Metabolomics Analyses Provide Insights Into Nutritional Value and Abiotic Stress Tolerance in Halophyte Halogeton glomeratus

Exogenous Melatonin Enhances the Low Phosphorus Tolerance of Barley Roots of Different Genotypes

Melatonin (N-acetyl-5-methoxytryptamine) plays an important role in plant growth and development, and in the response to various abiotic stresses. However, its role in the responses of barley to low phosphorus (LP) stress remains largely unknown. In the present study, we investigated the root phenotypes and metabolic patterns of LP-tolerant (GN121) and LP-sensitive (GN42) barley genotypes under normal P, LP, and LP with exogenous melatonin (30 μM) conditions. We found that melatonin improved barley tolerance to LP mainly by increasing root length. Untargeted metabolomic analysis showed that metabolites such as carboxylic acids and derivatives, fatty acyls, organooxygen compounds, benzene and substituted derivatives were involved in the LP stress response of barley roots, while melatonin mainly regulated indoles and derivatives, organooxygen compounds, and glycerophospholipids to alleviate LP stress. Interestingly, exogenous melatonin showed different metabolic patterns in different genotypes of barley in response to LP stress. In GN42, exogenous melatonin mainly promotes hormone-mediated root growth and increases antioxidant capacity to cope with LP damage, while in GN121, it mainly promotes the P remobilization to supplement phosphate in roots. Our study revealed the protective mechanisms of exogenous MT in alleviating LP stress of different genotypes of barley, which can be used in the production of phosphorus-deficient crops.

Combined Proteomic and Metabolomic Analysis of the Molecular Mechanism Underlying the Response to Salt Stress during Seed Germination in Barley

Salt stress is a major abiotic stress factor affecting crop production, and understanding of the response mechanisms of seed germination to salt stress can help to improve crop tolerance and yield. The differences in regulatory pathways during germination in different salt-tolerant barley seeds are not clear. Therefore, this study investigated the responses of different salt-tolerant barley seeds during germination to salt stress at the proteomic and metabolic levels. To do so, the proteomics and metabolomics of two barley seeds with different salt tolerances were comprehensively examined. Through comparative proteomic analysis, 778 differentially expressed proteins were identified, of which 335 were upregulated and 443 were downregulated. These proteins, were mainly involved in signal transduction, propanoate metabolism, phenylpropanoid biosynthesis, plant hormones and cell wall stress. In addition, a total of 187 salt-regulated metabolites were identified in this research, which were mainly related to ABC transporters, amino acid metabolism, carbohydrate metabolism and lipid metabolism; 72 were increased and 112 were decreased. Compared with salt-sensitive materials, salt-tolerant materials responded more positively to salt stress at the protein and metabolic levels. Taken together, these results suggest that salt-tolerant germplasm may enhance resilience by repairing intracellular structures, promoting lipid metabolism and increasing osmotic metabolites. These data not only provide new ideas for how seeds respond to salt stress but also provide new directions for studying the molecular mechanisms and the metabolic homeostasis of seeds in the early stages of germination under abiotic stresses.