Construction and Identification of Site-specific Integrated and Marker-free LacS Gene Vector

The objective of this study was to solve the problem of construction a transgenic safety and site-specific integrated and marker-free LacS gene expression vector.Therefore,this experiment using plasmid pEGFP-N1 as the original framework,using PCR and restriction sites to add two with LoxP sequence at both ends of the marker genes in the pEGFP-N1 plasmid,attB sequence was added at the upstream of the multiple cloning sites for site-specific integration,then add the gene BC promoter-LacS-PolyA into the multiple cloning site.By restricted endonucleases digestion,these 3 fragments,Loxp,attB and LacS,were detected in the vector pEGFP-N1-LacS,PCR products and fragment size consistent with the expected results,the results of sequencing and oligonucleotide sequences also corresponding favorable,proved that each gene fragment was correctly connected to the corresponding position of the plasmid.In conclusion,the site-specific integrated and marker-free LacS gene vector was constructed successfully.     

Production of Transgenic Plants: More, Better, and Faster

Over the last two decades, transgenic plants have moved from being solely laboratory vehicles for basic research work to providing new varieties grown on large areas throughout the world.     

Cre/loxp系统的构建及无选择标记转基因苹果植株的获得

从‘霞晖8号’桃中克隆了一个定位于第4条染色体上的钾转运体基因PpeKUP5,该基因编码625个氨基酸,具有10个跨膜结构域;PpeKUP5主要在根部表达,其次是叶和茎中,花和果实中的表达量极低;ABA、重金属Cr和Zn处理均显著诱导其在桃幼苗各组织中的表达,其中Cr处理最为显著,高钾胁迫及重金属Cu处理显著降低了其在根部的表达水平;细菌互补试验表明PpeKUP5具有吸收外界K+（KCl或K2SO4）的功能,且在偏中性pH值条件下最为显著。本研究表明PpeKUP5是一个主导桃树根部K+吸收的钾转运体,并可能在桃树适应高钾及重金属Cr、Zn和Cu等胁迫处理和ABA 响应中起着重要作用。     

低磷条件下过表达OsPHF1基因对粳稻农艺性状的影响

【目的】 磷酸盐转运体运输协助因子(PHF1)通过转录后调节特定磷转运蛋白,影响磷酸盐的利用效率。本研究通过培育过表达OsPHF1的无选择标记转基因粳稻空育131,研究在不同磷浓度环境中OsPHF1的过表达对粳稻空育131产量的影响,为培育可商品化的磷高效转基因水稻品种提供依据。方法 利用双T-DNA方法构建OsPHF1的过表达载体,通过农杆菌侵染法和后续筛选获得了无选择标记的转基因空育131纯合株系,通过对T₃和T₄代转基因植株的田间试验,研究转基因品系在低磷浓度(75或112.5 kg/hm²过磷酸钙)、中低磷浓度(225或300 kg/hm²过磷酸钙)和正常磷浓度(450 kg/hm²过磷酸钙)下的农艺性状。结果 获得了3个无筛选标记的纯合OsPHF1过表达转基因空育131株系F18-18、F22-32和F25-6。其中,F22-32和F25-6的OsPHF1的表达量远高于野生型。大田试验显示,F22-32和F25-6株系的T₃代在中低磷(300 kg/hm²过磷酸钙)环境中,分蘖数比对照分别增加了55%和25%,增产幅度分别为38%和34%;F22-32和F25-6株系T₄代在低磷条件下(112.5 kg/hm²过磷酸钙)产量的增幅最大,增产了30%~35%;在中低磷条件下(225 kg/hm²过磷酸钙)分蘖数和产量也有明显增加。结论 双T-DNA法能用于培育过表达OsPHF1的无筛选标记转基因水稻。田间试验显示,高表达OsPHF1的转基因株系在中低磷条件下(112.5、225或300 kg/hm²过磷酸钙)分蘖数和产量稳定增加。     

低温诱导的位点特异性重组植物表达载体构建及小麦转化

选择标记基因的剔除是转基因植物商品化种植的重要基础.为建立小麦(Triticum aestivum)低温诱导的位点特异性标记基因删除体系,本研究以小麦西农928基因组DNA为模板,通过PCR扩增获得小麦低温诱导表达wcs120启动子,序列分析表明,该序列与GenBank中序列AF031235相比有一段21 bp插入,与AY493570.1序列完全一致.以含有CinH/RS2单向位点特异性重组系统的植物表达载体pXL5513为框架,成功构建了包含有抗旱相关性基因PYL5(pyrabactin-resistance like gene 5)表达框的低温诱导的位点特异性重组植物表达载体pXL5513-fwcs-RDA;并对小麦绵阳19(M19)幼胚愈伤组织进行基因枪转化,1 745块愈伤组织经筛选分化共获得9株转基因植株,经PYL5基因特异引物PCR检测,6株为阳性植株,低温春化处理后经删除引物PCR检测,6株阳性植株初步证实成功删除了选择标记基因.本研究为利用低温诱导的位点特异性重组系统进行小麦无标记基因转化奠定了基础.     

农杆菌介导的作物遗传转化研究进展

分子生物学与植物基因工程的迅速发展,使得通过基因工程手段改良作物品质、改善作物耐胁迫能力、提高作物产量成为培育作物新品种的一种有效手段.为此,综述了农杆菌介导遗传转化的分子机制、标记基因的应用、作物转化研究进展和转基因应用前景.     

无选择标记的植物表达载体的构建

以双元载体pBINPLUS为基础,在T-DNA侧翼区通过两次特异PCR、酶切和连接相结合的方法,构建了一个无标记载体pBINMF (marker-free vector)。通过酶切后测序分析,这个无标记载体在T-DNA左、右边界之间只有一个多克隆位点 (multiple cloned sites, MCS)。为了验证该载体的遗传稳定性,将gus基因克隆到该载体上并通过农杆菌介导的方法转化番茄栽培品种Moneymaker,特异PCR扩增目的基因和GUS组织染色结果表明,gus基因已经整合进入番茄基因组并得以表达。该载体为今后直接获得无标记基因、生物安全的转化体,尤其为象马铃薯、木薯等无性繁殖材料的无标记基因转化提供了可靠、有效的工具。     

Construction of Marker-Free GFP Transgenic Tobacco by Cre/Iox Site-Specific Recombination System

Marker-free GFP transgenic tobacco plants were constructed based on Cre/lox site-specific recombination system. A GFP gene was introduced into the tobacco genome using the Bar gene as a linked selectable marker flanked by recombination sites in a directed orientation. The Bar gene expression box was subsequently excised from the plant genome by a strategy of Cre gene retransformation. After removal of the Cre-NPT Ⅱ locus by genetic segregation through self-cross, plants that incorporated only the GFP transgene were obtained. Transgenic tobacco plants mediated by Agrobacterium tumefaciens were obtained, which resisted herbicide Basta and GFP expressed well, then the Cre gene was subsequently introduced into 5 plants of them, respectively, by retransformation. The leaf disks from Cre transgenic plants were used to test the resistance to Basta on the medium with 8 mg L-1 of PPT. The results showed that few discs were able to regenerate normally, and the excision at 76-100% efficiency depended on individual retransformation events. Evidence for a precise recombination event was confirmed by cloning the nucleotides sequence surrounding the lox sites of the Basta sensitive plants. The result indicated that the excision event in the recombination sites was precise and conservative, without loss or alteration of any submarginal nucleotides of the recombination sites. Bar gene excised plants were selfpollinated to allow segregation of the GFP gene from the Cre-NPT Ⅱ locus. The progenies from self-pollinated plants were scored for Kan senstivity, then the segregation of GFP gene from Cre-NPT Ⅱ locus in the Kan senstive plants were confirmed by PCR analysis subsequently. Hence, constructing marker-free transgenic tobacco plants by Cre/lox sitespecific recombination system was reliable, and the strategy presented here should be applicable to other plants for the construction of marker-free transgenic plants as well.     

一种简便的获得无标记耐盐转基因水稻植株的NaCl有效筛选浓度选择法

 以4个粳稻品种(日本晴、秀水11、武运粳7号、中花11)为材料, 研究发现,在含NaCl的NB培养基上,NaCl对水稻种子发芽的抑制率与对成熟胚愈伤组织生长的抑制率之间呈线性正相关。水稻种子发芽抑制率达50%左右时的NaCl浓度与愈伤组织生长抑制率达80%左右时的NaCl浓度一致,可以作为耐盐基因转化水稻时NaCl有效筛选浓度的重要参考。由此获得日本晴、武运粳7号和中花11 NaCl有效筛选浓度为200 mmol/L,秀水11 NaCl有效筛选浓度为250 mmol/L。采用上述浓度的NaCl对BADH基因转化的日本晴和秀水11愈伤组织进行筛选,成功获得了无标记基因的转基因水稻植株,转化率分别达到38.9%和32.0%。建立的NaCl筛选浓度确定法通过测定NaCl对水稻种子的发芽抑制率来确定水稻耐盐基因转化时合适的NaCl筛选浓度,操作简便,实验周期短,无需其他抗性标记基因。