Expression of artificial microRNAs in tomato confers efficient and stable virus resistance in a cell-autonomous manner
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Expression of artificial microRNAs (amiRNAs) in plants can target and degrade the invading viral RNA, consequently conferring virus resistance. Two amiRNAs, targeting the coding sequence shared by the 2a and 2b genes and the highly conserved 3′ untranslated region (UTR) of Cucumber mosaic virus (CMV), respectively, were generated and introduced into the susceptible tomato. The transgenic tomato plants expressing amiRNAs displayed effective resistance to CMV infection and CMV mixed with non-targeted viruses, including tobacco mosaic virus and tomato yellow leaf curl virus. A series of grafting assays indicate scions originated from the transgenic tomato plant maintain stable resistance to CMV infection after grafted onto a CMV-infected rootstock. However, the grafting assay also suggests that the amiRNA-mediated resistance acts in a cell-autonomous manner and the amiRNA signal cannot be transmitted over long distances through the vascular system. Moreover, transgenic plants expressing amiRNA targeting the 2a and 2b viral genes displayed slightly more effective to repress CMV RNA accumulation than transgenic plants expressing amiRNA targeting the 3′ UTR of viral genome did. Our work provides new evidence of the use of amiRNAs as an effective approach to engineer viral resistance in the tomato and possibly in other crops.
KeywordsArtificial miRNA Anti-virus Cucumber mosaic virus Tomato Cell-autonomous Mixed infection
We thank to Prof. Rongxiang Fang (State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China) for providing CMV-SD for plant viral challenge and Miss Maria Nussbaum for critical reading of the manuscript. This work was supported by grants from the 973 Program (No. 2009CB119000) and NSFC (No. 30671417), and 863 Program (No. 2007AA10Z131).