Mechanism Of TaUGGT-B2 In Response To Abiotic Stress In Wheat

Wheat is one of the major glycophyte in the world.Its growth and yield are limited by environmental factors such as drought or saline-alkali stress.How to improve the stress tolerance and increase the yield of wheat becomes an urgent problem to be solved.ER stress is caused by unfolded or misfolded protein accumulation in endoplasmic reticulum under abiotic stress in plant cell.It was found that UDP-glucose:glycoprotein glucosyltransferase(UGGT)of maize and Arabidopsis involved in salinity or drought stress tolerance in Arabidopsis.There were 3 UGGT genes in wheat genome,out of them,the expression of TaUGGT-B was the highest.In this paper,TaUGGT-B2(TrasesCS1B02G 169900.2)overexpressed gene and VIGS knockdown line were used as materials to systematically study the role and mechanism of TaUGGT-B2 gene in response to abiotic stress.TaUGGT-B2 located in the endoplasmic reticulum and its transcriptional production was found in root,stem and leaves without obvious tissue specificity and could be induced by NaCl,alkaline and PEG.Under 200 mM NaCl,20%PEG 6000 and 100 mM carbonate alkaline(NaHCO3:Na2CO3=9:1,pH 8.9)treatments,compared with the wild type,both root length and fresh weight of the TaUGGT-B2 VIGS line were significantly reduced,indicating that TaUGGTB2 was involved in a wide range of abiotic stress tolerance.Under alkali treatment,the root length and fresh weight of the wheat TaUGGT-B2 overexpression lines were significantly increased compared with that of the wild type.The results showed that the overexpression of TaUGGT-B2 could improve the tolerance of wheat to alkali stress.Under NaCl,carbonate alkaline and PEG treatments,compared with the wild type,the expression of the unfolded protein response(UPR)marker genes in overexpression and VIGS lines were significantly up-or down-regulated accordingly,suggesting that TaUGGT-B2 may be involved in the regulation of ER stress.The total carbonyl content in VIGS line was increased significantly while the total sulfhydryl content decreased obviously,which indicated that TaUGGT-B2 could play an important role in the regulation of ER stress.The expression levels of ROS production related genes in VIGS line were significantly up-regulated,and downregulated notably in overexpression lines compared to those in wild type,conversely,the expression levels of ROS clearance related genes in VIGS line were down-regulated,and upregulated in the overexpression lines.It suggested that TaUGGT-B2 may be involved in the regulation of redox balance.Under the treatment of DTT or TUN,ROS content in the overexpression lines was significantly reduced compared with that in YM20,suggesting that ER stress induced by DTT and TUN could lead to the increase of ROS content,and the overexpression of TaUGGT-B2 in wheat could reduce the accumulation of ROS content.TaBgl-D is a potential interaction protein of TaUGGT-B2 by screening a yeast cDNA library of mixed tissues of wheat.It was also found that TaBRI1-D may be another partner of TaUGGT-B2 based on literature.The protein production of TaBgl-D(TraesCS3D02G440200)located in the endoplasmic reticulum,and that of TaBRI1-D(TraesCS3D01G246500)in the membrane.It was known that TaBRI1-D should be glycosylated in ER and then transported and localized to the cell membrane.The expression patterns of TaUGGT-B2,TaBgl-D and TaBRI1D were similar.Therefore,we inferred that TaUGGT-B2 may interact with TaBgl-D or TaBRI1D,respectively,which was then proved by assays of Y2H,LCA,BiFC.Given the interaction between TaSep15-like-B and TaUGGT-B2,and Sep15/UGGT/Bgl were important components of protein quality control system in ER,it was found that there was an interaction among them by yeast three-hybrid assay(Y3H).Collectively,it was suggested that TaUGGT-B2 was contributed to the tolerance of abiotic stress by regulating the ER stress and ROS balance.TaUGGT-B2 interacting with TaBRI1-D suggested that TaBRI1-D might be one of its glycation substrate,and the protein quality control of TaBRI1-D possibly performed by TaUGGT-B2/TaSep15-like-B/TaBgl-D complex.The results of this paper will help us to understand the basis of wheat abiotic stress tolerance and provide a useful gene for wheat stress tolerance breeding.