植物病毒的反RNA干扰机制

RNA干扰(RNAi)是个古老而保守的机制,其作用如同“基因组的免疫系统”,广泛存在于真核生物真菌、植物、动物中,是天然的抵御病毒侵袭的系统.植物病毒在和植物长期而复杂的协同进化中,为了生存繁殖,提高自身复制、运动、感染寄主的能力,也演化出了对付宿主沉默反应的机制,即反干扰机制.目前的研究表明,病毒编码沉默抑制子是反干扰机制的最主要方式.本文主要就病毒编码的沉默抑制子作用特点和功能进行了概述.并介绍了缺损干扰RNA及卫星RNA的特殊复杂二级结构、快速复制与运动躲避沉默信号等反干扰机制,以及探讨了病毒反干扰的研究应用前景.     

植物病毒编码的RNA沉默抑制因子

RNA沉默广泛存在于真核生物中,是一种发生于RNA水平的基因表达调节机制。寄主植物利用RNA沉默防御病毒的入侵,而病毒编码抑制因子以抵御这种防卫反应,从而达到在植物体内扩增、形成侵染的目的。近几年越来越多的沉默抑制因子被鉴定出来。本文就已鉴定出的沉默抑制因子的特点进行了系统介绍。     

植物中RNA沉默机制的研究进展

近年来,人们对植物中RNA沉默机制的的认识日渐清晰,小RNAs在其中发挥重要作用.文章综述了植物中RNA沉默的机制、RNA沉默的主要途径及其在防御外源DNA序列入侵过程中的主要功能.并简要介绍了由DNA病毒编码的基因沉默抑制子在对抗宿主沉默反应的作用.文章最后阐述了对RNA沉默进行深入研究的必要性,对需要研究的问题进行了分析,为抗病毒作物育种提供了有力依据.     

病毒诱导的基因沉默及其在植物功能基因组学研究中的应用

病毒诱导的基因沉默(VIGS)是植物体中天然存在的一种抵御外源核酸入侵的防御系统,正常情况下保护植物免受病毒的侵染.植物的这种防御机制可被病毒RNA激活,属于转录后基因沉默现象.如果在病毒载体中插入目标基因片段,侵染寄主植物后,植物会表现出目标基因功能丧失或表达水平下降的表型.利用这种机制,可以确定基因功能.目前,这种技术有望发展成为一种简单、快速、高通量的分析已知序列基因功能的方法.文中综述了VIGS技术的原理与发展,并讨论该技术在植物功能基因组学研究中的应用前景.     

植物基因沉默的研究进展

植物抗病毒机制是目前研究的热点.在长期的进化过程中,植物形成了一系列复杂有效的防御机制来抵御、破坏病原物的侵染.近年来,基因沉默作为一个重要的细胞内防御外源核酸的机制,越来越受到科学家的重视.对这一领域的研究不仅能够了解基因沉默的机理,并且可以为利用该机制构建抗病毒转基因植物提供理论指导和技术支持.     

RNA干扰及其应用

RNA干扰现象是指外源双链RNA进入细胞后引起与其同源的mRNA特异性降解，从而导致该基因表达的沉默。它是真核生物在长期的进化中形成的一种保守的防御机制，它的出现为生物学家提供了一种快速、简便的反向遗传学技术。RNA干扰已成为一种进行基因功能分析的强有力的工具，并有望在对病毒的防御及基因治疗中发挥重要的作用。     

病毒诱导的基因沉默

病毒诱导基因沉默(Virus-induced gene silencing,VIGS)是近年发现的一种转录后基因沉默的现象,是快速鉴定植物基因功能的一种反向遗传学新技术,近年来成为植物基因功能研究的有力工具.文章从病毒诱导基因沉默的发现、作用机制、优势、病毒抑制子及其在植物基因功能研究和植物抗病毒的应用等方面进行了综述.     

病毒诱导的基因沉默

病毒诱导基因沉默(Virus-induced gene silencing,VIGS)是近年发现的一种转录后基因沉默的现象,是快速鉴定植物基因功能的一种反向遗传学新技术,近年来成为植物基因功能研究的有力工具.文章从病毒诱导基因沉默的发现、作用机制、优势、病毒抑制子及其在植物基因功能研究和植物抗病毒的应用等方面进行了综述...     

RNA干涉研究进展

RNA干涉(RNAi)是生物体内的一种通过双链RNA(dsRNA)来抵抗病毒入侵和抑制转座 子活动的自然机制.快速发展的RNAi技术为抑制特异性基因的表达提供了有利的工具.到目前为 止,在真菌、拟南芥、线虫、锥虫、水螅、涡虫、果蝇、斑马鱼、小鼠等真核生物中都发现存在基因沉默 机制.RNAi作为基因沉默的工具,为基因功能研究、基因治疗、药物研究与开发等许多领域开辟了 一条新路.     

RNA干涉与基因沉默研究进展

生物体内导入双链RNA(dsRNA)后会引起体内同源基因特异的沉默，这种现象称为RNA干涉(RNAi)．基因沉默是生物体基因表达调控的一种重要机制，具有重要生物学功能．就RNA干涉与基因沉默的研究历史、作用机制和应用作了综述．     

Regulation of microRNA on plant development and viral infection

THE FIRST MIRNA WAS IDENTIFIED IN C. ELEGANS AS EARLY AS IN 1993; THE IMPORTANCE OF MIRNAS, HOWEVER, IS RECOGNIZED ONLY RECENTLY AFTER THE DISCOVERY OF MIRNAS EXISTING UNIVERSALLY IN EUKARYOTIC ORGANISMS. THE SECOND MIRNA WAS IDENTIFIED IN 2000[1]. SINCE …     

AC2 and AC4 proteins of <Emphasis Type="Italic">Tomato yellow leaf curl China virus</Emphasis> and <Emphasis Type="Italic">Tobacco curly shoot virus</Emphasis> mediate suppression of RNA silencing

Tomato yellow leaf curl China virus Y10 isolate (TYLCCNV-Y10) alone could systemically infect host plants such as Nicotiana benthamiana without symptoms. In contrast, Tobacco curly shoot virus Y35 isolate (TbCSV-Y35) alone induces leaf curl symptoms in N. benthamiana. When inoculated into transgenic N. benthamiana plants expressing GFP gene (line 16c), TYLCCNV-Y10 neither reverses the established GFP silencing nor blocks the onset of GFP silencing. In contrast, TbCSV-Y35 can partially reverse the established GFP silencing and block the onset of GFP silencing in new leaves. In the patch co-infiltration assays, the AC2 and AC4 proteins of TYLCCNV-Y10 and TbCSV-Y35 could suppress local GFP silencing and delay systemic GFP silencing, suggesting that they are suppressors of RNA silencing. Comparison of the accumulation levels of GFP mRNA in the co-infiltration patches showed that Y10 AC2 and Y35 AC2 proteins had similar efficiency for suppression of RNA silencing. However, Y35 AC4 protein functioned as a stronger suppressor of RNA silencing than Y10 AC4 protein. There-fore, the pathogenicity difference between TbCSV-Y35 and TYLCCNV-Y10 may be related to the functional difference in their AC4 proteins.     

Suppressor of RNA silencing encoded by Rice gall dwarf virus genome segment 11

Rice gall dwarf virus （RGDV） is an important rice pathogen in China and Southeast Asia. However, little is known about the molecular mechanisms of RGDV interactions with plant cells. Here, we have identified an RGDV protein, Pns11, which acts as a suppressor of RNA silencing in coinfiltration assays with the reporter, green fluorescent protein （GFP）in transgenic Nicotiana benthamiana line 16c carrying GFP. Pns11 suppressed local and systemic silencing induced by sense RNA. The spread of mobile RNA silencing signals was blocked or inactivated by Pns11. Expression of Pns11 also enhanced Potato virus X pathogenicity in IV. benthamiana. This suppressor could reduce, but not eliminate, siRNA in the local and systemic RNA silencing suppression assays, suggesting that Pns11 functions by interfering with initial stages of RNA silencing.     

Delayed resistance to Cucumber mosaic virus mediated by 3’UTR-derived hairpin RNA

RNA silencing has been shown to function in the plant antivirus defense response, leading to viral RNA degradation induced by vsiRNA-containing RISC cleavage activity. Cucumber mosaic virus （CMV） 3′UTR sequences share a high conservation of nucleotide sequence and secondary structures that are important for CMV replication. Here, in an attempt to simultaneously target the multiple genomic and subgenomic RNAs of CMV for degradation, CMV 3′UTR were used to design hairpin RNA （hpRNA） to transform tobacco （Xanthi. nc） so as to constitutively produce viral siRNAs. Most of the transgenic plants expressing CMV Q strain （Q-CMV, subgroup Ⅱ strain） RNA3 3′UTR-derived hpRNA showed delayed resistance to Q-CMV infection and exhibited recovery phenotypes. Compared with Q-CMV-inoculated leaves, the upper leaves showed weak or no disease symptoms and a reduced accumulation level of viral RNAs. Together with transient assays, our results indicate that the 3′UTR-derived siRNAs were biologically active in targeting viral RNA for degradation. Recovery resistance in transgenic plants was also observed against subgroup IB strain SD-CMV infection, indicating a broad-spectrum anti-CMV effect of the 3′UTR-based antiviral silencing. Northern blot assays indicated that there was no strong correlation between the degree of resistance and the accumulation level of 3′UTR-derived siRNAs, suggesting that to target a highly structured RNA, such as the CMV 3′UTR, the quantity of siRNAs may not be the only determinant of silencing efficiency. Target RNA secondary structures may also affect target accessibility, siRNA-containing RISC-target recognition and the consequent antiviral effect.