Pseudotargeted Metabolomics Reveals the Effects of High Root-Zone Temperature Stress on Leaves and Roots of Medicago sativa

Abstract

Alfalfa (Medicago sativa L.) is the most widely planted forage, which have higer economically valuable and better ecological benefits in the world. However, it’s sensitive to high root-zone temperature in tropical and subtropical areas. In order to explore the changes of metabolites in alfalfa under heat stress, the study applied the unique alfalfa landrace ‘Deqin’ to explored the mechanisms on the basis of pseudotargeted metabolomics. The results showed that the phenotype of leaves and roots were changed remarkly, leaf chlorophyll content, electrolyte leakage, H2O2 content and soluble sugar also changed at different treatments. Meanwhile, heat stress may stimulate the germination of new alfalfa roots in response to adverse environment. Metabonomics analysis showed that a total of 809 and 749 metabolites were detected in leaves and roots respectively, which treated with four different ways. Of these, 343 and 383 were identified as differential metabolites in the leaves and roots, respectively; they mainly belongs to phenylpropanoids, polyketides, organic acids and derivatives, organic acids and derivatives. Among them, the differential metabolites were mainly enriched in glyoxylate and dicarboxylate metabolism, citrate cycle, aminoacyl-tRNA biosynthesis, flavone and flavonol biosynthesis, and phenylpropanoid biosynthesis. Meanwhile, some metabolites such as phenylpropanoids, polyketides, organic acids and derivatives may play an important role in response to heat stress in M. sativa ‘Deqin’. Overall, this study reports the differential metabolites and pathways in the roots and leaves of ‘Deqin’ in response to high root-zone temperature, which provides new insights into the heat stress mechanisms of alfalfa.