植物遗传转化的替代方法及研究进展

农杆菌介导法和基因枪法是两种目前应用最广泛和最可靠的植物遗传转化方法.由于其存在一些不足,因此,需要探索可替代它们的其他植物遗传转化方法以弥补农杆菌介导法和基因枪法的缺点,使其更加适用于特定目标植物的转化事件中,转化效率也随之提高.对这些可替代的遗传转化方法进行概述,并简要介绍各种方法的优缺点及其在农作物转化中的应用情况.     

类固醇雌激素在土壤-植物体系中的迁移转化及其毒理效应

类固醇雌激素(steroidal estrogens, SEs)作为典型的内分泌干扰物,在环境介质中被广泛检出,其进入生物体后可模拟细胞内源性激素作用对生物体生长、发育、生殖等产生不利影响,因此越来越引起关注。目前关于SEs的研究报道多集中于粪便、土壤、水体等介质中的检出及环境行为,以及SEs在水生生物体内的迁移和转化,其累积效应及其机制研究较为系统和全面。相较而言,SEs在土壤-植物体系中的迁移累积报道较少,但是对于掌握农田系统中SEs迁移转化的需求更为迫切。结合现有的国内外相关研究,总结了SEs在土壤-植物体系中的吸收累积和迁移转化行为特征,概述了植物吸收代谢SEs的影响因素以及SEs对植物生长发育的毒理效应。目前针对SEs的植物体吸收大多数仍基于室内模拟实验,对于其在土壤-植物多相态体系中迁移转化机理尚不清楚。因此,对今后的研究方向提出以下几点建议:(1)除室内模拟实验外,对实际土壤-植物系统中的研究更具价值,特别是SEs土壤-土壤水-植物多相态体系中的迁移转化等过程;(2)应结合SEs的来源,探究畜禽粪便、城市污泥及污水等不同源SEs对植物吸收、累积污染物的影响及污染风险;(3)加强对农作物体内SEs残留的监测和风险评估,制定SEs农作物检出及人体摄入的相关标准。     

主要农作物转基因研究现状和展望

近15年来,大豆、水稻、玉米、小麦等主要农作物转基因研究取得了较大进展,几乎各种遗传转化方法在这些作物上都取得了成功,尤其是农杆菌介导法,不仅在难转化的双子叶作物大豆上取得了成功,而且在单子叶作物水稻、玉米、小麦上先后取得了突破。同时,将一些与重要性状改良有关的外源基因转入了主要农作物,包括抗虫、抗病、抗除草剂、抗逆、品质改良、发育调控、营养吸收等。转基因大豆、玉米、棉花、油菜在生产上得到了大面积种植,产生了极大的经济效益,2004年全球转基因作物的种植面积达到了8100万公顷。本文对大豆、玉米、水稻和小麦等主要农作物转基因研究历史和产业化现状进行了综述,并对主要农作物转基因研究中存在的问题进行了分析。     

T-DNA转移研究进展

植物遗传转化技术近年在农作物性状改良、植物生物反应器利用以及基因功能鉴定等方面得到了广泛的应用.T-DNA转移是植物细胞农杆菌介导遗传转化整合和表达外源基因的基础.农杆菌Ti质粒vir基因编码蛋白、农杆菌一些染色体基因编码蛋白及植物细胞一些基因编码蛋白或因子均参与T-DNA转移.转移过程包括农杆菌对植物细胞的识别、附着,细菌对植物信号物质的感受,细菌vir基因的诱导表达,T复合体的形成,跨膜运输,进核运输和整合等一序列过程.植物细胞因子与农杆菌T-DNA转移相关蛋白的相互作用最近被认为在T-DNA转移过程中起重要作用.     

农杆菌介导的植物遗传转化进展

农杆菌介导的植物遗传转化进展.李子银＠胡会庆.华中农业大学作物遗传改良国家重点实验室农杆菌介导的植物遗传转化进展李子银胡会庆（华中农业大学作物遗传改良国家重点实验室武汉４３００７０）根癌农杆菌（Ａｇｒｏｂａｃｔｅｒｉｕｍｔｕｍｅｆａｃｉｅｎｓ）和发根农杆菌（Ａｇｒｏｂａｃｔｅｒｉｕｍｒｈｉｚｏｇｅｎｅｓ）是两种寄主非常广泛的土壤细菌,在自然状态下它们能通过伤口侵染植物,分别导致冠瘿瘤和毛...     

植物根系响应低磷胁迫的机理研究

磷是植物生长的必需营养元素之一。但大部分土壤中有效磷含量较低,难以满足植物生长的需求。作物磷效率遗传改良是解决土壤磷供应不足的有效途径。根系是植物吸收矿质营养元素的主要器官,其性状决定了植物对土壤磷的吸收利用效率。解析根系对低磷胁迫的响应机制是进行作物磷效率遗传改良的基础。主要介绍了近年来关于植物根系响应低磷胁迫机理的重要研究成果。     

促进植物高效遗传转化的发育调节因子及其在玉米中的应用进展*

高效遗传转化技术体系的建立对植物功能基因组学研究和作物新品种的培育均具有促进作用,目前,再生效率低下是限制许多植物高效遗传转化体系建立的主要技术屏障之一。随着对植物分生组织和体细胞胚形成过程研究的深入,鉴定到了一些关键调控基因,统称为发育调节因子。发育调节因子应用于植物遗传转化后,可以有效改善植物分生组织诱导和再生能力,为提高遗传转化效率提供了重要机遇。综述了7类发育调节因子在提高植物遗传转化效率中的研究进展,重点介绍了其中3类在促进玉米遗传转化中的应用,最后展望了建立植物高效遗传转化体系的发展方向。     

广州市农作物系统与大气的CO2交换

在广泛收集资料和实验分析的基础上,研究了广州市各种农作物系统与大气CO2交换.分析了各种农作物系统净生产力吸收CO2的能力和碳汇功能大小.结果表明:2005年广州市8种农作物系统作物净生产力吸收CO2 4 032 366t·a-1,其土壤CO2排放3981753t·a-1,吸收大于排放,对大气CO2而言,整个农作物系统是一个弱的碳汇;水稻、甘蔗、木薯和果用瓜4种连作或高杆作物系统每年作物净生产力吸收CO2量大于土壤CO2的排放量,系统具有较大的碳汇功能,花生、大豆、花卉和蔬菜4种矮杆作物系统每年作物净生产力吸收CO2量小于土壤CO2的排放量,系统起着碳源作用;果实或经济产量生长在地上部分的作物其单位面积吸收CO2能力比果实(块根)生长在地下的作物大;除花生在生育期间生物量吸收CO2量少于同期土壤排放以外,其余7种作物在生育期间生物量吸收CO2的量大于同期土壤排放,大多数农作物在生育期间具有碳汇功能,在撂荒期才体现碳源作用.     

植物硒吸收转化机制及生理作用研究进展

硒是大多微生物、动物及人类的必要微量元素,但其在植物生长发育中的生理作用至今存在争议.较低浓度硒具有促进植物生长、提高植物耐受能力的功能,而大部分植物在高浓度下表现出中毒现象.随着人类对摄入硒及环境硒污染问题的认识加深,作物硒生物强化与硒污染植物修复问题引起重视,推动了对硒在植物中的吸收积累及代谢调控的研究.近年来对植物硒吸收及转化的研究表明,不同硒水平下植物对硒吸收积累及生理响应存在差异,土壤环境因素对植物硒吸收及转化具有重要影响,对高聚硒植物硒代谢研究逐渐揭示出硒在植物体内的转化过程和调控机理等.本文总结了目前硒生物强化与植物修复方面的研究进展,对环境中硒分布特点、植物硒吸收及其影响因素、植物体内硒转化及其过程调控关键酶,以及硒在植物中的生理作用等进行了综述,并对植物硒生理及分子机制未来研究方向进行展望.     

作物的物质生产

植物的生活过程中,以遗传潜力为基础,不断地进行着物质、能量、形态结构和信息的转化。这种转化过程随时都受自然条件的影响,对作物来说,还要受到栽培条件的影响。这两种影响因素称为环境条件。在植物生长发育过程中,扣除植物的呼吸作用,脱落、分泌等消耗外,还进行着有机物、化学能和负熵的净积累,最终表现为比种子放大了许多倍的作物物质、能量和负熵的积累量。其中直接被人利用的部分为经济产量。一般所说的作物产量即指经济产量。     

驯化对作物微生物组多样性和群落结构的影响及作用途径

植物与共存微生物的相互作用对植物的生长、发育、健康等具有重大影响。人类驯化导致现代作物品种与其野生祖先在生理遗传特性、生长环境等方面存在明显差异, 这必然会影响作物与其微生物组的相互作用。理解驯化对作物微生物组的影响及其作用机理, 是充分应用微生物组进行作物改良或人工育种的重要理论基础。结合课题组前期研究基础, 该文综述了驯化对作物地下和地上部分细菌和真菌(尤其是益生菌和病原菌)群落组成和多样性影响的研究现状; 并结合驯化对作物植株形态、根系构型、根系分泌物等生理特征以及生长环境的影响, 分析了驯化塑造作物微生物组的作用途径, 提出了该领域值得重点关注的研究和发展方向。     

Nanotechnology a novel approach to enhance crop productivity

Nanobiotechnology provides novel set of tools to manipulate and enhance crop production using nanoparticles, nanofibres, nanoemulsions, and nanocapsules. Nanomaterials provide a platform to deliver agrochemicals and various macromolecules needed for plant growth enhancement and resistance to stresses. Smart delivery of agrochemicals increases the yield by optimizing water and nutrient conditions. Another added advantage is controlled release and site-directed delivery of agrochemicals. Further enhancement in quality and quantity in agriculture can be achieved by nanoparticle-mediated gene transformation and delivery of macromolecules that induces gene expression in plants. Various types of nanomaterials have been tested so far and the results have been promising in terms of productivity and quality enhancement.     

Genetic transformation technology: Status and problems

Summary Transfer of genes from heterologous species provides the means of selectively introducing new traits into crop plants and expanding the gene pool beyond what has been available to traditional breeding systems. With the recent advances in genetic engineering of plants, it is now feasible to introduce into crop plants, genes that have previously been inaccessible to the conventional plant breeder, or which did not exist in the crop of interest. This holds a tremendous potential for the genetic enhancement of important food crops. However, the availability of efficient transformation methods to introduce foreign DNA can be a substantial barrier to the application of recombinant DNA methods in some crop plants. Despite significant advances over the past decades, development of efficient transformation methods can take many years of painstaking research. The major components for the development of transgenic plants include the development of reliable tissue culture regeneration systems, preparation of gene constructs and efficient transformation techniques for the introduction of genes into the crop plants, recovery and multiplication of transgenic plants, molecular and genetic characterization of transgenic plants for stable and efficient gene expression, transfer of genes to elite cultivars by conventional breeding methods if required, and the evaluation of transgenic plants for their effectiveness in alleviating the biotic and abiotic stresses without being an environmental biohazard. Amongst these, protocols for the introduction of genes, including the efficient regeneration of shoots in tissue cultures, and transformation methods can be major bottlenecks to the application of genetic transformation technology. Some of the key constraints in transformation procedures and possible solutions for safe development and deployment of transgenic plants for crop improvement are discussed.     

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.     

Advances in Transgenic Rice Biotechnology

Rice is the most amenable crop plant for genetic manipulation amongst monocots due to its small genome size, enriched genetic map, availability of entire genome sequence, and relative ease of transformation. Improvement in agronomic traits of rice is bound to affect a sizeable population since it is a primary source of sustenance. Recent advances like use of ‘clean gene’ technology or matrix attachment regions would help improve rice transformation. Function of several novel genes and their promoters has been analyzed in transgenic rice. Significant progress has been made in introducing traits like herbicide, biotic stress and abiotic stress tolerance. Attempts also have been made to enhance nutritional characteristics of the grain and yield. Identification of genes controlling growth and development can be used to modify plant architecture and heading period. Transgenic rice can serve as a biofactory for the production of molecules of pharmaceutical and industrial utility. The drive to apply transgenic rice for public good as well as commercial gains has fueled research to an all time high. Successful field trials and biosafety of transgenic rice have been reported. This would act as a catalyst for greater acceptance of genetically modified food crops. The lessons learnt from rice can be extended to other cereals thereby opening new opportunities and possibilities.     

Regulation in Plant Stress Tolerance by a Potential Plant Growth Regulator, 5-Aminolevulinic Acid

Exogenous application of different plant growth regulators is a well-recognized strategy to alleviate stress-induced adverse effects on different crop plants by regulating a variety of physiobiochemical processes such as photosynthesis, chlorophyll biosynthesis, nutrient uptake, antioxidant metabolism, and protein synthesis, which are directly or indirectly involved in the mechanism of stress tolerance. Of various environmental factors, salinity, drought, and extreme temperature (low or high) considerably diminish plant growth and yield by modulating endogenous levels as well as signaling pathways of plant hormones. Of various plant hormones/regulators, a potential plant growth regulator, 5-aminolevulinic acid (ALA), is known to be effective in counteracting the injurious effects of various abiotic stresses in plants. Until now the mechanisms behind ALA regulation of growth under stress have not been fully elucidated. It is also not yet clear how far growth and yield in different crops can be promoted by exogenous application of ALA and whether this ALA-induced growth and yield promotion is cost-effective. Thus, in this review we discuss at length the effects of ALA in regulating growth and development in plants under a variety of abiotic stress conditions, including salinity, drought, and temperature stress. Furthermore, advances in the functional and regulatory interactions of this plant growth regulator with plant stress tolerance, as well as the effective mode of exogenous application of ALA in inducing stress tolerance in plants are also comprehensively discussed in this review. In the future, overaccumulation of ALA in plants through manipulation of gene(s) could enhance plant stress tolerance. Thus, genetic manipulation of plants with the goal of attaining increased synthesis/accumulation of ALA and hence improved stress tolerance under stress conditions is an important area for research.     

Direct DNA transfer using electric discharge particle acceleration (ACCELL™ technology)

Direct DNA transfer methods based on particle bombardment have revolutionized plant genetic engineering. Major agronomic crops previously considered recalcitrant to gene transfer have been engineered using variations of this technology. In many cases variety-independent and efficient transformation methods have been developed enabling application of molecular biology techniques to crop improvement. The focus of this article is the development and performance of electric discharge particle bombardment (ACCELL™) technology. Unique advantages of this methodology compared to alternative propulsion technologies are discussed in terms of the range of species and genotypes that have been engineered, and the high transformation frequencies for major agronomic crops that enabled the technology to move from the R&D phase to commercialization. Creation of transgenic soybeans, cotton, and rice will be used as examples to illustrate the development of variety-independent and efficient gene transfer methods for most of the major agronomic crops. To our knowledge, no other gene transfer method based on particle bombardment has resulted in variety-independent and practical generation of large numbers of independently-derived crop plants. ACCELL™ technology is currently being utilized for the routine transfer of valuable genes into elite germplasm of soybean, cotton, bean, rice, corn, peanut and woody species.     

Advances in development of transgenic pulse crops

It is three decades since the first transgenic pulse crop has been developed. Todate, genetic transformation has been reported in all the major pulse crops like Vigna species, Cicer arietinum, Cajanus cajan, Phaseolus spp, Lupinus spp, Vicia spp and Pisum sativum, but transgenic pulse crops have not yet been commercially released. Despite the crucial role played by pulse crops in tropical agriculture, transgenic pulse crops have not moved out from laboratories to large farm lands compared to their counterparts - 'cereals' and the closely related leguminous oil crop - 'soybean'. The reason for lack of commercialization of transgenic pulse crops can be attributed to the difficulty in developing transgenics with reproducibility, which in turn is due to lack of competent totipotent cells for transformation, long periods required for developing transgenics and lack of coordinated research efforts by the scientific community and long term funding. With optimization of various factors which influence genetic transformation of pulse crops, it will be possible to develop transgenic plants in this important group of crop species with more precision and reproducibility. A translation of knowledge from information available in genomics and functional genomics in model legumes like Medicago truncatula and Lotus japonicus relating to factors which contribute to enhancing crop yield and ameliorate the negative consequences of biotic and abiotic stress factors may provide novel insights for genetic manipulation to improve the productivity of pulse crops.