Metabolomic Profiling of Soybeans (Glycine max L.) Reveals the Importance of Sugar and Nitrogen Metabolism under Drought and Heat Stress.

Aayudh Das,Jai Rohila,Paul Rushton

doi:10.3390/plants6020021

Abstract

Soybean is an important crop that is continually threatened by abiotic stresses, especially drought and heat stress. At molecular levels, reduced yields due to drought and heat stress can be seen as a result of alterations in metabolic homeostasis of vegetative tissues. At present an incomplete understanding of abiotic stress-associated metabolism and identification of associated metabolites remains a major gap in soybean stress research. A study with a goal to profile leaf metabolites under control conditions (28/24 °C), drought [28/24 °C, 10% volumetric water content (VWC)], and heat stress (43/35 °C) was conducted in a controlled environment. Analyses of non-targeted metabolomic data showed that in response to drought and heat stress, key metabolites (carbohydrates, amino acids, lipids, cofactors, nucleotides, peptides and secondary metabolites) were differentially accumulated in soybean leaves. The metabolites for various cellular processes, such as glycolysis, the tricarboxylic acid (TCA) cycle, the pentose phosphate pathway, and starch biosynthesis, that regulate carbohydrate metabolism, amino acid metabolism, peptide metabolism, and purine and pyrimidine biosynthesis, were found to be affected by drought as well as heat stress. Computationally based regulatory networks predicted additional compounds that address the possibility of other metabolites and metabolic pathways that could also be important for soybean under drought and heat stress conditions. Metabolomic profiling demonstrated that in soybeans, keeping up with sugar and nitrogen metabolism is of prime significance, along with phytochemical metabolism under drought and heat stress conditions.

Highlights

Environmental stresses, such as drought and heat, are serious threats to soybean cultivation in the US and in other soybean growing countries, causing multi-billion dollar losses every year
We found that sugar compounds such as ribose, deoxyribose, gluconate, xylose and xylitol are increased during drought stress; the increase is relatively lower during heat stress, which indicates that heat stress will have a greater impact on amino acid metabolism and nucleic acid biosynthesis (Figure 3 and Figure S3, and Table S2)
Metabolomic analysis of soybean leaves revealed a dynamic alteration in metabolites in response to drought and heat stress

Summary

Introduction

Environmental stresses, such as drought and heat, are serious threats to soybean cultivation in the US and in other soybean growing countries, causing multi-billion dollar losses every year. Stress in plants can arise as a reduction in growth and development that could be the result of disrupted metabolic homeostasis which requires the temporal readjustment of several metabolic pathways [1]. Under abiotic stress it is a general trend that growth and yield of crops are reduced below optimum levels [2]. Genetic and agronomic advancements have enhanced the drought tolerance of crop plants, and have resulted in stabilizing yields over time [10], but with advancements in mass spectrometry (MS) technology, it is imperative to study the global metabolomic responses of soybeans to drought and heat stresses for developing metabolomic markers, utilizing metabolic pathways, and assisting soybean breeding programs. Rabara et al [7]

Methods

Results

Conclusion