Applying horizontal gene transfer phenomena to enhance non-viral gene therapy

Horizontal gene transfer (HGT) is widespread amongst prokaryotes, but eukaryotes tend to be far less promiscuous with their genetic information. However, several examples of HGT from pathogens into eukaryotic cells have been discovered and mimicked to improve non-viral gene delivery techniques. For example, several viral proteins and DNA sequences have been used to significantly increase cytoplasmic and nuclear gene delivery. Plant genetic engineering is routinely performed with the pathogenic bacterium Agrobacterium tumefaciens and similar pathogens (e.g. Bartonella henselae) may also be able to transform human cells. Intracellular parasites like Trypanosoma cruzi may also provide new insights into overcoming cellular barriers to gene delivery. Finally, intercellular nucleic acid transfer between host cells will also be briefly discussed. This article will review the unique characteristics of several different viruses and microbes and discuss how their traits have been successfully applied to improve non-viral gene delivery techniques. Consequently, pathogenic traits that originally caused diseases may eventually be used to treat many genetic diseases.     

Susceptibility of local Agrobacterium tumefaciens strains to streptomycetes isolates from Jordan soils

Five strains of Agrobacterium tumefaciens were isolated and characterized from 12 different plant tumors. The susceptibility of these phytopathogens to antibiotics and to soil Streptomyces isolates was tested. Among the 90 Streptomyces isolates, only 12 were able to inhibit the growth of at least one A. tumefaciens strain. Four strains of A. tumefaciens were susceptible to streptomycin and cefotaxime. In addition, Streptomyces 404 strain was able to inhibit the growth of four strains of the Agrobacterium pathogens with an inhibition zone diameter ranged between 10 and 16 mm. The strong inhibitory effects of Streptomyces 404 strain on A. tumefaciens suggest the use of this strain as a promising agent to control crown gall disease.     

农杆菌介导的抗菌肽基因转化阳春砂愈伤组织的研究

目的确定遗传转化条件,将抗菌肽CN基因转入阳春砂愈伤组织。方法以阳春砂愈伤组织为受体材料,以农杆菌EHA105/pCAMBIA1305.2-CN工程细胞介导抗菌肽CN基因转化阳春砂,设计正交实验,通过分析gus报告基因的瞬时表达比较转化影响因素,并对目的基因CN进行PCR检测。结果农杆菌浓度、侵染时间、共培养温度、共培养时间及乙酰丁香酮浓度对转化率的影响有显著差异性。阳春砂愈伤组织遗传转化的最佳条件组合是:农杆菌浓度为OD600=0.5,侵染时间10 min,共培养温度24℃,共培养时间4 d,共培养培养基添加乙酰丁香酮200μmol.L-1。gus基因瞬时表达呈阳性的愈伤组织DNA经目的基因CN的PCR检测可见清晰的目的条带。结论建立了农杆菌介导的阳春砂愈伤组织的转化条件,目的基因CN已转入阳春砂愈伤组织。     

抗菌肽cecropin B和兔NP-1融合基因转化鱼腥草的研究

目的:将抗菌肽cecropin B和兔NP-1(CN)融合基因转入鱼腥草,培育鱼腥草基因工程新品种。方法:设计并合成抗菌肽融合基因CN,构建重组质粒pBI121-CN,并转入农杆菌LBA4404,以农杆菌介导法转化鱼腥草外植体,将卡那霉素筛选获得的再生抗性植株以快速筛选PCR法进一步筛选阳性植株,再提取基因组DNA进行PCR-Southern鉴定,RT-PCR分析目的基因在鱼腥草中的表达,以大肠杆菌K12抑菌圈实验和立枯丝核菌感染实验分析转基因鱼腥草抗菌能力。结果:抗菌肽基因已整合到转基因鱼腥草基因组中并表达,表现出抗菌能力增强的性状。结论:以抗菌肽融合基因CN转化鱼腥草,初步获得抗菌活性提高的转基因植株。     

圆叶牵牛毛状根的诱导及培养

目的：利用发根农杆菌,R1601,1000,1025,15834诱导约用植物圆叶牵牛产生毛状根。方法：采用共培养方法,通过对外植体、菌种、浸染时间、预培养、共培养、外源激素等因素对转化率的影响。结果：利川发根农杆菌1601,预培养60h的叶片、叶柄为转化材料,感染6～8min,加入1mg·L^-1 NAA转化率最高。结论：圆叶牵牛毛状根的诱导成功,为其遗传转化提供了依据。     

水飞蓟发状根培养体系的建立及其水飞蓟宾含量的测定

实验采用6种发根农杆菌R1601,R15834,R1000,A4,R1025,R1感染水飞蓟植体,诱导水飞蓟发状根及其水飞蓟宾的产生。6种发根农杆菌均能诱导水飞蓟产生发状根,A4表现出较强的对水飞蓟的感染能力。实验通过侵染时间、预培养、共培养、pH等因素确定了诱导水飞蓟发状根产生的条件,确定MS液体培养基适合水飞蓟发状根的增殖。经过PCR分子鉴定,发根农杆菌中的DNA质粒成功的整合到转化根的基因组中。使用液相色谱测定了水飞蓟发状根中水飞蓟宾含量是水飞蓟植物中的2.5倍。实验所建立的水飞蓟发状根培养系统,为研究水飞蓟发状根大量培养生产水飞蓟宾奠定了基础。     

Agrobacterium-mediated DNA transfer

Summary Agrobacterium tumefaciens naturally transfers DNA into plant cells and is clearly one of the most effective methods of directed DNA transfer presently available. Two kinds of vectors are commonly used. Cointegrative vectors have the foreign genes incorporated directly into the Ti plasmid. Binary vectors carry two plasmids; the main Ti plasmid where most of the T-DNA has been removed, and a second plasmid containing the foreign genes between the usual border sequences. The vir genes on the main plasmid function to mobilize the foreign genes into a plant cell. Most plant transformation methods follow the procedure of cocultivating wounded tissue with vir-gene-induced bacteria. The cocultivation step is followed by transfer to a selective medium containing antibiotics to kill the bacterium and to allow only growth of transformed tissue. Several selectable markers are available that include resistance to antibiotics, herbicides, or drugs. In addition, several scorable markers such as the bacterial glucuronidase, chloramphenicol acetyl transferase, and the Agrobacterium opine genes are used to verify transformation. Southern blotting and inheritance of transferred genes are ultimately used to demonstrate stable transformation.     

白藜芦醇合酶基因的克隆及丹参的转化

目的为探索利用分子生物学技术培育新型药用植物的新途径,将外源的白藜芦醇合酶(RS)基因导入到丹参中表达,以改善或增加丹参的效用。方法根据已公布的核苷酸序列,利用引物悬挂延伸法,经过3次扩增,最终从葡萄基因组DNA中获得完整的RScDNA基因序列;以质粒pBin438为基础,构建含有RS目的基因的组成型植物表达载体。在根癌农杆菌介导下,利用叶盘法转化丹参,进而通过PCR、PCR-Southern杂交对不同的转基因植株进行筛选与检测。结果总共得到了45棵卡那霉素抗性植株,经PCR和PCR-Southern杂交检测,确定葡萄RS基因已整合到部分转基因丹参苗的基因组中。结论成功建立了白藜芦醇合酶基因转化丹参的体系,并获得了转基因植株。     

药用植物商陆毛状根培养系统的建立

目的:建立药用植物商陆(Phytolacca acinosa Roxb.)的毛状根离体培养系统.方法:分别用发根农杆菌A4、R1600、C58C1 3个菌株感染商陆的子叶外植体,获得毛状根,并筛选了优质株系;考察了影响毛状根生长的因素;测定了毛状根的生长曲线;利用PCR和高压纸电泳法对毛状根进行tDNA转化的检测.结果:利用发根农杆菌A4、R1600、C58C1 3种菌株成功地从商陆中诱导出毛状根;以水解酪蛋白为氮源、以麦芽糖为碳源最有利于商陆毛状根的生长;毛状根的生长曲线呈"S"形,24 d时质量达到最大(增长18倍);PCR及高压纸电泳检测结果表明Ri质粒的tDNA已整合进毛状根中.结论:成功建立了商陆毛状根离体培养系统,为进一步进行药用成分的工业化生产和引入外源基因改良性状奠定了基础.