转基因植物的环境生物安全：转基因逃逸及其潜在生态风险的研究和评价

转基因作物的商品化生产和大规模环境释放在带来巨大利益的同时,也引起了全球对其生物安全问题的广泛关注和争议,其中转基因通过花粉介导的基因漂移逃逸到非转基因作物及其野生近缘种,进而导致的潜在环境和生态风险就是备受争议的生物安全问题之一。转基因植物的环境生物安全涉及两方面关键问题：如何科学评价转基因植物商品化种植以后带来的环境和生态影响;如何利用环境生物安全的研究成果来制定科学有效的风险监测和管理措施。对转基因逃逸及其潜在生态风险的科学评价应包括三个重要环节：（1）检测转基因的逃逸的频率;（2）检测转基因逃逸后的表达和遗传规律;（3）确定逃逸后的转基因对野生近缘种群体适合度的影响及其进化潜力,本文将围绕对转基因逃逸及其潜在环境风险的科学评价,以转基因水稻为案例来对转基因逃逸带来生态影响的研究好评价的进展进行简要介绍,并对目前依据风险评价研究成果制定的各种管理策略进行了讨论。只有提高对转基因生物环境安全研究和评价的水平,并制定有效的风险监测和管理措施,才能为我国转基因技术的发展和转基因产品的商品化应用保驾护航。     

转基因植物根系分泌物对土壤微生态的影响

随着转基因植物商品化进程的加快,对其进行生态风险性评价日益引起学者的重视。诸如转基因逃逸到其它亲缘物种中、产生超级杂草和病毒、昆虫产生耐受性及生物多样性遭受破坏等问题已在部分转基因作物中显现。本文综述了转基因植物中根系分泌物对土壤微生态的影响。     

适合度分析对转基因逃逸潜在环境风险评价的意义北大核心CSCD

转基因作物的全球大规模种植引起了全世界的广泛关注甚至争议。经过遗传改良并具有自然选择优势的转基因作物进入商品化种植,可能将带来环境生物安全的顾虑。在这些生物安全的顾虑中,转基因通过花粉介导的基因漂移向栽培作物的野生近缘种逃逸及其导致的潜在环境风险,就是世人最为关注的环境生物安全问题之一。包括中国在内的许多国家,在转基因作物进行商品化生产之前都必须对转基因逃逸及其带来的潜在环境风险进行严格评价。按照风险评价的框架,转基因向野生近缘种逃逸及其带来潜在环境风险的评价包括3个连续的步骤:1)检测转基因漂移到作物野生近缘种的频率;2)分析转基因在野生近缘种中的表达;3)确定转基因对野生近缘种群体适合度和进化潜力的影响。大量基因漂移的研究结果已表明,转基因通过基因漂移向栽培作物邻近的野生近缘种群体逃逸难以避免,而转基因也会在作物的野生近缘种群体中正常表达。因此分析和评价转基因为野生近缘种带来的适合度效应,对于转基因逃逸及其环境风险的评价至关重要。对适合度的概念及其进化意义进行介绍,并对如何利用转基因的适合度效应分析转基因逃逸的环境风险,以及对此类环境风险进行研究和评价的具体方法予以介绍。上述知识和方法的掌握将有助于人们对转基因作物环境生物安全及其评价的全面理解。     

转基因作物的转基因技术的发展与未来

转基因作物的安全性问题在20世纪末引起全球的争论,一些人反应对转基因植物和转基因技术,本文概述了转基因植物产生的必然性,应用现状,发展趋势,引起争论的主要原因以及必须建立的安全保障,阐明对转基因作物和技术应采取的科学态度。     

转基因作物和转基因技术的发展与未来

转基因作物的安全性问题在20世纪末引起全球性的争论,一些人反对转基因植物和转基因技术.本文概述了转基因植物产生的必然性、应用现状、发展趋势、引起争论的主要原因以及必须建立的安全性保障,阐明对转基因作物和技术应采取的科学态度.     

植物“化工厂”

植物“化工厂”谢志伟（中国科学院上海生物化学研究所，上海２０００３１）关键词转基因植物，化工原材料植物转基因技术曾经被用来改良作物的性状，结合传统的育种技术培育出某些具有优良性状的作物，例如具有抗虫抗病能力的转基因植物。目前这一技术又有了新的应用，即...     

转基因的逃逸及生态风险

转基因技术的发展为提高农作物产量和解决全球人口不断增长而引发的粮食问题带来了无限的机遇,但生物技术的应用和转基因作物的环境释放也带来了一系列生物安全问题．转基因产品是否会对植物、动物、人类健康、遗传资源和环境带来危害已成为公众关注的焦点．诸多生物安全问题中最引人注目的问题之一就是转基因的逃逸及其可能导致的生态风险．文中就转基因逃逸的可能性和逃逸的不同途径、转基因逃逸后可能导致的各种生态风险、转基因逃逸的不同控制方法以及转基因作物安全距离设立应该考虑的因素等问题进行了讨论,旨在了解转基因作物的环境释放和外源基因的逃逸可能导致的生物安全问题,以及如何控制和避免转基因逃逸．     

提高转基因作物生物安全性的分子策略

随着各类转基因作物的问世及其农产品的不断上市,转基因作物的安全性问题已成为公众关心的焦点。综述了提高转基因作物生物安全性的几种分子策略,其中包括选择标记的去除,转基因的组织特异表达和诱导性表达以及转基因逃逸的控制等。     

六种作物内标准基因开发与检测研究进展

内标准基因（internal reference gene）是指能够区分物种的特异性、具有单一或恒定的低拷贝数、低变异的保守DNA序列。指定作物种类的内标准基因在转基因成分检测、物种及其产品判别等众多领域内作为鉴别其他物种的主要遗传标志,尤其是在转基因产品定量定性检测中,可用于检测样品中的物种来源以及转基因含量,对转基因产品定量定性检测具有重要意义。目前,已有多种作物的内标准基因被开发,其中玉米、油菜和水稻开发的内标准基因数量较多,但仍缺乏更为透彻的比较研究,导致选择与应用较为困难。基于此,根据国内外已有的研究成果,综述了6种检测或鉴定需求较大的作物（包括玉米、大豆、油菜、棉花、水稻和小麦）的内标准基因的研究进展,并对常见作物的内标准基因进行了系统的比较和研究,以期为植物源性、转基因成分及相关检测鉴定提供技术支撑。     

转基因植物外源基因逃逸的途径

随着转基因植物商品化进程的加快,对其进行生态风险性评价也日益引起许多学者和科学家的重视,人们对转基因逃逸到其它亲缘物种中能否产生超级杂草,昆虫是否会产生耐受性及转基因植物对生物多样性的影响等问题进行了广泛的研究,本文对转基因植物外中源基因逃逸的几种主要途径作了综述,并对研究方法与手段进行了简要讨论,希望能为有关决策和科研部门提供一些思路。     

Challenges for transgene detection in landraces and wild relatives: learning from 15 years of debate over GM maize in Mexico

Maize is one of the world’s five staple cereals and its traditional varieties constitute a global resource critical to future agricultural development. Fifteen years ago, claims that transgenes had spread into traditional landrace maize in Mexico started an international discussion on the scale and significance of transgene flow from genetically modified (GM) crops to centres of crop origin and genetic diversity. The initial discovery of transgenes in landrace maize sparked an intense environmental dispute in which the culture and traditions of indigenous people were seen as threatened by the unchecked spread of biotechnological inventions from multinational corporations. This dispute was reflected in a political and legal battle over the regulatory status of GM crops in Mexico, which continues today as approvals of GM maize for cultivation remain subject to contestation in the courts. These legal, political and environmental disputes have been fanned by the existence of a significant scientific controversy over the methods for GM detection. The use of various approaches and a lack of harmonized methods specific for monitoring and detection of transgenes in landraces has generated both positive and negative results for GM contamination in Mexico over the years. In this paper, we review the peer-reviewed literature on transgene detection in Mexican maize and highlight the challenges associated with transgene detection in landraces. In doing so, we identify the key methodological aspects under dispute and pinpoint the research bottlenecks and needs for building the capacity to effectively monitor transgene escape from GM crops to wild relatives or landraces.     

转基因逃逸及其环境生物安全评价研究进展——抗虫水稻案例分析

转基因技术研发为提高我国水稻产量和减少劳动力投入提供了巨大机遇。我国对转基因水稻研发进行了大量的投入,目前已培育了具有不同新性状的转基因水稻品系,许多品系已进入生物安全评价阶段。风险评价对转基因水稻的安全生产至关重要,是其商品化生产之前必须解决的问题,其中包括转基因逃逸及其潜在环境影响。对水稻抗虫转基因逃逸及其潜在环境风险的评价包括3个重要环节：（1）通过田间试验和模型模拟检测转基因漂移到非转基因栽培稻及其野生近缘种的频率;（2）检测转基因在栽培稻和野生近缘种后代中的表达;（3）确定转基因对野生近缘种群体适合度和进化潜力的影响。大量研究表明,在近距离的空间范围内栽培稻品种之间的基因漂移频率很低（〉0.1%）,但栽培稻与其野生近缘种的基因漂移频率变异很大。进一步研究还表明,Bt抗虫转基因在栽培稻与普通野生稻后代中均能正常表达,但在其不同生长阶段,表达量有很大变异。在有较高水平的害虫虫压下,含有抗虫转基因的栽培稻及野生近缘种杂交后代与不含转基因的对照相比,抗虫性显著提高且适合度利益明显;但是,在虫害发生水平较低时,含有抗虫转基因的群体与不含抗虫转基因的群体相比没有显著的适合度优势。综上,转基因逃逸到非转基因水稻的频率极低,并且可以通过空间隔离阻断其逃逸。虽然抗虫转基因向杂草稻以及与栽培稻距离较近的野生稻群体的逃逸无法避免,但是野生稻和杂草稻群体周围环境中的总体虫压较低,所以基因漂移带来的环境影响应十分有限。     

Letting the gene out of the bottle: the population genetics of genetically modified crops

Genetically modified (GM) plants are rapidly becoming a common feature of modern agriculture. This transition to engineered crops has been driven by a variety of potential benefits, both economic and ecological. The increase in the use of GM crops has, however, been accompanied by growing concerns regarding their potential impact on the environment. Here, we focus on the escape of transgenes from cultivation via crop x wild hybridization. We begin by reviewing the literature on natural hybridization, with particular reference to gene flow between crop plants and their wild relatives. We further show that natural selection, and not the overall rate of gene flow, is the most important factor governing the spread of favorable alleles. Hence, much of this review focuses on the likely effects of transgenes once they escape. Finally, we consider strategies for transgene containment.     

Establishment of transgenic herbicide-resistant creeping bentgrass (Agrostis stolonifera L.) in nonagronomic habitats

Concerns about genetically modified (GM) crops include transgene flow to compatible wild species and unintended ecological consequences of potential transgene introgression. However, there has been little empirical documentation of establishment and distribution of transgenic plants in wild populations. We present herein the first evidence for escape of transgenes into wild plant populations within the USA; glyphosate-resistant creeping bentgrass (Agrostis stolonifera L.) plants expressing CP4 EPSPS transgenes were found outside of cultivation area in central Oregon. Resident populations of three compatible Agrostis species were sampled in nonagronomic habitats outside the Oregon Department of Agriculture control area designated for test production of glyphosate-resistant creeping bentgrass. CP4 EPSPS protein and the corresponding transgene were found in nine A. stolonifera plants screened from 20,400 samples (0.04 +/- 0.01% SE). CP4 EPSPS-positive plants were located predominantly in mesic habitats downwind and up to 3.8 km beyond the control area perimeter; two plants were found within the USDA Crooked River National Grassland. Spatial distribution and parentage of transgenic plants (as confirmed by analyses of nuclear ITS and chloroplast matK gene trees) suggest that establishment resulted from both pollen-mediated intraspecific hybridizations and from crop seed dispersal. These results demonstrate that transgene flow from short-term production can result in establishment of transgenic plants at multi-kilometre distances from GM source fields or plants. Selective pressure from direct application or drift of glyphosate herbicide could enhance introgression of CP4 EPSPS transgenes and additional establishment. Obligatory outcrossing and vegetative spread could further contribute to persistence of CP4 EPSPS transgenes in wild Agrostis populations, both in the presence or absence of herbicide selection.     

Transgene-induced lesion mimic

Lesion mimic, i.e., the spontaneous formation of lesions resembling hypersensitive response (HR) lesions in the absence of a pathogen, is a dramatic phenotype occasionally found to accompany the expression of different, mostly unrelated, transgenes in plants. Recent studies indicated that transgene-induced lesion formation is not a simple case of necrosis, i.e., direct killing of cells by the transgene product, but results from the activation of a programmed cell death (PCD) pathway. Moreover, activation of HR-like cell death by transgene expression is viewed as an important evidence for the existence of a PCD pathway in plants. The study of lesion mimic transgenes is important to our understanding of PCD and the signals that control it in plants. PCD-inducing transgenes may provide clues regarding the different entry points into the cell death pathway, the relationships between the different branches of the pathway (e.g., developmental or environmental), or the different mechanisms involved in its induction or execution. Cell death-inducing transgenes may also be useful in biotechnology. Some lesion mimic transgenes were found to be induced in plants a state of systemic acquired resistance (SAR). These genes can be used in the development of pathogen-resistant crops. Other cell death-inducing transgenes may be used as specific cell ablation tools. Although mainly revealed unintentionally, and at times considered `an adverse phenotype', lesion mimic transgenes should not be ignored because they may prove valuable for studying PCD as well as developing useful traits in different plants and crops.     

Evaluating genetic containment strategies for transgenic plants

One of the primary concerns about genetically engineered crop plants is that they will hybridize with wild relatives, permitting the transgene to escape into the environment. The likelihood that a transgene will spread in the environment depends on its potential fitness impact. The fitness conferred by various transgenes to crop and/or wild-type hybrids has been evaluated in several species. Different strategies have been developed for reducing the probability and impact of gene flow, including physical separation from wild relatives and genetic engineering. Mathematical models and empirical experimental evidence suggest that genetic approaches have the potential to effectively prevent transgenes from incorporating into wild relatives and becoming established in wild populations that are not reproductively isolated from genetically engineered crops.     

A model to predict the frequency of integration of fitness-related QTLs from cultivated to wild soybean

With the proliferation of genetically modified (GM) products and the almost exponential growth of land use for GM crops, there is a growing need to develop quantitative approaches to estimating the risk of escape of transgenes into wild populations of crop relatives by natural hybridization. We assessed the risk of transgene escape by constructing a population genetic model based on information on fitness-related QTLs obtained from an F ₂ population of wild soybean G. soja × cultivated soybean Glycine max. Simulation started with ten F ₁ and 990 wild soybeans reproducing by selfing or outcrossing. Seed production was determined from the genetic effects of two QTLs for number of seeds (SN). Each seed survived winter according to the maternal genotype at three QTLs for winter survival (WS). We assumed that one neutral transgene was inserted at various sites and calculated its extinction rate. The presence of G. max alleles at SN and WS QTLs significantly decreased the probability of introgression of the neutral transgene at all insertion sites equally. The presence of G. max alleles at WS QTLs lowered the risk more than their presence at SN QTLs. Although most model studies have concentrated only on genotypic effects of transgenes, we show that the presence of fitness-related domestication genes has a large effect on the risk of transgene escape. Our model offers the advantage of considering the effects of both domestication genes and a transgene, and they can be widely applied to other wild × crop relative complexes.     

Transgenic trait deployment using designed nucleases

The demand for crops requiring increasingly complex combinations of transgenes poses unique challenges for transgenic trait deployment. Future value‐adding traits such as those associated with crop performance are expected to involve multiple transgenes. Random integration of transgenes not only results in unpredictable expression and potential unwanted side effects but stacking multiple, randomly integrated, independently segregating transgenes creates breeding challenges during introgression and product development. Designed nucleases enable the creation of targeted DNA double‐strand breaks at specified genomic locations whereby repair can result in targeted transgene integration leading to precise alterations in DNA sequences for plant genome editing, including the targeting of a transgene to a genomic locus that supports high‐level and stable transgene expression without interfering with resident gene function. In addition, targeted DNA integration via designed nucleases allows for the addition of transgenes into previously integrated transgenic loci to create stacked products. The currently reported frequencies of independently generated transgenic events obtained with site‐specific transgene integration without the aid of selection for targeting are very low. A modular, positive selection‐based gene targeting strategy has been developed involving cassette exchange of selectable marker genes which allows for targeted events to be preferentially selected, over multiple cycles of sequential transformation. This, combined with the demonstration of intragenomic recombination following crossing of transgenic events that contain stably integrated donor and target DNA constructs with nuclease‐expressing plants, points towards the future of trait stacking that is less dependent on high‐efficiency transformation.     

Transgene escape: what potential for crop–wild hybridization?

To date, regional surveys assessing the risk of transgene escape from GM crops have focused on records of spontaneous hybridization to infer the likelihood of crop transgene escape. However, reliable observations of spontaneous hybridization are lacking for most floras, particularly outside Europe. Here, we argue that evidence of interspecific reproductive compatibility derived from experimental crosses is an important component of risk assessment, and a useful first step especially where data from field observations are unavailable. We used this approach to assess the potential for transgene escape via hybridization for 123 widely grown temperate crops and their indigenous and naturalized relatives present in the New Zealand flora. We found that 66 crops (54%) are reproductively compatible with at least one other indigenous or naturalized species in the flora. Limited reproductive compatibility with wild relatives was evident for a further 12 crops (10%). Twenty-five crops (20%) were found to be reproductively isolated from all their wild relatives in New Zealand. For the remaining 20 crops (16%), insufficient information was available to determine levels of reproductive compatibility with wild relatives. Our approach may be useful in other regions where spontaneous crop-wild hybridization has yet to be well documented.