TRANSGENIC PLANTS EXPRESSING BACILLUS THURINGIENSIS DELTA-ENDOTOXINS

Commercial varieties of transgenic Bacillus thuringiensis (Bt) plants have been developed in many countries to control target pests. Initially, the expression of native Bt genes in plants was low due to mRNA instability, improper splicing, and post-translation modifications. Subsequently, modifications of the native Bt genes greatly enhanced expression levels. This is a review of the developments that made modem high-expression transgenic Bt plants possible, with an emphasis on the reasons for the low-level expression of native Bt genes in plant systems, and the techniques that have been used to improve plant expression of Bt toxin genes.     

培育具有安全选择标记或无选择标记的转基因植物

转基因植物中选择标记的安全性已成为植物基因工程研究的热点之一。从两个方面可以解决转基因植物中的选择标记问题。一是选用安全的正向选择标记,主要是与糖代谢和激素代谢相关的基因。二是构建能去除选择标记基因的转化系统,主要有共转化系统、双T-DNA边界载体系统、位点特异性重组系统和转座子系统等。这些植物基因工程的方法将有助于培育安全的转基因植物。 Abstract:The bio-safety of selective markers in transgenic plants has been a hot spot in the field of plant genetic engineering.To solve the problem of selective markers in the transgenic plants,two means of producing transgenic plants have been developed.One is the utilization of bio-safe positive selective markers which are genes mainly related to metabolism of auxins and carbohydrates.The other is the establishment of transformation systems allowing marker genes to be eliminated from the transgenic plants,which include co-ransformation,double T-DNA border vectors,site-specific recombination and transposition.All these approaches of plant genetic engineering will benefit breeding transgenic plants with bio-safety.     

Effect of cDNA fragments in different length derived from Potato Virus Y coat protein gene on the induction of RNA-mediated virus resistance

Potato virus Y (PVY) is a main viral pathogen infecting economic crops such as potato and tobacco plants. Genetic engineering has been so far the most effective method to produce viral resistant plants. Be-cause of the shortage of viral resistant genes in plants, cDNAs derived from viral genes were often used for induction of resistance in transgenic plants (the so- called pathogen-derived resistance)[1]. Among the genes used in the pathogen-derived resistance strategy, the coat protein gen…     

植物基因工程表达载体的改进和优化策略

外源基因在转基因植物中表达效率低一直是令相关研究者困扰的一个问题.转基因植物的生物安全性最近在全球范围内开始引起世人的担忧.本文简要介绍了近年来在植物表达载体构建方面所采用的一些新策略,这些策略有助于增强外源基因的表达水平、提高生物工程体的安全性。 Abstract:The low expression level of foreign genes in transgenic plants is a puzzling question for researchers in plant genetic engineering.The biosafety concern is now causing a growing public wariness of transgenic plants around the world.This article reviews the new strategies currently used in construction of plant expression vector for plant genetic engineering.These strategies are important for obtaining better expression of foreign genes and developing safer transgenic plants.     

Creation of Transgenic Bananas Expressing Human Lysozyme Gene for Panama Wilt Resistance

Human lysozyme （HL） inhibits Fusarium oxysporum （FocR4） growth in vitro. To obtain transgenic bananas （Musa spp.） that are resistant to Panama wilt （F. oxysporum）, we introduced an HL gene that is driven by a constitutive cauliflower mosaic virus 35S promoter into the banana via Agrobacteriummediated transformation. PCR confirmed that 51 transgenic plants were obtained. The development of Panama wilt symptoms were examined after the plants had been grown in pots. The non-transgenic plants developed typical fusarium symptoms 60 d after FocR4 inoculation, whereas 24 of 51 transgenic plants remained healthy. The transgenic banana plants that showed resistance to FocR4 in the pots were then planted in a field that was heavily infected with FocR4 for further investigation. Eleven of 24 plants devel- oped symptoms before bud emergence; another 11 plants showed symptoms after bud emergence and the remaining two plants, H-67 and H-144, remained healthy and were able to fruit. Northern blotting analysis demonstrated that H-67 and H-144, bearing the strongest resistance to Panama wilt, had the highest level of HL expression and that the expression of HL was well correlated with the FocR4 resistance of transgenic plants. We conclude that Agrobacterium-mediated transformation, with the assistance of particle bombardment, is a powerful approach for banana transformation and that a transgenic HL gene can cause resistance of the crop to FocR4 in the field.     

双价抗虫基因叶绿体共转化植株抗虫性及其后代表型分析

利用基因枪法将含有水稻巯基蛋白酶抑制剂(Oryzacystatin,OC)基因烟草叶绿体表达载体和含有苏云金芽孢杆菌晶体毒蛋白基因(Bt cry IAc)烟草叶绿体表达载体,共转化烟草叶绿体,获得壮观霉素抗性植株。转基因植株抗棉铃虫试验表明,转双价抗虫基因植株比转单一抗虫基因植株具有更强的杀虫活性。转基因植株后代Southern检测及其遗传学分析试验证明,双价抗虫基因可以稳定地遗传给后代,且表现为叶绿体特有的母系遗传规律。 Abstract:The Bt gene and OC gene were cotransformed to tobacco chloroplast with particle bombardment method and spectinomycin resistance tobacco seedlings were obtained.Bioassays showed that the transgenic tobacco containing both genes had enhanced toxicity to the larvae of cotton bollworm (helicoverpa zea) by comparison with the plants containing only Bt or OC gene.Southern-blotting analysis and genetic analysis of progenies showed that the Bt and OC gene expressed and was inherited maternally to the progenies.     

Signal Peptide of Potato PinII Enhances the Expression of Cry1Ac in Transgenic Tobacco

Insect-resistant plants have been developed throughexpression of insecticidal proteins from Bacillusthuringiensis (Bt) in the early 1980s [1,2]. However, forcontrol of insect pests, it is necessary to increase theexpression of Bt protein overall or in specific plant tissues.To increase the expression level, synthetic Bt genes havebeen developed and used to produce transgenic plants[2–5]. A number of approaches have been taken to increasethe expression level of foreign proteins in transgeni…     

Detection and monitoring of insect resistance to transgenic Bt crops

Transgenic crops expressing Bacillus thuringiensis （Bt） endotoxins havebecome one of the most important tools for managing corn and cotton insect pests in the US and other countries. The widespread adoption of transgenic Bt crops could place a high degree of selection pressure on the target insect populations and accelerate development of resistance, raising concerns about the long-term durability of Bt plants as an effective pest management tool. Conservation of Bt susceptibility in insects has become one of the most active research areas in modern agriculture. One of the key factors for a successful Bt resistance management plan is to have a cost-effective monitoring system that can provide information on. （i） the initial Bt resistance allele frequencies at low levels in field insect populations; and （ii） early shifts in Bt resistance allele frequencies so that proactive measures for managing resistance can be deployed well before field control failures. Developing such a monitoring program has been difficult because： （i） resistance traits that occur at very low frequencies are hard to detect; （ii） many factors affect the sensitivity and accuracy of a Bt resistance monitoring program; and （iii） monitoring resistance is costly. Several novel methods for detecting Bt resistance alleles developed during the last decade have made a cost-effective monitoring system possible. Future studies should focus on how to improve and standardize the methodologies for insect sampling and Bt resistance detection.     

植物防御系统中抗病相关基因的研究进展

本文论述了植物防御系统中抗病相关基因（resistance gene,R基因）的研究进展。列表总结了迄今已克隆的R基因,并将其归为四种不同的类型。综述了不同基因表达产物-R蛋白在细胞中的定位及其相应的功能。此外,还对R基因编码区的多态性、R基因在染色体上排列方式以及R基因的进化与起源等问题进行了讨论。 Abstract:This review comments on recent advances in research of disease resistance genes(R Genes) in defence system of plants.The R genes cloned up to date are summarized and classified roughly into four classes listed in the Table 1.The location and the founction of the R proteins,i.e.,the expressed products of different R genes in the cells are reviewed.In addition,the polymophism of coding region of R genes,the different fashions of R gene arrangement on the chromosomes,and the evolution and origin of R genes are discussed.