Function of the auxin-responsive gene TaSAUR75 under salt and drought stress

Small auxin-upregulated RNAs(SAURs) are genes regulated by auxin and environmental factors. In this study, we identified a SAUR gene in wheat, Ta SAUR75. Under salt stress,Ta SAUR75 is downregulated in wheat roots. Subcellular localization revealed that Ta SAUR75 was localized in both the cytoplasm and nucleus. Overexpression of Ta SAUR75 increased drought and salt tolerance in Arabidopsis. Transgenic lines showed higher root length and survival rate and higher expression of some stress-responsive genes than control plants under salt and drought stress. Less H_2O_2 accumulated in transgenic lines than in control plants under drought stress. Our findings reveal a positive regulatory role of the auxin-responsive gene Ta SAUR75 in plant responses to drought and salt stress and provide a candidate gene for improvement of abiotic stress tolerance in crop breeding.

RNA-seq analysis of unintended effects in transgenic wheat overexpressing the transcription factor GmDREB1

The engineering of plants with enhanced tolerance to abiotic stresses typically involves complex multigene networks and may therefore have a greater potential to introduce unintended effects than the genetic modification for simple monogenic traits. For this reason, it is essential to study the unintended effects in transgenic plants engineered for stress tolerance. We selected drought-and salt-tolerant transgenic wheat overexpressing the transcription factor, GmDREB1, to investigate unintended pleiotropic effects using RNA-seq analysis. We compared the transcriptome alteration of transgenic plants with that of wild-type plants subjected to salt stress as a control. We found that GmDREB1 overexpression had a minimal impact on gene expression under normal conditions.GmDREB1 overexpression resulted in transcriptional reprogramming of the salt response,but many of the genes with differential expression are known to mitigate salt stress and contribute incrementally to the enhanced stress tolerance of transgenic wheat. GmDREB1 overexpression did not activate unintended gene networks with respect to gene expression in the roots of transgenic wheat. This work is important for establishing a method of detecting unintended effects of genetic engineering and the safety of such traits with the development of marketable transgenic crops in the near future.

Metabolic profiling of DREB-overexpressing transgenic wheat seeds by liquid chromatographymass spectrometry

DREBs are transcription factors that regulate abiotic stress tolerance in plants.Previously,we reported that wheat transgenic lines overexpressing Gm DREB1 showed increased tolerance to drought and salt stress.However,the molecular basis of increased tolerance is still poorly understood,and whether the overexpression of DREB will cause unexpected effects is also of concern.We performed seed metabolic profiling of the genetically modified(GM)wheat T349 and three non-GM cultivars with LC-MS to identify the metabolic basis of stress tolerance and to assess the unexpected effects of exogenous gene insertion.Although we did not note the appearance of novel metabolites or the disappearance of existing metabolites,overexpression of the transcription factor Gm DREB1 in T349 wheat influenced metabolite levels in seeds.Increased levels of stress tolerance-associated metabolites were found in the stress-sensitive non-transgenic acceptor counterpart J19,while metabolites associated with cell membrane structure and stability accumulated in T349.Among these metabolites in T349,most showed levels similar to those in the non-GM wheats.Overexpression of Gm DREB1 in T349 may cause a shift in its metabolic profile leading to down-regulation of several energy-consuming processes to favor increased yield under stress conditions,which is a reasonable expectation of breeders while creating the GM wheat and Gm DREB1 overexpression did not cause unexpected effects in T349 seeds.These results may be helpful for GM crop research and risk assessment.

基于Ni/高熵合金复合中间层调控FGH98高温合金与DD5单晶的界面互扩散行为以实现高性能连接

FGH98高温合金和DD5单晶有望在高温环境中服役.在本研究中,我们采用Ni/高熵合金(Ni/HEA)复合中间层实现了FGH98与DD5的高性能扩散连接.FGH98高温合金、DD5单晶和Ni/HEA复合中间层间元素互扩散导致焊缝处形成细小Ni3Al相(γ′)增强FCC固溶体的复合组织,实现了高强度界面结合.温度是影响界面元素扩散的关键参量.当焊接温度从1075℃提高至1130℃时,界面处元素扩散剧烈,促进了界面空隙闭合和复合扩散区增厚,有利于接头性能提升.然而,过高的扩散温度(1160℃)导致FGH98高温合金和HEA层中形成粗晶组织及化合物相,使接头性能恶化.FGH98-DD5连接体系最优工艺参数为:焊接温度为1130℃、焊接压力为2 MPa、焊接时间为1 h.接头最高抗剪强度为650 MPa,剪切过程中接头表现为韧性断裂.该研究可为界面元素扩散调控提供科学借鉴,也为FGH98高温合金与DD5单晶的可靠连接提供了理论和技术支持.

Microstructure and mechanical properties of transient liquid phase bonding DD5 single-crystal superalloy to CrCoNi-based medium-entropy alloy

This study focuses on the transient liquid phase(TLP)bonding of DD5 single-crystal superalloy to Cr Co Nibased medium-entropy alloy(MEA)using a BNi-2 filler alloy.The microstructure and mechanical properties of the TLP-bonded DD5/MEA joint were evaluated,and the microstructural evolution mechanism was investigated.The formation of the isothermal solidification zone(ISZ)depended on the diffusion of the melting-point depressants(Si and B elements)from the liquid filler into the DD5 and MEA substrates,as well as the dissolution of the substrates.Boron diffused along theγchannel of DD5 and reacted to form M_(5)B_(3)boride,herein referred to as the diffusion-affected zone(DAZ I).Similarly,the Cr_(5)B_(3)boride precipitated in the Ni-rich MEA matrix adjacent to the MEA substrate(i.e.,DAZ II).Additionally,a coherent orientation of[0]_(BCY)//[011]_(FCC)and(002)_(BCY)//(200)_(FCC)was detected between M_(5)B_(3)boride with a body-centered tetragonal(BCT)structure and the face-centered cubic(FCC)matrix.The performance of the joint was dominated by the properties of the bonding seam.As the bonding time increased from 20to 80 min,the athermal solidification zone(including eutectic microstructure)was gradually replaced by the ISZ exhibiting excellent plastic deformation capability,and the shear strength of the joint was improved.The maximum shear strength(752 MPa)was achieved when the eutectic-free joint was bonded at 1050℃ for 80 min.The fracture morphology revealed a mixture mode,indicating the initiation of cracks in the DAZ II,mainly propagating in the ISZ,and passing through the DAZ I.