Signaling molecule methylglyoxal-induced thermotolerance is partly mediated by hydrogen sulfide in maize (Zea mays L.) seedlings

Methylglyoxal (MG) was traditionally viewed as toxic by-product of glycolysis and photosynthesis in plants, but now is emerging as a signaling molecule, which, similar to hydrogen sulfide (H2S), participates in regulating seed germination, growth, development, and response to abiotic stress. However, whether exists an mutual effect between MG and H2S in improving thermotolerance in plants is not found to be reported. In this paper, interplay between MG and H2S in the formation of thermotolerance in maize seedlings was investigated. The results indicated that MG pretreatment elevated the survival percentage of maize seedlings under high-temperature stress, manifesting that MG could boost the thermotolerance of maize seedlings. Interestingly, MG-induced thermotolerance was reinforced by sodium hydrosulphide (NaHS, H2S donor), while impaired by dl-propargylglycine (inhibitor of H2S biosynthesis) and hypotaurine (scavenger of H2S), respectively. In addition, H2S could induce the thermotolerance of maize seedlings, which was impaired by aminoguanidine (AG) and N-acetyl-l-cysteine (NAC) (MG scavengers), respectively. Furthermore, MG stimulated the activity of a key enzyme in H2S biosynthesis, l-cysteine desulfhydrase, which, in turn, triggered the elevation of endogenous H2S in maize seedlings. In addition, H2S increased the level of endogenous MG; this increase was crippled by AG and NAC. This paper, for the first time, reported that MG could improve the thermotolerance of maize seedlings, and its acquisition was, at least partly, mediated by H2S.