) of two morphologically distinct genotypes of licorice from Gansu (G1) and Xinjiang (G2) provinces. Under the drought conditions, the length and dry weight of the roots of licorice were affected. Different degrees of drought caused antioxidant enzyme activities in both of the two genotypes to increase first and then decrease, and the increase in the G1 genotype was greater than that of the G2 genotype. The amino acid metabolism, flavonoid metabolism and other metabolic pathways were disrupted by drought stress. Additionally, a higher amount of amino acids such as tryptophan and tyrosine was observed in the root of the G2 genotype, and the increase of phospholipid content in the G2 genotype depended on the deepening of drought stress. Slight or moderate drought stress was beneficial to the accumulation of flavonoids. The glycosylation modification of flavonoids and accumulation patterns of jasmonic acid and abscisic acid had differences between genotypes. Collectively, this study provided new insights into the potential biochemical pathways of licorice or other legumes in response to drought and a fundamental framework to improvement the medicinal value of licorice.