Methane enhances aluminum resistance in alfalfa seedlings by reducing aluminum accumulation and reestablishing redox homeostasis

Methane (CH 4 ) is emerging as a candidate of signal molecule recently. However, whether or how CH 4 enhances plant adaptation to aluminum (Al)-contaminated environment is still unknown. In this report, the physiological roles and possible molecular mechanisms of CH 4 in the modulation of Al toxicity in alfalfa seedlings were characterized. Our results showed that, CH 4 pretreatment could alleviate Al-induced seedling growth inhibition and redox imbalance. The defensive effects of CH 4 against Al toxicity including the remission of Al-induced root elongation inhibition, nutrient disorder, and relative electrolyte leakage. Moreover, contents of organic acids, including citrate, malate, and oxalate, were increased by CH 4 . These results were paralleled by the findings of CH 4 regulated organic acids metabolism and transport genes, citrate synthase , malate dehydrogenase , aluminum - activated malate transporter , and aluminum activated citrate transporter . Consistently, Al accumulation in seedling roots was decreased after CH 4 treatment. In addition, Al-induced oxidative stress was also alleviated by CH 4 , through the regulation of the activities of anti-oxidative enzymes, such as ascorbate peroxidase, superoxide dismutase, and peroxidase, as well as their corresponding transcripts. Our data clearly suggested that CH 4 alleviates Al toxicity by reducing Al accumulation in organic acid-dependent fashion, and reestablishing redox homeostasis.