Methane protects against polyethylene glycol-induced osmotic stress in maize by improving sugar and ascorbic acid metabolism

Abstract

Although aerobic methane (CH 4 ) release from plants leads to an intense scientific and public controversy in the recent years, the potential functions of endogenous CH 4 production in plants are still largely unknown. Here, we reported that polyethylene glycol (PEG)-induced osmotic stress significantly increased CH 4 production and soluble sugar contents in maize (Zea mays L.) root tissues. These enhancements were more pronounced in the drought stress-tolerant cultivar Zhengdan 958 (ZD958) than in the drought stress-sensitive cultivar Zhongjiangyu No.1 (ZJY1). Exogenously applied 0.65 mM CH 4 not only increased endogenous CH 4 production, but also decreased the contents of thiobarbituric acid reactive substances. PEG-induced water deficit symptoms, such as decreased biomass and relative water contents in both root and shoot tissues, were also alleviated. These beneficial responses paralleled the increases in the contents of soluble sugar and the reduced ascorbic acid (AsA), and the ratio of AsA/dehydroascorbate (DHA). Further comparison of transcript profiles of some key enzymes in sugar and AsA metabolism suggested that CH 4 might participate in sugar signaling, which in turn increased AsA production and recycling. Together, these results suggested that CH 4 might function as a gaseous molecule that enhances osmotic stress tolerance in maize by modulating sugar and AsA metabolism.Methane (CH 4 ) is the most abundant reduced organic compound in the atmosphere, and also the second important greenhouse gas after carbon dioxide 1,2 . It was previously considered as a degradation product of organic substance by microbes under anoxic conditions 3 . Keppler et al. 4 further reported a surprising discovery that terrestrial plants can produce CH 4 under aerobic conditions. Although much controversy and debate followed this original work, a number of researchers have attempted to provide alternate explanations of the aerobic CH 4 formation from plants using different scales of measurement 5 . In fact, the non-microbial CH 4 production from plants constitutes a significant fraction of the global CH 4 sources 2,6 . A comprehensive understanding of CH 4 in plants is that the living plants and fungi can not only emit CH 4 to the atmosphere 7 , but also produce CH 4 in plants in vivo 8 . Interestingly, this phenomenon was observed in the researches of nitric oxide 9 , carbon monoxide 10 , as well as hydrogen gas 11 . In some plant species, several chemical compounds, such as lignin, cellulose, leaf surface wax, ascorbic acid (AsA), the methyl groups of sulphur-containing amino acid methionine (Met), were suggested to be the potential precursors of CH 4 2,5,12,13 .

Nitric oxide contributes to methane-induced osmotic stress tolerance in mung bean

“…Similar to the response of NO, we proved that CH 4 can alleviate salinity stress and copper stress in alfalfa plants [ 8 , 40 ]. Recently, the alleviation of osmotic stress in maize seedlings by CH 4 was confirmed, and the involvement of sugar and ascorbic acid metabolism was preliminarily elucidated [ 41 ]. However, the cross-talk between CH 4 and NO signaling in plant tolerance against osmotic stress is still elusive.…”

Research Progress on the Functions of Gasotransmitters in Plant Responses to Abiotic Stresses

“…Under osmotic stress, not only did the sugar content in maize root tissues increase by CH 4 (exogenously applied 0.65 mM), but the sugar and AsA metabolism in maize seedlings were also regulated by CH 4 [66]. Further research found a positive role of endogenous NO in CH 4 -enhanced plant tolerance against osmotic stress in mung beans [46].…”

“…Alfalfa encourages CH 4 production under salt stress [65]. Han et al [66] reported that polyethylene glycol increases CH 4 production in maize. Some researchers have demonstrated that alfalfa produces CH 4 under heavy metal stress, such as from copper (Cu) [67], aluminum (Al) [13], or cadmium (Ca) [68].…”

“…Re-establishing glutathione homeostasis, reducing lipid peroxidation [68] Alfalfa Salt reduced the activities of representative antioxidant enzymes Reducing reactive oxygen species over accumulation [65] Maize Osmotic stress decreased biomass and relative water contents Modulating sugar and AsA metabolism [66] Mung bean Osmotic stress broke the ion balance Re-establishing redox balance, alleviating seed germination inhibition [46] Zhu et al [65] found that 50% MRW reduced NaCl-induced lipid peroxidation and ROS overaccumulation in alfalfa, and ion homeostasis was re-established. In addition, MRW alleviated the NaCl-induced inhibition of seed germination and oxidative damage, partially by the upregulation of HO-1 [65].…”

Methane delays the senescence and browning in daylily buds by re‐established redox homeostasis

“…First, endogenous CH 4 is detected in maize, 23 alfalfa, 13 and Medicago sativa. 14 In this study, the endogenous levels of CH 4 in young buds significantly exceed that in the senescing condition, which implies that CH 4 may participate in the senescence process of buds.…”