Comparison of the global metabolic responses to UV-B radiation between two medicinal Astragalus species: An integrated metabolomics strategy

Abstract

Plants employ a range of strategies in response to UV-B, including increases UV-B reflecting properties, leaf thickness, and UV-B absorbing metabolites within cell and so forth. The Chinese traditional herb Astragalus exists as two main species: Astragalus mongholicus and Astragalus membranaceus. We propose that these species employ different UV-B response strategies. In this study, A. mongholicus plants were more UV-B tolerant because they maintained a greater photosynthetic ability, higher activities of antioxidant enzymes (SOD, POD, CAT and APX) and lower levels of H2O2 under UV-B radiation. The primary metabolites and phenolic compounds each display conservative and distinct patterns that vary between the stress-adapted and non-stress-adapted Astragalus species. Changes in parts of primary metabolites represented by citric acid are conservative in both Astragalus species under UV-B radiation. The UV-B-absorbing hydroxycinnamic acid derivatives increased only in A. membranaceus, whereas myricitrin and isoflavones accumulated only in A. mongholicus. The antioxidant capability of A. mongholicus was better than that of A. membranaceus under UV-B radiation. Our results therefore showed that A. mongholicus tends to tolerate UV-B stress by mobilizing its antioxidant system and that A. membranaceus is biased to avoid UV-B stress by mobilizing UV-absorbing compounds.