title: Effects of the crinivirus coat protein-interacting plant protein SAHH on post-transcriptional RNA silencing and its suppression.
abstract: In plants, post-transcriptional gene silencing (PTGS) is a sequence-specific mechanism of RNA degradation induced by double-stranded RNA (dsRNA), which is processed into small interfering RNAs (siRNAs). siRNAs are methylated and, thereby, stabilized by the activity of the S-adenosylmethionine-dependent RNA methyltransferase HEN1. PTGS is amplified by host-encoded RNA-dependent RNA polymerases (RDR), which generate dsRNA that is processed into secondary siRNAs. To counteract this RNA silencing-mediated response of the host, plant viruses express proteins with silencing suppression activity. Here, we report that the coat protein (CP) of crinivirus (family Closteroviridae, genus Crinivirus) Tomato chlorosis virus, a known suppressor of silencing, interacts with S-adenosylhomocysteine hydrolase (SAHH), a plant protein essential for sustaining the methyl cycle and S-adenosylmethionine-dependent methyltransferase activity. Our results show that, by contributing to an increased accumulation of secondary siRNAs generated by the action of RDR6, SAHH enhances local RNA silencing. Although downregulation of SAHH prevents local silencing, it enhances the spread of systemic silencing. Our results also show that SAHH is important in the suppression of local RNA silencing not only by the crinivirus Tomato chlorosis virus CP but also by the multifunctional helper component-proteinase of the potyvirus Potato virus Y.
authors.affiliation: Instituto de Hortofruticultura Subtropical y Mediterránea La Mayora, Universidad de Málaga-Consejo Superior de Investigaciones Científicas IHSM-UMA-CSIC, Estación Experimental La Mayora, Málaga, Spain.
authors.forename: M Carmen
authors.initials: MC
authors.lastname: Cañizares
authors.forename: Rosa
authors.initials: R
authors.lastname: Lozano-Durán
authors.forename: Tomás
authors.initials: T
authors.lastname: Canto
authors.forename: Eduardo R
authors.initials: ER
authors.lastname: Bejarano
authors.forename: David M
authors.initials: DM
authors.lastname: Bisaro
authors.forename: Jesús
authors.initials: J
authors.lastname: Navas-Castillo
authors.forename: Enrique
authors.initials: E
authors.lastname: Moriones
mesh_terms: D043383:Adenosylhomocysteinase / Q000235:genetics / Q000378:metabolism*; D036022:Capsid Proteins / Q000235:genetics / Q000378:metabolism*; D029383:Crinivirus / Q000502:physiology*; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism; D015536:Down-Regulation; D018506:Gene Expression Regulation, Plant; D054884:Host-Pathogen Interactions; D008745:Methylation; D010935:Plant Diseases / Q000276:immunology* / Q000821:virology; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics / Q000276:immunology / Q000821:virology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D017800:Potyvirus / Q000502:physiology; D034622:RNA Interference; D018749:RNA, Plant / Q000235:genetics; D012367:RNA, Viral / Q000235:genetics / Q000378:metabolism; D014026:Nicotiana / Q000201:enzymology* / Q000235:genetics / Q000276:immunology / Q000821:virology; D020798:Two-Hybrid System Techniques; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D036022:Capsid Proteins; D010940:Plant Proteins; D018749:RNA, Plant; D012367:RNA, Viral; D014764:Viral Proteins; D043383:Adenosylhomocysteinase; D003546:Cysteine Endopeptidases; C072775:HC-Pro protein, potyvirus