title: Differential expression of cucumber RNA-dependent RNA polymerase 1 genes during antiviral defence and resistance.
abstract: RNA-dependent RNA polymerase 1 (RDR1) plays a crucial role in plant defence against viruses. In this study, it was observed that cucumber, Cucumis sativus, uniquely encodes a small gene family of four RDR1 genes. The cucumber RDR1 genes (CsRDR1a, CsRDR1b and duplicated CsRDR1c1/c2) shared 55%-60% homology in their encoded amino acid sequences. In healthy cucumber plants, RDR1a and RDR1b transcripts were expressed at higher levels than transcripts of RDR1c1/c2, which were barely detectable. The expression of all four CsRDR1 genes was induced by virus infection, after which the expression level of CsRDR1b increased 10-20-fold in several virus-resistant cucumber cultivars and in a broad virus-resistant transgenic cucumber line expressing a high level of transgene small RNAs, all without alteration in salicylic acid (SA) levels. By comparison, CsRDR1c1/c2 genes were highly induced (25-1300-fold) in susceptible cucumber cultivars infected with RNA or DNA viruses. Inhibition of RDR1c1/c2 expression led to increased virus accumulation. Ectopic application of SA induced the expression of cucumber RDR1a, RDR1b and RDRc1/c2 genes. A constitutive high level of RDR1b gene expression independent of SA was found to be associated with broad virus resistance. These findings show that multiple RDR1 genes are involved in virus resistance in cucumber and are regulated in a coordinated fashion with different expression profiles.
authors.affiliation: Department of Plant Pathology and Weed Research, Agricultural Research Organization, Volcani Center, Bet Dagan, 50250, Israel.
authors.forename: Diana
authors.initials: D
authors.lastname: Leibman
authors.affiliation: Department of Plant Pathology and Weed Research, Agricultural Research Organization, Volcani Center, Bet Dagan, 50250, Israel.
authors.forename: Michael
authors.initials: M
authors.lastname: Kravchik
authors.affiliation: Department of Vegetable and Field Crops, Agricultural Research Organization, Volcani Center, Bet Dagan, 50250, Israel.
authors.forename: Dalia
authors.initials: D
authors.lastname: Wolf
authors.affiliation: Department of Plant Pathology and Weed Research, Agricultural Research Organization, Volcani Center, Bet Dagan, 50250, Israel.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Haviv
authors.affiliation: Department of Fruit Tree Sciences, Agricultural Research Organization, Volcani Center, Bet Dagan, 50250, Israel.
authors.forename: Mira
authors.initials: M
authors.lastname: Weissberg
authors.affiliation: Department of Fruit Tree Sciences, Agricultural Research Organization, Volcani Center, Bet Dagan, 50250, Israel.
authors.forename: Ron
authors.initials: R
authors.lastname: Ophir
authors.affiliation: Department of Vegetable Crops and Plant Genetics, Agricultural Research Organization, Newe Ya'ar Research Center, PO Box 1021, Ramat, Yishay, 30-095, Israel.
authors.forename: Harry S
authors.initials: HS
authors.lastname: Paris
authors.affiliation: Department of Horticultural Sciences, Seoul Women's University, Nowon-gu, Seoul, 01797, South Korea.
authors.forename: Peter
authors.initials: P
authors.lastname: Palukaitis
authors.affiliation: Department of Plant Pathology and Microbiology & Institute for Integrative Genome Biology, University of California, Riverside, CA, 92521, USA.
authors.forename: Shou-Wei
authors.initials: SW
authors.lastname: Ding
authors.affiliation: Department of Plant Pathology and Weed Research, Agricultural Research Organization, Volcani Center, Bet Dagan, 50250, Israel.
authors.forename: Victor
authors.initials: V
authors.lastname: Gaba
authors.affiliation: Department of Plant Pathology and Weed Research, Agricultural Research Organization, Volcani Center, Bet Dagan, 50250, Israel.
authors.forename: Amit
authors.initials: A
authors.lastname: Gal-On
mesh_terms: D018553:Cucumis sativus / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism*; D012324:RNA-Dependent RNA Polymerase / Q000235:genetics / Q000378:metabolism*; D020156:Salicylic Acid / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D012324:RNA-Dependent RNA Polymerase; D020156:Salicylic Acid
keywords: RDR1; cucumber; gene expression; silencing; virus resistance