title: Suppression of post-transcriptional gene silencing by a plant viral protein localized in the nucleus.
abstract: Post-transcriptional gene silencing (PTGS) is a homology-dependent RNA degradation process that may target RNA exclusively in the cytoplasm. In plants, PTGS functions as a natural defense mechanism against viruses. We reported previously that the 2b protein encoded by cucumber mosaic cucumovirus (CMV) is a virulence determinant and a suppressor of PTGS initiation in transgenic Nicotiana benthamiana. By fusion with the green fluorescent protein, we now show that the CMV 2b protein localizes to the nuclei of tobacco suspension cells and whole plants via an arginine-rich nuclear localization signal, (22)KRRRRR(27). We further demonstrate that the nuclear targeting of the 2b protein is required for the efficient suppression of PTGS, indicating that PTGS may be blocked in the nucleus. In addition, our data indicate that the PTGS suppressor activity is important, but not sufficient, for virulence determination by the 2b protein.
authors.affiliation: Molecular Virology Laboratory, Institute of Molecular Agrobiology, The National University of Singapore, 1 Research Link, Singapore 117604.
authors.forename: A P
authors.initials: AP
authors.lastname: Lucy
authors.forename: H S
authors.initials: HS
authors.lastname: Guo
authors.forename: W X
authors.initials: WX
authors.lastname: Li
authors.forename: S W
authors.initials: SW
authors.lastname: Ding
mesh_terms: D000595:Amino Acid Sequence; D002467:Cell Nucleus / Q000378:metabolism / Q000821:virology; D017799:Cucumovirus / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity; D020868:Gene Silencing; D017343:Genes, Plant; D005814:Genes, Viral; D008969:Molecular Sequence Data; D030821:Plants, Genetically Modified; D010947:Plants, Toxic; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013489:Suppression, Genetic; D014026:Nicotiana / Q000235:genetics* / Q000821:virology*; D014764:Viral Proteins / Q000235:genetics* / Q000378:metabolism*; D014774:Virulence / Q000235:genetics
chemical_list: D018749:RNA, Plant; D011993:Recombinant Fusion Proteins; D014764:Viral Proteins