CMV抑制PVYN CP基因沉默及其介导的抗病性

以前曾报道用RNA介导的抗病毒策略,获得了高度抗病的表达马铃薯Y病毒坏死株系外壳蛋白基因(PVY^N CP)的转基因烟草,并对T1、T2代转基因植株进行了遗传和抗病性分析。此次以T,代转基因植株为试验材料,在筛选高度抗病植株并证明其抗病性是基于转基因沉默的基础上,采用Northern杂交的方法,证明CMV侵染抑制了转基因植株中PVY^N CP基因的沉默,而且CMV对PVY^N CP基因沉默的抑制部位是发生在接种后的新生叶上,接种叶及其下部叶片中PVY^N CP基因沉默则未受到影响。采用ELISA方法对CMV PVY^N复合接种的转基因植株进行PVY^N检测,结果表明,接种叶及下部叶没有检测到PVY^N,植株叶片对PVY^N表现为抗病。而在CMV接种后植株新生叶中则检测出了高滴度的PVY^N,植株叶片对PVY^N表现为感病。该文报道了在表达PVY^N CP基因的RNA介导抗性转基因植株中,异源病毒侵染抑制了转基因的沉默,并导致转基因植株的抗病性丧失。     

黄瓜花叶病毒互补型载体可与CP转基因发生重组

为了探讨利用黄瓜花叶病毒(CMV)作为表达载体的可行性,克隆了山东株(SD)CMV RNA3的全长cDNA,并测定了全序列.采用定点突变的方法在衣壳蛋白(CP)基因起始密码子处改造出一个NsiⅠ位点.以绿色荧光蛋白(GFP)基因置换SD-CMV RNA3 cDNA的CP基因.将Fny株CMV RNA1,RNA2和嵌合SD-CMV RNA3的cDNA分别克隆在35 S启动子和终止子之间构建成表达载体.在烟草原生质体中验证了该表达载体可以表达GFP.然后将其接种到表达SD CP的转基因烟草上,试图构建成一个互补型载体.接种10d后,18棵植株中,有5棵的接种叶和其中1棵的系统叶上可检测到表达的GFP.然而1个月后,所有接种植株中都检测不到GFP.通过RT-PCR及序列分析,证实在互补系统中CMV载体与CP转基因发生了重组.上述结果对这种CMV互补型载体的可行性提出了质疑,同时也揭示了转CMV CP基因抗病毒植物的生物安全性中存在的新的问题.     

黄瓜花叶病毒和烟草花叶病毒在双抗转基因线辣椒内的增殖

本试验以转化CMV CP和TMV CP基因的转基因线辣椒纯合系植株作为研究试材 ,比较了单独或混合接种CMV和TMV后 ,转化线辣椒的抗病性表达特点 ,并测定了两种病毒在植株体内的病毒含量。结果表明 :转化线辣椒不仅能抵抗CMV和TMV的单独侵染 ,而且还能抵抗CMV和TMV的复合侵染。转化线辣椒表现为系统症状延迟出现 7 15d ,显症株率和病害严重度级别大幅度降低 ,CMV和TMV在接种叶、新生叶中的病毒含量明显减低。转基因线辣椒原生质体作为研究试材接种CMV ,测定病毒含量结果表明 :CMV病毒的增殖在转基因线辣椒原生质体内受到明显抑制。在CMV接种浓度为 4 0 μg/mL ,感染原生质体 4 8h后 ,CP(- )植株原生质体内CMV是CP( )的 4 .2倍。这一结果揭示了转基因线辣椒具有抑制病毒增殖的抗病性。     

黄瓜花叶病毒和烟草花叶病毒在双抗转基因线辣椒内的增殖

本试验以转化CMV-CP和TMV-CP基因的转基因线辣椒纯合系植株作为研究试材,比较了单独 或混合接种CMV和TMV后,转化线辣椒的抗病性表达特点,并测定了两种病毒在植株体内的病 毒含量.结果表明转化线辣椒不仅能抵抗CMV和TMV的单独侵染,而且还能抵抗CMV和TMV的 复合侵染.转化线辣椒表现为系统症状延迟出现7-15d,显症株率和病害严重度级别大幅度降低, CMV和TMV在接种叶、新生叶中的病毒含量明显减低.转基因线辣椒原生质体作为研究试材接 种CMV,测定病毒含量结果表明CMV病毒的增殖在转基因线辣椒原生质体内受到明显抑制. 在CMV接种浓度为40μg/mL,感染原生质体48h后,CP(-)植株原生质体内CMV是CP(+)的4.2倍 .这一结果揭示了转基因线辣椒具有抑制病毒增殖的抗病性.     

黄瓜花叶病毒卫星RNA致弱辅助病毒的机理

分析了卫星RNA致弱的黄瓜花叶病毒 (CMV)侵染的烟草叶绿体内的CP浓度与花叶症状的严重程度成正相关 .用番茄不孕病毒 (TAV)接种表达CMV卫星RNA的转基因烟草叶绿体中 ,TAV- CP含量明显比不含卫星RNA的TAV株系侵染的低 ,而在细胞质中TAV -CP含量无差别 .用完整游离叶绿体进行体外跨膜运输试验 ,CMV- CP能快速进入离体叶绿体 ,CP降低叶绿体动力学荧光光谱 .将CMV的CP基因与 1 ,5 二磷酸核酮糖羧化酶小亚基引导肽基因进行体外拼接 .借助农杆菌转化烟草 .转基因烟草表现出黄化、根系发育受抑制 ,产生类似病毒侵染的症状 .     

侵染辣椒的黄瓜花叶病毒CP基因的序列分析、原核表达及抗血清制备

从吉林长春感病辣椒上获得一黄瓜花叶病毒(Cucumber mosaic virus,CMV)分离物(CMV-CC),根据GenBank中已登录的CMV外壳蛋白(coat protein,CP)基因核苷酸序列设计简并引物,通过RT-PCR的方法克隆到了长度为657 bp的目的片段。序列分析表明,CMV-CC与CMVI组各分离物核苷酸同源性为93.2%-97.9%。根据完整CP基因核苷酸序列构建的系统进化树显示:38个CMV分离物可分为3个组,CMV-CC属于CMV的IB亚组。将CMV-CC CP基因与原核表达载体pET-22b(+)连接,在大肠杆菌BL21(DE3)诱导表达出分子量约27 kD的融合蛋白。表达的融合蛋白经树脂纯化后免疫家兔制备了抗血清。用间接ELISA测定抗血清效价为1/4 096。Western blotting分析表明制备的抗血清对CP有高度特异性,为准确、快速地检测CMV奠定了基础。     

转不可翻译PVYN CP基因烟草的抗病性分析

我们曾报道表达不可翻译PVY~N CP基因的转基因烟草抗病性是由RNA介导的,其抗病性类似于转录后的基因沉默(PTGS)。本研究以这类不同抗性的Tn代转基因烟草植株为材料,对自交后的T1代转基因植株的遗传和抗病性进行了分析,并选取部分T_1代抗病株系自交留种。对T_2代RNA介导抗病性转基因植株进行了分子分析和一系列抗病性研究。结果表明,含1-2个转基因拷贝的T_0代感病植株,在T_1代中的Km抗性分离符合单位点插入的3∶1的遗传规律;含3个或3个以上转基因拷贝的T_0代中抗或高抗植株,在T_1代中的Km抗性分离符合多位点插入的15∶1或63∶1的遗传规律。大多数T_1、T_2代转基因植株的抗病性与转基因拷贝数成正相关,转基因在T_1、T_2代植株中能够转录表达,且转基因植株之间转基因mRNA在细胞质中的积累水平与转基因植株的抗病性成负相关。转基因植株的抗病性能够在T_1、T_2代中遗传,且T_2代转基因植株的抗病性具有以下特征:1)既抗病毒粒体又抗病毒RNA的侵染,且这种抗病性不受接种物剂量的影响;2)抗病谱较窄,只对PVY的某些株系具有高度抗病性;3)与传毒方式无关,既抗摩擦接种又抗带毒蚜虫接种;4)与植株的发育阶段没有关系。     

黄瓜花叶病毒基因组不同部分及卫星RNA介导的对植株的保护及其作用机理

根据病原物介导的对自身抗性的理论,大量开展了将CMV基因组的单个或多个片断转入植物体内的研究,从而使该植株能够抵抗或延迟受CMV的侵染,CP,RP,MP基因是CMV基因组的重要组成部分,用来转化植株取得了不同程度的抗性效果,另外有些CMV株中存在着起致弱作用的卫星RNA,直接对植株接种含卫星RNA的CMV弱毒或用卫星RNA的cDNA转化植株都会减轻CMV强毒对该植株的侵害,CMV基因组不同组分进入植物体内后,它们对植株产生保护作用的机理不同,文中分别加以阐述。     

MDMV CP基因的克隆及其转基因玉米的研究

用RT-PCR方法分离了玉米矮花叶病毒外壳蛋白基因(MDMV CP),并且利用基因枪法将该基因导入玉米优良自交系18-599红、18-599白幼胚诱导的愈伤组织中。转化的愈伤组织在Bialaphos浓度(PPT)为8mg／L、10mg/L、5mg／L的筛选压下经过3次抗性筛选后,分别再生出可育植株12株和6株。PCR和Southem检测结果说明CP基因已整合到玉米自交系基因组中。对T1代转基因植株进行病毒人工接种试验,结果表明对照植株全部表现为感染玉米矮花叶病的典型症状,而转基因植株后代呈现不同程度的抗性。     

表达黄瓜花叶病毒卫星RNA的转基因烟草耐烟草花叶病毒

表达黄瓜花叶病毒(CMV)的卫星RNA的转基因烟草可以抗CMV的侵染.为了决定这些植物对其它病毒,如烟草花叶病毒(CMV)的安全性,我们对这些植物接种CMV.结果发现 卫星RNA可减弱TMV引起的症状,井降低病情指数,然而却对TMV在植物中的积累没有明显影响.这一发现有助于对卫星RNA抗病机制的理解,有助于含卫星RNA的生防制剂及表达病毒卫星RNA的转基因植物的应用.本文在国际上首次报道卫星RNA可减弱非相关病毒引起的症状.1 材料和方法1.1 病毒及植物烟草花叶病毒(TMV),烟草G140种子及枯班三生烟种子均为中国科学院微生物研究所病毒室保存;含黄瓜花叶病毒卫星RNA-R1基因的烟草G140(烟Sat-G140)为中国科学院微生物研究所病毒室培育,所用材料为第三代种子.     

Extreme resistance to cucumber mosaic virus (CMV) in transgenic tomato expressing one or two viral coat proteins

For the production of broad commercial resistance to cucumber mosaic virus (CMV) infection, tomato plants were transformed with a combination of two coat protein (CP) genes, representing both subgroups of CMV. The CP genes were cloned from the CMV-D strain and Italian CMV isolates (CMV-22 of subgroup I and CMV-PG of subgroup II) which have been shown to produce severe disease symptoms. Four plant transformation vectors were constructed: pMON18774 and pMON18775 (CMV-D CP), pMON18831 (CMV-PG CP) and pMON18833 (CMV-22 CP and CMV-PG CP). Transformed R0 plants were produced and lines were selected based on the combination of three traits: CMV CP expression at the R0 stage, resistance to CMV (subgroup I and/or II) infection in growth chamber tests in R1 expressing plants, and single transgene copy, based on R1 segregation. The results indicate that all four vector constructs generated plants with extremely high resistant to CMV infection. The single and double gene vector construct produced plants with broad resistance against strains of CMV from both subgroups I and II at high frequency. The engineered resistance is of practical value and will be applied for major Italian tomato varieties. This revised version was published online in June 2006 with corrections to the Cover Date.     

Cucumber mosaic virus coat protein-mediated protection

Transgenic tobacco plants (CP +) that express the coat protein gene of cucumber mosaic virus (CMV)-Y strain were highly protected from infection with either CMV virions or CMV RNA, while transgenic protoplasts were also protected from infection with CMV virions but not with CMV RNA. CP + plants showed greater susceptibility to infection with satellite RNA-free CMV-Y than CMV-Y containing satellite RNA. At temperatures above 30°C, CP + plants did not or poorly resist infection with CMV. Elevated temperature affected the accumulation of CP rather than its mRNA, suggesting that CP molecules are mainly involved in virus resistance in CP + plants.     

Virus Movement Protein Gene Mediated Resistance Against Cucumber Mosaic Virus Infection

Tobacco (Nicotiana tabactum L. ) "NC89" plants were transformed with deletion mutant of cucumber mosaic virus (CMV) movement protein (MP) gene and full-length CMV MP gene, respectively. The transformed plants were analyzed with polymerase chain reaction (PCR), PCR-Southem, Southern and Western blots. R0 generation of the transgenic plants were inoculated with CMV. Five out of 10 lines of tobacco plants (BMPK) transformed with CMV MP deletion mutant gene showed high resistance to CMV infection and remained symptomless for up to 50 days post-inoculation. In contrast, tobacco plants (BMPR) transformed with full-length CMV MP gene did not show resistance to CMV infection. However, most of the infected full-length CMV MP gene transgenic plants recovered by showing none or very mild mosaic symptoms in 40 days post-inoculation. The results of R1 generation of the BMPK transgenic plants tested under field conditions showed that all 5 lines of transgenic plants could delay the virus disease development.     

Expression of the gene encoding the coat protein of cucumber mosaic virus (CMV) strain WL appears to provide protection to tobacco plants against infection by several different CMV strains.

The gene (cp) encoding the coat protein (CP) of cucumber mosaic virus (CMV) strain WL (CMV-WL, which belongs to CMV subgroup II) was custom polymerase chain reaction (CPCR)-engineered for expression as described by Slightom [Gene 100 (1991) 251-255]. CPCR amplification was used to add 5'- and 3'-flanking NcoI sites to the CMV-WL cp gene, and cp was cloned into the expression vector, pUC18cpexp. This CMV-WL cp expression cassette was transferred into the genome of tobacco (Nicotiana tabacum cv. Havana 423) via the Agrobacterium T-DNA transfer mechanism. R0 plants that express the CMV-WL cp gene were subcloned, propagated, and challenge-inoculated with CMV-WL. Several R0 plant lines showed excellent protection against CMV-WL infection; however, plants found to accumulate the highest CP levels did not show the highest degree of protection. Thus in our case, CP levels appear not to be a useful predictor of the degree of protection. Plants from the best protected CMV-WL cp gene-expressing R0 tobacco lines were also inoculated with CMV strains belonging to the other major CMV subgroup (subgroup I), CMV-C and CMV-Chi, and compared in a parallel experiment with a transgenic tobacco plant line that expresses the CMV-C cp gene. Plants expressing the CMV-WL cp gene appeared to show a broader spectrum of protection against infection by the various CMV strains than plants expressing the CMV-C cp gene.     

Transgenic tobacco plants expressing the coat protein of cucumber mosaic virus show different virus resistance

Transgenic tobacco (Nicotiana tabacum cv. Xanthi-nc) plants were regenerated after cocultivation of leaf explants withAgrobacterium tumefaciens strain LBA4404 harboring a plasmid that contained the coat protein (CP) gene of cucumber mosaic virus (CMV-As). PCR and Southern blot analyses revealed that the CMV CP gene was successfully introduced into the genomic DNA of the transgenic tobacco plants. Transgenic plants (CP⁺) expressing CP were obtained and used for screening the virus resistance. They could be categorized into three types after inoculation with the virus: virus-resistant, delay of symptom development, and susceptible type. Most of the CP⁺ transgenic tobacco plants failed to develop symptoms or showed systemic symptom development delayed for 5 to 42 days as compared to those of nontransgenic control plants after challenged with the same virus. However, some CP⁺ transgenic plants were highly susceptible after inoculation with the virus. Our results suggest that the CP-mediated viral resistance is readily applicable to CMV disease in other crops.     

Rapid production and field testing of homozygous transgenic tobacco lines with virus resistance conferred by expression of satellite RNA and coat protein of cucumber mosaic virus

A procedure for the fast production of homozygotic transgenic plants was developed. Leaf discs of haploid tobacco plants from anther cultures were transformed with a chimaeric vector containing coat protein (CP) and satellite RNA (Sat-RNA) genes from cucumber mosaic virus (CMV). One-hundred-and-twelve Kanamycin-resistant transformed haploid plants were subjected to selection based on the expression of both CP and Sat-RNA. Eighty-nine transgenic plants expressing both genes were selected and tested for their resistance to CMV by inoculation with high concentration of CMV (200 g ml^–1). Only five plants showed no symptoms of viral infection 30 days after inoculation. These plants were then diploidized by colchicine treatment. Three homozygous diploid lines with high levels of resistance to CMV were obtained after only one generation. The three transgenic lines were further tested under field conditions. The results showed that the progenies of these transgenic lines were homozygous and were highly resistant to CMV under natural field infection and manual inoculation conditions.     

Recombination with coat protein transgene in a complementation system based on Cucumber mosaic virus (CMV)

In order to study the feasibility of Cucumber mosaic virus (CMV) as an expression vector, the full-length cDNA of RNA 3 from strain SD was cloned and the sequence around the start codon of the coat protein (CP) gene was modified to create an Nsi I site for insertion of foreign genes. The CP gene was replaced by the green fluorescent protein (GFP) gene. The cDNAs of Fny RNAs 1 and 2 and the chimeric SD RNA 3 were cloned between the modified 35S promoter and terminator. Tobacco protoplasts were transfected with a mixture of the viral cDNAs containing 35S promoter and terminator as a replacement vector and expressed GFP. A complementation system was established when the replacement vector was inoculated onto the transgenic tobacco plants expressing SD-CMV CP. GFP was detected in the inoculated leaves in 5 of 18 tested plants and in the first upper systemic leaf of one of the 5 plants ten days after inoculation. However, no GFP could be detected in all the plants one month after inoculation. Recombination be     

Transgenic Melon and Squash Expressing Coat Protein Genes of Aphid-borne Viruses do not Assist the Spread of an Aphid Non- transmissible Strain of Cucumber Mosaic Virus in the Field

Transgenic melon and squash containing the coat protein (CP) gene of the aphid transmissible strain WL of cucumber mosaic cucumovirus (CMV) were grown under field conditions to determine if they would assist the spread of the aphid non-transmissible strain C of CMV, possibly through heterologous encapsidation and recombination. Transgenic melon were susceptible to CMV strain C whereas transgenic squash were resistant although the latter occasionally developed chlorotic blotches on lower leaves. Transgenic squash line ZW-20, one of the parents of commercialized cultivar Freedom II, which expresses the CP genes of the aphid transmissible strains FL of zucchini yellow mosaic (ZYMV) and watermelon mosaic virus 2 (WMV 2) potyviruses was also tested. Line ZW-20 is resistant to ZYMV and WMV 2 but is susceptible to CMV. Field experiments conducted over two consecutive years showed that aphid-vectored spread of CMV strain C did not occur from any of the CMV strain C-challenge inoculated transgenic plants to any of the uninoculated CMV-susceptible non- transgenic plants. Although CMV was detected in 3% (22/764) of the uninoculated plants, several assays including ELISA, RT- PCR-RFLP, identification of CP amino acid at position 168, and aphid transmission tests demonstrated that these CMV isolates were distinct from strain C. Instead, they were non-targeted CMV isolates that came from outside the field plots. This is the first report on field experiments designed to determine the potential of transgenic plants expressing CP genes for triggering changes in virus-vector specificity. Our results indicate that transgenic plants expressing CP genes of aphid transmissible strains of CMV, ZYMV, and WMV 2 are unlikely to mediate the spread of aphid non-transmissible strains of CMV. This finding is of practical relevance because transgenic crops expressing the three CP genes are targeted for commercial release, and because CMV is economically important, has a wide host range, and is widespread worldwide.     

Transgenic tobacco plants expressing a coat protein gene of tobacco mosaic virus are resistant to some other tobamoviruses

Transgenic tobacco plants expressing the coat protein (CP) gene of tobacco mosaic virus were tested for resistance against infection by five other tobamoviruses sharing 45-82% homology in CP amino acid sequence with the CP of tobacco mosaic virus. The transgenic plants (CP+) showed significant delays in systemic disease development after inoculation with tomato mosaic virus or tobacco mild green mosaic virus compared to the control (CP-) plants, but showed no resistance against infection by ribgrass mosaic virus. On a transgenic local lesion host, the CP+ plants showed greatly reduced numbers of necrotic lesions compared to the CP- plants after inoculation with tomato mosaic virus, pepper mild mottle virus, tobacco mild green mosaic virus, and Odontoglossum ringspot virus but not ribgrass mosaic virus. The implications of these results are discussed in relation to the possible mechanism(s) of CP-mediated protection.