转基因植物中抗生素抗性基因的安全性评价

20世纪80年代以来,植物转基因技术取得突飞猛进的进展。转基因植物大量出现,带来了巨大的经济效益和社会效益。与此同时,转基因植物的释放可能带来的风险也越来越受到人们的重视,抗生素抗性基因是筛选转基因植物的常用基因,其安全性引起了人们的普遍关注,作者就转基因植物中抗生素抗性基因的安全性作一综述。     

转基因植物中标记基因去除方法的研究进展

随着越来越多的转基因植物品种的出现,转基因植物的环境安全及食用安全越来越受到人们的广泛关注。目前存在的问题之一是转基因植物中抗生素或除草剂抗性的选择标记基因的存留。为了提高转基因植物的安全性,将转基因植物中选择性标记基因去除,不仅利于同一转基因植物的多次操作,而且更容易被人们所接受。就目前转基因植物中选择性标记基因去除的方法及其优缺点进行了横纵向的比较,希望对相关研究领域方法的选择方向具有指导意义。     

转基因植物中标记基因的安全性新策略

转基因植物中的除草剂和抗生素抗性标记基因潜在的生态环境和食用安全性令人担忧。解决转基因植物中抗性标记基因安全性问题有两种途径：一是转化时仍使用抗性标记基因,转基因植物再生成功后,在释放大田前将标记基因剔除;二是发展安全性标记基因用于植物遗传转化。本文综述了三种标记基因剔除系统和几种安全性标记基因在植物转化中的应用进展。     

安全标记基因在转基因植物中的应用

转基因植物的抗性标记一直是转基因生物安全性争论的焦点,是限制转基因植物应用的瓶颈之一。筛选安全标记基因替代抗生素标记基因已成为解决转基因植物安全性和促进转基因植物应用的重要策略。综述了生物安全标记基因的产生背景、系统分类、筛选原理及不同起源的标记基因在植物基因工程中的应用和存在问题。选用植物内源标记基因已成为转基因植物安全标记基因研究的重要方向。     

无标记（Marker—Free）：转基因植物研究的新趋势

目前 ,几乎所有的植物遗传转化中都要使用选择性标记基因诸如抗生素或除草剂抗性基因等来筛选转化子。为了消除由此而引起的公众的安全性顾虑 ,一种全新的发展策略即获取无选择标记的转基因植物应运而生。无选择标记的转基因植物具有许多独特的优势 ,如消除大众对转基因植物中含有选择标记基因而引起的恐惧及可以反复地向已转化的植物中叠加外源基因等 ,因此 ,这种新策略 (无标记 )有着巨大的应用潜力。本文对获得无标记转基因植物的一些途径做一综述。     

无标记(Marker-Free):转基因植物研究的新趋势

目前,几乎所有的植物遗传转化中都要使用选择性标记基因诸如抗生素或除草剂抗性基因等来筛选转化子.为了消除由此而引起的公众的安全性顾虑,一种全新的发展策略即获取无选择标记的转基因植物应运而生.无选择标记的转基因植物具有许多独特的优势,如消除大众对转基因植物中含有选择标记基因而引起的恐惧及可以反复地向已转化的植物中叠加外源基因等,因此,这种新策略(无标记)有着巨大的应用潜力.本文对获得无标记转基因植物的一些途径做一综述.     

遗传修饰工程体的生态安全性

遗传修饰工程体的生态安全性引起了人们的广泛关注。本文对转基因植物外源基因逃逸、对非靶标生物的影响、抗生素抗性基因的安全性以及生防工程菌的生态安全性等问题作了讨论。     

培育无选择标记的转基因植物

目前,几乎所有的植物遗传转化都要通过使用选择标记基因,如抗生素或除草剂抗性基因等来筛选转化子,虽然没有研究结果表明选择标记基因影响人类健康或环境安全,但近年来也引发了人们对转基因产品安全性的担心。为了消除公众对转基因食品的安全性顾虑,无选择标记的转基因植物应运而生。本文综述了共转化系统、位点特异性重组系统(包括FLP/FRT、Cre/lox、R/RS及Gin/gix系统)和转座子系统(Ac/Ds转座子系统)在培育无选择标记转基因植物中的应用。     

转基因植物检测技术的研究进展

现代植物基因工程使转基因植物及其产品越来越多地进入人们的生活,转基因植物安全性在世界范围内引起了广泛关注,对转基因植物检测技术的需求也越来越紧迫。就转基因植物检测技术的研究进展进行综述,重点介绍以基因和蛋白为目标的检测技术,包括PCR、ELISA和基因芯片技术的最新进展,并对不同方法的优缺点进行对比。此外,提出对特定代谢产物的检测是转基因植物检测的重要组成部分,是以后检测技术的发展趋势之一。最后,以差异蛋白为检测目标,结合研究工作提出基于双向电泳技术的转基因植物检测方法及其产品溯源方案。     

病程相关基因启动子片段与GUS的融合基因在拟南芥中的表达

PR1是拟南芥 (Arabidopsis thaliana L.) 系统获得抗性的一个标志基因。利用PCR技术,从拟南芥中扩增并克隆了PR1基因的启动子片段。将该启动子片段与GUS报告基因拼接,构建成含有PR1-GUS融合基因的重组表达质粒。经根癌农杆菌介导转化,得到了转基因的拟南芥植株。用已知的系统获得抗性激活剂处理转基因植物,检测到GUS活性。因此,这一转基因体系可以作为一种简便、灵敏的实验体系以筛选激活植物系统获得抗性的化合物。     

Are genetically modified plants useful and safe?

So far, plants have been genetically modified essentially to achieve resistance to herbicides, or to pathogens (mainly insects, or viruses), but resistance to abiotic stresses (such as cold, heat, drought, or salt) is also being studied. Genetically modified (GM) plants with improved nutritional qualities have more recently been developed, such as plants containing higher proportions of unsaturated fatty acids (omega-3 and omega-6) in their oil (to prevent cardio-vascular diseases), or containing beta-carotene as in the golden rice (to prevent vitamin A deficiency). Possible risks for human health (such as the production of allergenic proteins), or for the environment (such as the appearance of superweeds as a result from gene flow), should be carefully studied, and a science-based assessment of benefits vs. risks should be made on a case by case basis, both for GM plants and for plants obtained by conventional breeding methods.     

Removal of antibiotic resistance genes from transgenic tobacco plastids

Removal of antibiotic resistance genes from genetically modified (GM) crops removes the risk of their transfer to the environment or gut microbes. Integration of foreign genes into plastid DNA enhances containment in crops that inherit their plastids maternally. Efficient plastid transformation requires the aadA marker gene, which confers resistance to the antibiotics spectinomycin and streptomycin. We have exploited plastid DNA recombination and cytoplasmic sorting to remove aadA from transplastomic tobacco plants. A 4.9 kbp insert, composed of aadA flanked by bar and uidA genes, was integrated into plastid DNA and selected to remove wild-type plastid genomes. The bar gene confers tolerance to the herbicide glufosinate despite being GC-rich. Excision of aadA and uidA mediated by two 174 bp direct repeats generated aadA-free T(0) transplastomic plants containing the bar gene. Removal of aadA and bar by three 418 bp direct repeats allowed the isolation of marker-free T(2) plants containing a plastid-located uidA reporter gene.     

Gene Flow,Risk Assessment and the Environmental Release of Transgenic Plants

The release of genetically modified plants is governed by regulations that aim to provide an assessment of potential impact on the environment. One of the most important components of this risk assessment is an evaluation of the probability of gene flow. In this review, we provide an overview of the current literature on gene flow from transgenic plants, providing a framework of issues for those considering the release of a transgenic plant into the environment. For some plants gene flow from transgenic crops is well documented, and this information is discussed in detail in this review. Mechanisms of gene flow vary from plant species to plant species and range from the possibility of asexual propagation, short- or long-distance pollen dispersal mediated by insects or wind and seed dispersal. Volunteer populations of transgenic plants may occur where seed is inadvertently spread during harvest or commercial distribution. If there are wild populations related to the transgenic crop then hybridization and eventually introgression in the wild may occur, as it has for herbicide resistant transgenic oilseed rape (Brassica napus). Tools to measure the amount of gene flow, experimental data measuring the distance of pollen dispersal, and experiments measuring hybridization and seed survivability are discussed in this review. The various methods that have been proposed to prevent gene flow from genetically modified plants are also described. The current “transgenic traits” in the major crops confer resistance to herbicides and certain insects. Such traits could confer a selective advantage (an increase in fitness) in wild plant populations in some circumstances, were gene flow to occur. However, there is ample evidence that gene flow from crops to related wild species occurred before the development of transgenic crops and this should be taken into account in the risk assessment process.     

雪花莲凝集素基因（gna）的改造及其抗蚜性

用定点突变方法对编码雪花莲凝集素（Galanthus nivalis agglutinin,GNA)前体蛋白的DNA序列进行了改造和转基因烟草9Nicotana tabacum L.）抗蚜性的研究。结果表明,将GNA编码序列中含有的稀有密码子改造后,GNA的表达水平从占总可溶性蛋白的0.17％增加到0.25％,转基因烟草的抗蚜性也随之增强,从平均抑制桃蚜（Myzus per-sicae(Sulzer））虫口密度63.7％显地提高到71.0％。     

Tobacco transformants expressing antisense sequence of proline dehydrogenase gene possess tolerance to heavy metals

Analysis of resistance of genetically modified tobacco plants bearing antisense suppressor of proline dehydrogenase gene and characterized with higher content of proline to elevated concentrations of heavy metals was performed. It was demonstrated that progeny of transgenic plants have high resistance to lead, nickel and cadmium ions.     

Tobacco transformants expressing antisense sequence of proline dehydrogenase gene possess tolerance to heavy metals

Analysis of resistance of genetically modified tobacco plants bearing antisense suppressor of proline dehydrogenase gene and characterized with higher content of proline to elevated concentrations of heavy metals was performed. It was demonstrated that progeny of transgenic plants have high resistance to lead, nickel and cadmium ions.     

Field testing of virus resistant transgenic plants

A number of crop plants have been genetically modified for the purpose of resisting virus infection. Different resistance types have been observed in transgenic crops. The practical value of genetically modified, virus resistant, economically important crops can be evaluated only by field testing. The criteria for effective field resistance to viral disease can vary significantly depending on the crop and the virus. Furthermore, field testing is required to determine whether important agronomic properties of modified crops were changed by plant transformation and to confirm that the resistance observed under controlled environment is effective also under natural field conditions and to demonstrate the economical value of virus resistant, transgenic plants.     

Can tobacco have a potentially beneficial effect to our health?

With urgent pressure to clean up the contaminated environment, new approaches are needed. Phyto- and rhizoremediation using plants and related bacteria is a promising approach, but has its inborn limitations. To overcome the slow performance of the process, transgenic plants have been prepared specifically tailored for phytoremediation purposes. Our projects addressed a group of widespread synthetic organic xenobiotics, polychlorinated biphenyls (PCBs), and heavy metals as representatives of inorganic contaminants. Beside basic research studies in the field of phyto/rhizoremediation of the mentioned toxicants we focused on genetically modified plants as a highly promising tool for these purposes. We tried to prepare tobacco plants expressing the bacterial enzyme responsible for cleaving PCBs, coded by the gene bphC from the bacterial biphenyl operon. The expression of bphC product in fusion with the green fluorescent protein is described together with evaluation of the twice increased resistance of transgenic seeds towards PCBs. The other model is addressing improvement of cadmium accumulation by preparing plants bearing fused transgenes of metal binding protein (yeast metallothionein) with an introduced additional metal binding domain--polyhistidine anchor with high affinity to metals. The genetically modified plants exhibit 190% Cd accumulation of the control in harvestable parts, higher resistance and lower Cd content in roots. The performance of the plants in real contaminated soil is also evaluated.     

Evaluation of salt tolerance in Nicotiana tabacum plants bearing an antisense suppressor of the proline dehydrogenase gene

We studied the stress resistance of genetically modified (GM) tobacco plants bearing an antisense suppressor of the gene for proline dehydrogenase. Such plants are characterized by elevated proline content. The progeny of the transgenic plants were shown to have elevated salt tolerance.     

Evaluation of salt tolerance in Nicotiana tabacum plants bearing an antisense suppressor of the proline dehydrogenase gene

We studied the stress resistance of genetically modified (GM) tobacco plants bearing an antisense suppressor of the gene for proline dehydrogenase. Such plants are characterized by elevated proline content. The progeny of the transgenic plants were shown to have elevated salt tolerance.