Molecular Mechanisms Of The ?-cyclodextrin-hemin And Melatonin In Enhancing Tolerance Against Salinity In Tobacco And Maize Seedlings By Reestablishing Ion And Redox Homeostases

Recent studies have shown that ?-cyclodextrin-hemin(?-CDH)could enhance the tolerance to cadmium of alfalfa and induce cucumber adventitious root and tomato lateral root.But the ability of mitigating salt stress and the mechanism behind is still unknown.Melatonin(MT)was believed that it could promote plant growth and were involved in a variety of abiotic stresses.Up to date studies in Arabidopsis and tomato have revealed the relationship between MT and nitric oxide(NO),but whether MT could interact with other gas transmitter is unclear.Our results revealed that:1.?-CDH could mitigate the growth inhibition of tobacco caused by salt stress and preventing chlorophyll from degradation.Pretreatment with 0.1?m p-CDH could reestablish ion homeostasis in tobacco seedling cells by regulating the content of Na+,K+,Ca2+ and the K+/Na+ ratio.And it could also reduce the reactive oxygen species(ROS)content,including superoxide anion and hydrogen peroxide,to rebuild redox homeostasis via enhancing the activity of antioxidant enzymes and their expression level.Furthermore,the potency of 0.1 ?M ?CDH,in our study,was equate to 10 ?M hemin,which means that?-CDH could improve the bioavailability of hemin.2.Pretreatment with 10 ?M MT could mitigate the growth inhibition of maize aroused by salt stress.It could reestablish homeostases of ion and redox,lower the level of lipid peroxidation and guarantee the integrity of plasmalemma.To figure out the relationship between hydrogen sulfide(H2S)and MT's biological function,we carried out some related pharmacological experiments.In our study,10 ?M MT and 20?M sodium hydrosulfide(NaHS,H2S donor)had the similar relaxation effect on salt stress.And the relaxation effect of MT would be inhibited by DL-propargylglycine(PAG)which is a specific inhibitor of a key enzyme in H2S synthesis,L-cysteine desulfhydrase(L-DES).This result revealed that the salt resistance of MT might be mediated by H2S.Beyond that,we also found that MT were able to increase the expression of ZmDES,ZmOASTL1,ZmOASTL2 and the activity of L-DES,and decrease the expression of ZmATPS and ZmAPR.All these five genes were involved in H2S synthesis,by which means that MT,standing a good chance,was able to regulate the synthesis of endogenesis H2S.Taken together,our research showed that ?-CDH could mitigate the growth inhibition of tobacco under salt stress by reestablishing homeostases of ion and redox,and H2S might be involved in MT-induced maize seedlings' salinity tolerance.