| Nowdays,with global warming,drought has became the dominating factors limiting plant growth and crop yield.Reactive oxygen species（ROS）are accumulated abundantly under drought stress,causing serious oxidative damage to plants.Glutathione peroxidases（GPXs）,involved in the regulation of oxidative stress,are the crucial enzymes for scavenging ROS in plants.At present,the research on plant GPX is mostly concentrated on model species,rarely on woody plants,especially mulberry（Morus alba L.）.In this study,six MaGPX genes were cloned from ‘Hong guo 2’ by RT-PCR and analyzed by bioinformatics analysis,tissue expression patterns analysis,drought stress response analysis and subcellular localization analysis.MaGPX genes were overexpressed in Arabidopsis thaliana to explore the function of response to drought stress.The main findings are as follows:1、Bioinformatics analysis indicated that the MaGPX genes had high similarity with the AtGPX genes of Arabidopsis thaliana,the typical domain of plant GPX and Cys residues,and the similar spatial structure of MaGPX protein and poplar PpGPX5,which was confirmed that the cloned sequence belonged to the GPX gene family.The predicted result of the physical and chemical properties of MaGPX protein indicated that each member was a hydrophilic protein and was a stable protein except MaGPX4.2、The qRT-PCR results showed that MaGPX1,MaGPX2,MaGPX3 and MaGPX5 were highly expressed in roots and friuts.MaGPX4 showed the high transcription levels in leaves and roots.Transcripts of MaGPX6 were mainly accumulated in fruits.The expression of MaGPX genes was induced by drought stress and the expression levels varied with treatment time and stress degree.These results suggested MaGPX might play a different role in scavenging ROS and maintaining intracellular redox balance.3、The subcellular localization results indicated that MaGPX1,MaGPX2,MaGPX3 and MaGPX6 were possibly located in the plasma membrane,cytosol and nucleus,while MaGPX4 was chloroplastic isoenzyme and MaGPX5 was potentially active in the plasma membrane,suggesting that MaGPX might have diversified function.4、The p35S::MaGPXs（pCAMIBA1301 backbone）overexpression vector was constructed to obtain overexpression of MaGPX gene in Arabidopsis thaliana.Under drought stress,the overexpressing plant OE3 and OE5 grew better than WT,APX,GR,SOD,POD and CAT enzyme activities were significantly higher than WT.O2- and H2O2 accumulation in OE3 and OE5 were lower than WT.The relative water content of OE3 and OE5 leaves was significantly higher than WT,and the water loss rate of isolated leaves was significantly lower than WT.At the same time,the water retention capacity of transgenic plants had been improved.The result above indicated overexpression of MaGPX3 and MaGPX5 enhanced the drought tolerance of transgenic plants,giving them a higher antioxidant capacity.This research revealed that the function of the MaGPX genes under drought stress,which provided theoretical support for the drought resistance research in Morus alba L. |
