Abstract
Xanthoceras sorbifolia, a medicinal and oil-rich woody plant, has great potential for biodiesel production. However, little study explores the link between gene expression level and metabolite accumulation of X. sorbifolia in response to cold stress. Herein, we performed both transcriptomic and metabolomic analyses of X. sorbifolia seedlings to investigate the regulatory mechanism of resistance to low temperature (4 °C) based on physiological profile analyses. Cold stress resulted in a significant increase in the malondialdehyde content, electrolyte leakage and activity of antioxidant enzymes. A total of 1,527 common differentially expressed genes (DEGs) were identified, of which 895 were upregulated and 632 were downregulated. Annotation of DEGs revealed that amino acid metabolism, glycolysis/gluconeogenesis, starch and sucrose metabolism, galactose metabolism, fructose and mannose metabolism, and the citrate cycle (TCA) were strongly affected by cold stress. In addition, DEGs within the plant mitogen-activated protein kinase (MAPK) signaling pathway and TF families of ERF, WRKY, NAC, MYB, and bHLH were transcriptionally activated. Through metabolomic analysis, we found 51 significantly changed metabolites, particularly with the analysis of primary metabolites, such as sugars, amino acids, and organic acids. Moreover, there is an overlap between transcript and metabolite profiles. Association analysis between key genes and altered metabolites indicated that amino acid metabolism and sugar metabolism were enhanced. A large number of specific cold-responsive genes and metabolites highlight a comprehensive regulatory mechanism, which will contribute to a deeper understanding of the highly complex regulatory program under cold stress in X. sorbifolia.
Highlights
Abiotic stresses unfavorably affect growth and productivity in plants and cause a series of changes at the morphological, physiological, biochemical, and molecular levels [1,2,3]
MDA content and electrolyte leakage (EL) value were significantly increased relative to the control, and they showed the same trend with the extension of the stress time (Fig 1A and 1B)
We found a rise in the activity of ROSscavenging enzymes, suggesting a positive response when removing reactive oxygen species (ROS) generated by cold stress in X. sorbifolia
Summary
Abiotic stresses unfavorably affect growth and productivity in plants and cause a series of changes at the morphological, physiological, biochemical, and molecular levels [1,2,3]. Low temperature (LT) is one of the major abiotic stresses in plants that disturbs physiological, cellular, metabolic, and molecular functioning, resulting in severe retardation of plant growth and development, and frequently even death [4]. During cold-stress response, plant cells tend to accumulate a series of osmoregulatory metabolites, including soluble sugars (e.g., sucrose, glucose, and galactose) and low molecular weight compounds (e.g., proline, glycine, and betaine) that enable plants to alleviate osmotic stress and maintain cell turgor, water uptake, and metabolic activity [7, 8]
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