玉米Ubi-1启动子在可育转基因玉米植株中的表达活性

本工作将玉米泛素基因-1启动子(Ubi-1)与大肠杆菌β-葡糖苷酸酶基因(gus,uidA)的编码区融合,通过基因枪粒子轰击方法转化来自玉米未成熟胚盾片组织的I-型愈伤组织,经PPT选择获得可育的玉米转基因植株,并采用组织化学方法分析了Ubi-1启动子驱动的gus基因在不同组织、细胞中的表达活性,发现gus基因在除花药壁以外的其它所试组织中均可以有效表达.UbiGUS在花粉、卵细胞和T1代转基因植株未成熟胚中的表达显示该启动子在植株发育的早期阶段即具有活性.对T0代转基因植株的花粉进行GUS组织化学染色,gus基因呈11分离,显示外源基因在转基因植株中以孟德尔方式遗传.同时发现,使用玉米本身的启动子Ubi-1可以降低外源基因在转基因玉米中的拷贝数,进而避免基因沉默现象的发生.目前已得到第二代转基因种子.     

玉米Ubi－1启动子在可育转基因玉米植株中的表达活性

本工作将玉米泛素基因－1启动子（Ubi-1)与大肠杆菌β－葡萄糖苷酸酶基因（gus,uidA)的编码区融合,通过基因枪粒子轰击方法转化来自水成熟胚盾片组织的I－型愈伤组织,经PPT选择获得可育的玉米转基因植株,并采用组织化学方法分析了Ubi-1启动子驱动的gus基因在不同组织,细胞中的表达活性,发现gus基因在除花药壁以外的其它所试组织中均可以有效表达。Ubi：GUS在花粉,卵细胞中T1代转基因植株未成熟胚中的表达显示该启动子在植株发育的早期阶段即具有活性。对T0代转基因植株的花粉进行GUS组织化学染色,gus基因呈1：1分离,显示外源基因在转基因植株中以孟德尔方式遗传。同时发现,使用玉米本身的启动子Ubi-1可以降低外源基因在转基因玉米中的拷贝数,进而避免基因沉默现象的发生。目前已得到第二代转基因种子。     

转基因植物中T-DNA整合的分子特征及表达

植物中不同转基因方法转化外源基因的T-DNA整合特征既具有共性,又具有特性,使得转基因的遗传在各独立转化体间呈现多样性,另外多种遗传因子和限制因素使受体植物中外源基因的表达存在下降,甚至出现基因沉默等复杂现象。本文主要对农杆菌介导及裸露DNA直接转化转基因植物中T-DNA的分子特征和转基因表达的影响因子进行了介绍和概述。转化体中转基因的遗传稳定性和表达主要取决于转基因在植物基因组中的整合位置、拷贝数及组成结构。因而,通过对具有表达水平各异的转化体进行深入的遗传分析和分子生物学研究以及转化体之间进行的比较研究,将对转基因技术自身的完善、定点整合以及更有效的利用转基因技术都具有十分重要的意义。     

转基因在玉米中的遗传分离与整合特性的研究

用ＰＣＲ和ＤＮＡ分子杂交方法研究了转基因Ｂｔ在３种不同方法获得的８个转化体后代中的遗传分离、整合性质及其稳定性,结果表明：（１）转基因在大多数转化体后中呈简单的孟德尔遗传;在Ｒ１至Ｒ２代,部分家系中转化体比例偏低,有的发生转基因丢失,但到Ｒ３代以后均趋于正常的孟德尔遗传方式,在群体中固定下来;（２）转基因在不同转化体中的整合类型有一定差异,但整合的位点和拷贝数都较少,且多呈串联或紧密连锁的整合;（     

外源基因在转基因玉米中的整合位点分析

玉米是我国第一大作物,在保障我国粮食安全中发挥重要作用。通过转基因技术培育具有抗病虫等性状的转基因玉米新品种,可有效减少产量损失。培育的转基因玉米需要鉴定外源基因整合位点,为转基因玉米的安全性评价提供重要依据。以一个抗虫转基因玉米事件IE34为材料,采用热不对称PCR(TAIL-PCR)和遗传定位方法,鉴定外源基因整合位点及旁侧序列。通过TAIL-PCR得到一段长度为776 bp的玉米基因组序列。分别在旁侧序列和外源基因上游序列设计特异性引物,建立了转基因玉米事件特异性的PCR鉴定方法。将旁侧序列在MaizeGDB中进行比对分析,发现此序列是重复序列而且存在于多条染色体上。构建转基因玉米IE34与自交系B73的F2代遗传分离群体,通过BSR-Seq方法确定外源基因整合在玉米第5染色体短臂2.32-2.70Mb区间内。通过精细定位将外源基因整合位点缩小在第5染色体2.35-2.61 Mb约260 kb的区间内。本研究结果表明,对于整合位点旁侧序列复杂的转基因事件,TAIL-PCR结合遗传定位方法能够有效鉴定外源基因的整合位点。     

人乳铁蛋白 (hLF) 转基因山羊的遗传背景分析

以随机整合方式获得的转基因动物外源基因的拷贝数、整合位点及染色体核型等遗传背景并不清楚,可能会存在外源基因的沉默整合、无效整合、毒性整合以及其表达水平不可预测等问题。文中选取了6只原代(F0)及其相对应的子一代(F1)的人乳铁蛋白(hLF)转基因山羊作为研究对象,分别颈静脉采血、提取DNA,通过染色体核型分析、实时荧光定量PCR(qPCR)、ELISA和Westernblotting等检测技术,研究其外源基因的遗传背景与表达水平。结果显示,6只F0代转基因山羊的染色体没有明显的形态变异、数量改变等异常情况。相对拷贝数高低不同(2–16),且能够稳定地遗传给下一代,F0和F1代hLF基因拷贝数一致。F1代转基因山羊表达hLF水平最高可达1.12 g/L(L3-1,拷贝数8)。结果表明,整合的外源基因能够稳定地遗传下一代,也没有对转基因山羊个体的生长发育造成障碍,而且拷贝数高低与hLF表达水平无明显的相关性,这为转基因山羊及其他转基因动物的新品种培育奠定了基础,解析了遗传背景。     

转基因玉米Bt176液相芯片检测方法的建立

为建立转基因玉米Bt176的液相芯片检测方法,根据已公布的转基因玉米Bt176外源插入基因CaMV35S启动子序列,外源基因3’端与玉米基因组DNA连接区序列,同时以玉米特异Zein内源基因序列为参照,利用Primer Premier5.0等软件设计特异性引物和探针。将探针与荧光编码微球偶联后,与PCR产物杂交反应,用液相芯片检测仪(Bio-plex 200)检测荧光信号。检测结果显示,该方法具有高特异性及灵敏度,各条探针之间无交叉反应,最低检测限可达0.01%。初步建立了检测转基因玉米Bt176的液相芯片技术,为其他转基因作物的快速高通量检测提供了借鉴和经验。     

利用微滴数字PCR方法快速分析转基因玉米中外源基因的拷贝数

以玉米自交系501幼胚为受体材料,首先将来自球形节杆菌的EPSPS基因(G23V)按玉米密码子偏爱性进行优化与人工合成,并且将其克隆到表达载体pBAC9200中;然后利用农杆菌介导法将质粒载体转入玉米自交系501的幼胚中。经过愈伤诱导、草甘膦抗性筛选和分化培养最终获得14株转化再生植株。经PCR、RT-PCR检测表明,其中5株目的基因G23V-EPSPS稳定整合且在转录水平获得表达。随后,利用微滴数字PCR技术对外源基因拷贝数进行了检测分析,分析结果表明在5株阳性转基因植株中,外源基因G23V-EPSPS拷贝数分别为0.12、1.0、0.9、1.89和0.66,介于0~2之间。成功建立了草甘膦抗性基因G23V-EPSPS在玉米中的遗传转化体系,为以新型高抗草甘膦G23V-EPSPS基因作为转基因玉米筛选标记基因奠定了基础;而且以微滴数字PCR技术代替传统的Southern Blot简便快速的完成外源基因拷贝数的分析,为微滴数字PCR技术在转基因外源基因拷贝数检测上的广泛应用做了初步的探索。     

红系特异的GFP基因在转基因小鼠中的整合和表达

应用荧光定量PCR技术对由位点控制区LCR的HS2元件和 β 珠蛋白基因启动子指导的红系特异表达绿色荧光蛋白 (GFP)基因的转基因小鼠中外源基因拷贝数进行测定 ,使用荧光显微镜和流式细胞仪检测小鼠外周血中GFP的表达水平 ,并运用荧光原位杂交技术 (FISH)确定了其中两只转基因小鼠中外源基因的整合位点 ,结果表明 :在转基因小鼠中外源基因的拷贝数各不相同且相差较大 ,而且拷贝数与GFP基因的表达量之间未呈现出相关性 ;FISH分析确定出两只转基因小鼠的外源基因整合于不同的染色体上 ;杂交信号的强弱与拷贝数的多少相一致     

抗除草剂转基因大豆插入拷贝数及其旁侧序列分析

目的:确定抗除草剂转基因大豆外源基因拷贝数和其插入位点侧翼序列.方法:采用绝对定量PCR法测定转EPSPS基因大豆中外源基因拷贝数,内参照基因标准曲线选用大豆凝集素(Lectin)基因为标准品,外源基因标准曲线以含EPSPS基因的阳性质粒为标准品.采用基因组步移技术和巢式PCR方法确定抗除草剂转基因大豆插入位点旁侧序列.结果:抗除草剂转基因大豆外源基因的拷贝数为1.CaMV35S上游扩增887bp,NOS下游扩增1 340bp.结论:明确了EPSPS外源基因在转基因大豆中为单拷贝,转基因大豆插入位点附近大豆基因组发生了DNA重排.     

Characterisation of the expression of a novel constitutive maize promoter in transgenic wheat and maize

A novel constitutive promoter from the maize histone H2Bgene was recently identified. In this study, we characterised H2B promoter activity in both wheat and maize tissues using the gusA reporter gene and two synthetic versions of the pat (phosphinothricin acetyl transferase) selectable marker gene, namely mopat and popat. Analyses of transgenic plants showed that the H2B promoter is able to drive the expression of gusA to strong, constitutive levels in wheat and maize tissues. Using an H2B:mopat construct and phosphinothricin selection, we recovered transgenic wheat plants at efficiencies ranging from 0.3% to 7.4% (mean 1.6%), and the efficiency of selection ranged from 40% to 100% (mean 77.7%). In another application, H2B was combined with the maize Ubi-1 or the maize Adh-1 intron to drive the expression of mopat and popat. Transformation efficiencies with the Ubi-1 intron were between 1.4- to 16-fold greater than with the Adh-1 intron. However, the use of either of the introns was necessary for the recovery of transgenic plants. Mopat gave higher transformation efficiencies and induced higher levels of PAT protein in maize tissues than popat.     

High frequency production of rapeseed transgenic plants via combination of microprojectile bombardment and secondary embryogenesis of microspore-derived embryos

Transgenic doubled haploid rapeseed (Brassica napus L. cvs. Global and PF₇₀₄) plants were obtained from microspore-derived embryo (MDE) hypocotyls using the microprojectile bombardment. The binary vector pCAMBIA3301 containing the gus and bar genes under control of CaMV 35S promoter was used for bombardment experiments. Transformed plantlets were selected and continuously maintained on selective medium containing 10 mg l⁻¹ phosphinothricin (PPT) and transgenic plants were obtained by selecting transformed secondary embryos. The presence, copy numbers and expression of the transgenes were confirmed by PCR, Southern blot, RT-PCR and histochemical GUS analyses. In progeny test, three out of four primary transformants for bar gene produced homozygous lines. The ploidy level of transformed plants was confirmed by flow cytometery analysis before colchicine treatment. All of the regenerated plants were haploid except one that was spontaneous diploid. High frequency of transgenic doubled haploid rapeseeds (about 15.55% for bar gene and 11.11% for gus gene) were considerably produced after colchicines treatment of the haploid plantlets. This result show a remarkable increase in production of transgenic doubled haploid rapeseed plants compared to previous studies.     

Fertile Transgenic Indica Rice Produced by Expression of Maize Ubiquitin Promoter-bar Chimaeric Gene in the Protoplasts

We report production of fertile transgenic Indica rice plants by transferring a chimaeric construct consisting of promoter, first exon and intron of maize ubiquitin gene (Ubi-1) and the coding sequences of the bar gene from Streptomyces hygroscopicus to the rice protoplasts through electroporation. In total, 11 plants were regenerated. All of them were fertile and set seeds on maturity. These plants were resistant to high concentration of PPT (400 mg l^?1) which was otherwise toxic to the untransformed controls. The gene was inherited to the progenies of the five plants in Mendelian ratio.     

Development of stem borer resistant transgenic parental lines involved in the production of hybrid rice

Stem borer resistant transgenic parental lines, involved in hybrid rice, were produced by Agrobacterium-mediated gene transfer method. Two pSB111 super-binary vectors containing modified cry1Ab/cry1Ac genes driven by maize ubiquitin promoter, and herbicide resistance gene bar driven by cauliflower mosaic virus 35S promoter were, used in this study. Embryogenic calli after co-cultivation with Agrobacterium were selected on the medium containing phosphinothricin. Southern blot analyses of primary transformants revealed the stable integration of bar, cry1Ab and cry1Ac coding sequences into the genomes of three parental lines with a predominant single copy integration and without any rearrangement of T-DNA. T1 progeny plants disclosed a monogenic pattern (3:1) of transgene segregation as confirmed by molecular analyses. Furthermore, the co-segregation of bar and cry genes in T1 progenies suggested that the transgenes are integrated at a single site in the rice genome. In different primary transformants with alien inbuilt resistance, the levels of cry proteins varied between 0.03 and 0.13% of total soluble proteins. These transgenic lines expressing insecticidal proteins afforded substantial resistance against stem borers. This is the first report of its kind dealing with the introduction of Bacillus thuringiensis (Bt) cry genes into the elite parental lines involved in the development of hybrid rice.     

Multicellular genesis of leaf primordium was demonstrated via chimaeric transgenic plant of maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.) regenerated from Type II calli

Type-II embryonic calli were induced from immature embryos of maize (Zea mays L.) genotype YD and bombarded with beta-glucuronidase gene. Bombarded calli were proliferated on normal N6 medium for 2 weeks at 26°C in the dark and selected on N6 medium containing 1 mg/l 2,4-dichlorophenoxyacetic acid (2,4-D) and 5 mg/l phosphinothricin (PPT) but without casamino acids and proline under the same conditions for 14 days. Regeneration was carried out on hormone-free MS medium containing 5 mg/l phosphinothricin at 26°C under 3000 lux illumination. Plants over 8 cm were transplanted into soil and sprayed with 250 mg/l phosphinothricin when two new leaves appeared. Except normal transgenic plants, chimaeric transgenics also were regenerated in the present work. The expression pattern of beta-glucuronidase gene in leaves of chimaeric transgenic plant revealed that more than one cell formed leaf primordium at the initial stage, and filial cells stemed from each cell in leaf primordium arranged in a row longitudinally from leaf base to leaf apex. There was a clear boundary as a straight line between the area formed by transformed cells and the area formed by normal cells. A hypothesis was put forward that the primitive cells in leaf primordium divided in a longitudinal style, resulted in leaf elongation, then the filial cells divided transversally and synchronously toward the outside to broaden the leaf.     

Agrobacterium tumefaciens mediated transfer of Phaseolus vulgaris alpha-amylase inhibitor-1 gene into mungbean Vigna radiata (L.) Wilczek using bar as selectable marker

Morphologically normal and fertile transgenic plants of mungbean with two transgenes, bar and α-amylase inhibitor, have been developed for the first time. Cotyledonary node explants were transformed by cocultivation with Agrobacterium tumefaciens strain EHA105 harboring a binary vector pKSB that carried bialaphos resistance (bar) gene and Phaseolus vulgaris α-amylase inhibitor-1 (αAI-1) gene. Green transformed shoots were regenerated and rooted on medium containing phosphinothricin (PPT). Preculture and wounding of the explants, presence of acetosyringone and PPT-based selection of transformants played significant role in enhancing transformation frequency. Presence and expression of the bar gene in primary transformants was evidenced by PCR-Southern analysis and PPT leaf paint assay, respectively. Integration of the Phaseolus vulgaris α-amylase inhibitor gene was confirmed by Southern blot analysis. PCR analysis revealed inheritance of both the transgenes in most of the T₁ lines. Tolerance to herbicide was evidenced from seed germination test and chlorophenol red assay in T₁ plants. Transgenic plants could be recovered after 8–10 weeks of cocultivation with Agrobacterium. An overall transformation frequency of 1.51% was achieved.