Functional Study Of Maize Methionine Sulfoxide Reductase Genes ZmMSRA2 And-A5.1 In Response To Abiotic Stress Tolerance

High salinity and drought can induce excess reactive oxygen species(ROS),which could cause oxidative damage to DNA,proteins,lipids and other biological macromolecules.The sulfur-containing amino acid in protein,such as Met,is very easily oxidized by ROS to form S-methionine sulfoxide(Met-S-SO)and R-methionine sulfoxide(Met-R-SO).The methionine sulfoxide reductases(MSRs)could reduce the oxidative methionine to Met.Although MSR involved in multiple stress responses,there is no experimental evidence for the role of MSR in maize.This paper is mainly to discover the functions and their mechanisms of ZmMSRA2 and-A5.1.1 The function and mechanism of ZmMSRA2Bioinformatics analysis showed that the predicted protein ZmMSRA2 contains a highly conserved PMSR domain in C-terminus.The subcellular localization results showed that ZmMSRA2 was located in the cytosol.The results of enzyme activity assay showed that the MSR activity of the overexpressed lines were significantly higher than that of the wild one.qPCR analysis in previous study showed that the expression of ZmMSRA2 was up-regulated after NaCl and PEG treatment.Under the treatment of NaCl,Mannitol,H2O2,and ABA,the length of the main root in overexpressors was significantly increased,and the stress tolerance of the transgenic lines was stronger than that of the control.Under the osmotic stress treatment,the speed of germination in the overexpressiors were increased compared to those of the wild one.The CAT activity and proline content were measured.It was shown that CAT enzyme activity and proline content increased significantly in A.thaliana plants which constitutively expressing ZmMSRA2 than those of control.By analyzing the relevant marker genes,it was found that the expressions of ROS scavenging genes,ABA synthesis related genes,and pyrroline-5-carboxylic acid synthase gene(P5CS1)increased obviously than those in control.The above results show that maize ZmMSRA2 involved in stress tolerance via modulating proline synthesis and ROS content.2 The function and mechanism of ZmMSRA5.1Bioinformatic analysis showed that the predicted protein ZmMSRA5.1 is composed of a low complexity region at the N-terminus and a PMSR domain at the C-terminus.Subcellular localization results showed that ZmMSRA5.1 may be a secreted protein.The enzyme activity assay shown that the MSR enzyme activity in overexpressor was significantly increased compared to the control.qPCR analysis in previous work showed that the expression of ZmMSRA5.1 was up-regulated after NaCl or PEG treatment.Under NaCl,Mannitol and H2O2 treatment,the stress tolerance of the transgenic lines was significantly stronger than that of the control,and the germination rate and speed of the over-expressed seeds under salt stress were higher than that of the wild one.The CAT activity and proline content were measured.The results showed that overexpression of ZmMSRA5.1 gene in Arabidopsis promoted the CAT activity significantly in transgenic lines than in control.Through the analysis of the expression of marker genes,it was shown that the expression of ROS scavenging genes and ion channel protein related marker gene SOS3,NHX1 increased signific-antly in transgenic lines than in control.Therefore,ZmMSRA5.1 responded to abiotic stress by positively regulating ion transporter and ROS content.