Methylglyoxal Signaling Induces The Heat Tolerance Of Maize Seedlings And Its Possible Mechanisms

With the aggravation of greenhouse effect,high temperature has become one of the important environmental stresses factors that affect crop yield and survival.Methylglyoxal(MG)is considered to be a new signal molecule at low concentration,which has been preliminarily proved to regulate many physiological processes and stress tolerance in plants.However,it is not clear whether MG can improve the heat tolerance of plants and its possible mechanism.Corn(Zea mays L.)is an important grain,feed,energy and model plant.In this paper,using maize seedlings as materials,the formation of heat tolerance induced by MG signal in maize seedlings and its relationship to antioxidant system and glyoxalase system were studied,obtaining the following results :Compared with the control without MG treatment,exogenous MG treatment significantly increased the survival rate of maize seedlings under high temperature stress,alleviated a decrease in tissue vitality,and reduced the degree of membrane damage,namely decrease in the relative conductivity,the content of malondialdehyde and the dyeing degree of evans blue under high temperature stress.These results showed that MG could improve the heat tolerance of maize seedlings.Compared with the control,exogenous MG treatment increased the activities and gene expression of peroxidase(POD),glutathione reductase(GR),catalase(CAT),monodehydroascorbate reductase(MDHAR)and glutathione S-transferase(GST);the contents of ascorbic acid(AsA),glutathione(GSH),flavonoids and carotenoids,as well as the ratio of AsA/(AsA+DHA)and GSH/(GSH+GSSG)in maize seedlings under non-stress conditions.After high temperature stress,compared with the control,MG treatment significantly increased the activities and gene expression of POD,GR,dehydroascorbic acid reductase(DHAR),MDHAR,GST,phenylalanine ammonia lyase(PAL);the concents of AsA,GSH,total phenols,flavonoids,and carotenoids;as well as AsA/(AsA+DHA)ratio in maize seedlings.It is suggested that antioxidant system plays an important role in the formation of heat tolerance induced by MG in maize seedlings.In addition,compared with the control,exogenous MG treatment increased the content of endogenous MG and the activities and gene expression of glyoxalase?(Gly?)and glyoxalase?(Gly?)in maize seedlings under non-stress conditions.Also,after high temperature stress,MG treated maize seedlings significantly maintained a higher content of endogenous MG,and the activities and gene expression of Gly?and Gly?.This indicated that the enhancement of glyoxalase system activity induced by exogenous MG was another physiological basis for the acquisition of heat tolerance induced by MG in maize seedlings.In conclusion,MG signal could improve the heat tolerance of maize seedlings,and the antioxidant system(antioxidant enzymes and non-enzyme antioxidants)and glyoxalase system(Gly? and Gly?)play an important role in the formation of heat tolerance induced by MG in maize seedlings.