The Abiotic Stress Tolerance Mechanism Of Wheat Sep15-like-B

Wheat is one of the main staple in the world,and is also a sweet soil crop.With the increase of population,temperature and soil salinization,wheat yield improving has become an urgent problem.Under abiotic stress,plant cell continually accumulates misfolded/unfolded protein resulting in ER stress.It was found that wheat Sep15-likeB can alleviate the ER stress in Arabidopsis under salt/osmotic stress treatment in our previous study.In this paper we studied the function and mechanism of TaSep15-likeB in response to NiSO4,NaCl or PEG6000 stress in wheat overexpression line.Li Qingqing（2017）has previously analyzed the basic characteristics of wheat TaSep15-like-B gene.It locates in the endoplasmic reticulum and expresses in roots,stems and leaves without obvious tissue specificity.TaSep15-like-B can be induced by salt or osmotic stress.TaSep15-like-B can regulate endoplasmic reticulum stress in response to salt or osmotic stress in Arabidopsis.In this study,it was found that TaSep15-like-B can also be induced by nickel.Under the stress of 75 μM and 150 μM NiSO4,the root length and leaf area of AtOE lines were significantly increased compared to wild type.The same results were obtained in TaOE lines under 200 μM NiSO4 treatment.These results showed that the overexpression of TaSep15-like-B can enhance nickel tolerance in Arabidopsis and wheat.The root length,leaf area and fresh weight of TaOE lines were significantly increased compared to wild type under 200 mM NaCl or 15%PEG treatment for 48 h,indicating that overexpression of TaSep15-like-B in wheat could improve the resistance to salt or osmotic stress.Compared to wild type,the expression of UPR marker of endoplasmic pathway in TaOE line was significantly changed under various abiotic stresses,suggesting that TaSep15-like-B may be involved in the regulation of ER stress.Under different abiotic stress treatments,the content of total carbonyl group in TaOE line was significantly lower than that in YM20,while the content of total sulfhydryl group was significantly higher than that in wild type.It indicated that TaSep15-like-B could play an important role in the regulation of ER stress.Compared to wild type,under nickel,salt or osmotic stress,the accumulation of ROS in TaOE line was significantly decreased,consistent with the corresponding significant changes in the expression of ROS production/clearance genes,suggesting that TaSep15-like-B is involved in the regulation of redox balance.It showed that ER stress could induce ROS accumulation both in wheat TaOE line and wild-type treated with dithiotreitol（DTT）and chlamycin（TUN）,and less in the former.Sep 15 homology protein in animals and maize interacts with UDP-glucose:glycoprotein glucosyltransferase（UGGT）and participates in the quality control of Nglycoprotein in ER.Eight UGGT homologous genes,which containing typical UGGT functional domains,were found in wheat genome.The physical interaction between TaSep15-like-B and TaUGGT-B2 were confirmed by yeast two-hybrid,BiFC and LCA assays.In addition,TaBgl-D was identified as one of the candidate interactor of TaSep15-like-B by Y2H screening.TaBgl-D locates in ER and is responsible for glucosyl removal in protein quality control according to literature.There was no direct interaction between them by Y2H and LCA assays.However,TaBgl-D and TaUGGTB2 may be interact with each other by bioinformatic analyses、Y2H and LCA.We suggested that TaSep15-like-B,TaUGGT-B2,and TaBgl-D may form a heterotrimer to play an important role in protein quality control.In conclusion,these results indicated that TaSep15-like-B may interact with TaBgl-D by TaUGGT-B2 in response to different abiotic stress stresses by regulating the quality control of glycoprotein in ER.These results will help us to understand the basis of wheat abiotic stress tolerance and provide a useful gene for wheat abiotic stress resistance breeding.