斯里兰卡木薯花叶病毒AC2与拟南芥SGS3蛋白互作研究

Interactions Between Sri Lankan cassava mosaic virus AC2 and AtSGS3 Proteins

木薯花叶病毒病(cassava mosaic disease,CMD)对我国和世界木薯生产造成严重威胁和危害,目前尚无有效防治方法且缺乏抗性材料,造成严重经济损失,被认为是最有威胁性的病毒病之一,斯里兰卡木薯花叶病毒(Sri Lankan cassava mosaic virus,SLCMV)是引起木薯花叶病的主要病原之一。RNA沉默是植物和动物先天性的一种抗病毒免疫反应机制,寄主转录后基因沉默(post transcriptional gene silencing,PTGS)是真核生物中一种保守的基因表达调控机制,也是重要的抗病毒免疫机制之一。寄主基因沉默抑制子(suppressor of gene silencing 3,SGS3)是PTGS通路的关键蛋白,在寄主抵御病毒侵染中发挥着关键作用。为抵御宿主这种免疫反应,病毒通常编码病毒沉默抑制子(viral suppressors of RNA silencing,VSRs)来抵御寄主PTGS的病毒防御机制,与寄主蛋白互作是沉默抑制子发挥作用的主要作用机制之一。为探究SLCMV AC2是否通过与AtSGS3互作而抑制寄主PTGS的免疫功能,本研究采用酵母双杂交技术(yeast two hybrid system,Y2H)和双分子荧光互补技术(bimolecular fluorescence complementation,BiFC)分析SLCMV AC2与AtSGS3之间的相互作用。结果表明:SLCMV AC2与AtSGS3蛋白在酵母细胞和植物体内均存在相互作用的关系。亚细胞共定位研究进一步证明SLCMV AC2在与AtSGS3互作后,可与AtSGS3形成siRNA-body的RDR6发生共定位。这些结果表明SLCMV AC2可能通过与siRNA-body互作而影响寄主自身免疫机制,提高病毒致病性,SLCMV AC2与AtSGS3的互作可能是SLCMV侵染木薯导致花叶症状发生的分子基础。该研究结果为后续深入解析SLCMV致病机理提供新的理论依据。

Cassava mosaic disease(CMD)poses a serious threat and danger to cassava production in China and the world,and there is no effective control method and lack of resistant materials,causing serious economic losses,and is considered one of the most threatening viral diseases.Sri Lankan cassava mosaic virus(SLCMV)is one of the major pathogens causing cassava mosaic disease.RNA silencing is an innate antiviral immune response mechanism in plants and animals,and post transcriptional gene silencing(PTGS)is a conserved gene expression regulatory mechanism in eukaryotes,and is one of the important antiviral immune mechanisms.Suppressor of gene silencing 3(SGS3)is a key protein of the PTGS pathway and plays a critical role in host defense against viral invasion.To counteract this host immune response,viruses usually encode viral suppressors of RNA silencing(VSRs)to counteract the viral defense mechanism of host PTGS,and interaction with host proteins is one of the main mechanisms of action for the silencing suppressors to function.In order to investigate whether SLCMV AC2 inhibits the immune function of host PTGS by interacting with AtSGS3,we analyzed the immune function of host PTGS by using yeast two-hybrid(Y2H)system and bimolecular fluorescence complementation(BiFC)experiments,to analyze the interaction between AtSGS3 and SLCMV AC2.The results showed that SLCMV AC2 interacted with AtSGS3 protein in both yeast cells and plants.In subcellular co-localization experimental studies,we further demonstrated that SLCMV AC2 could co-localize with AtRDR6,a close partner of AtSGS3,after interacting with AtSGS3.The data suggest that SLCMV AC2 may affect the host autoimmune mechanism and enhance viral pathogenicity by interacting with siRNA-body,and that the interaction between SLCMV AC2 and AtSGS3 may be the molecular basis for the development of foliar symptoms in SLCMV-infected cassava,and the results of this study would provide a new theoretical basis for the subsequent in-depth analysis of the pathogenicity mechanism of SLCMV.