Dynamic Metabolic Changes in Arabidopsis Seedlings under Hypoxia Stress and Subsequent Reoxygenation Recovery

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Hypoxic stress, caused by the low cellular oxygen in the events of flooding or waterlogging, limits crop productivity in many regions of the world. Hypoxic stress in plants is often dynamic and followed by a reoxygenation process that returns the oxygen level to normal. Although metabolic responses to hypoxia have been studied in many plants, less is known about the recovery processes following stress removal. To better understand the dynamic metabolic shift from a low-oxygen environment to a reoxygenated environment, we performed time-course measurements of metabolites in Arabidopsis seedlings at 0, 6, 12, and 24 h of reoxygenation recovery after 24 h of hypoxia stress (100% N2 environment). Among the 80 metabolic features characterized using GC-MS, 60% of them were significantly changed under hypoxia. The reoxygenation phase was accompanied by progressively fewer metabolic changes. Only 26% significantly changed metabolic features by the 24 h reoxygenation. Hypoxia-induced metabolic changes returned to normal levels at different speeds. For example, hypoxia-induced accumulation of lactate decreased to a basal level after 6 h of reoxygenation, whereas hypoxia-induced accumulation of alanine and GABA showed partial recovery after 24 h of reoxygenation. Some metabolites, such as gluconate, xylose, guanine, and adenosine, constantly increased during hypoxia reoxygenation. These dynamic metabolic changes demonstrate the flexibility and complexity of plant metabolism during hypoxia stress and subsequent reoxygenation recovery.