Metabolomic Analysis of Arabidopsis ost1-4 Mutant Revealed the Cold Response Regulation Mechanisms by OPEN STOMATA 1 (OST1) at Metabolic Level

Cold stress is one of the major abiotic stresses that limits the growth and development of plants. Improving the cold tolerance of plants is essential to enhance crop productivity in the changing environment. OPEN STOMATA 1 (OST1), also known as sucrose non-fermenting 1 related protein kinases 2.6/2E (SnRK2.6/SnRK2E), has been reported to involved in cold stress response in plants. This interesting protein is confined to expressed in guard cells and vascular system. However, the detailed mechanism of how OST1 regulates cold stress, especially at the metabolomic level is largely unknown. In this study, metabolomic profiling of ost1 mutant and WT Arabidopsis plants under cold stress was investigated. The results showed that ost1-4 mutants displayed cold sensitive phenotypes compared with the WT plant, as evidenced by higher MDA content and electrolyte leakage and lower photosynthetic characteristics. Next, the metabolic changes between ost1-4 and WT plants in response to cold stress was analyzed by using the GC-TOF-MS system. The results showed that numbers of metabolites were identified to be related to OST1 regulated cold stress response. A large portion of the metabolites were carbohydrates and organic acids. The KEGG enrichment analysis revealed that the alanine, aspartate and glutamate metabolism, cyanoamino acid metabolism and citrate cycle (TCA cycle) were presumptive pathways that most related to OST1 regulated cold stress response. Gene expression such as AtGDHs, AtPPC1 and AtAK1 was also in line with the metabolic changes in the presumed pathways. Overall, this study provides fundamental knowledge for understanding the underlying metabolic mechanisms of OST1 mediated cold stress response in plants.