title: Crude extracts of bacterially expressed dsRNA can be used to protect plants against virus infections.
abstract: BACKGROUND
  Double-stranded RNA (dsRNA) is a potent initiator of gene silencing in a diverse group of organisms that includes plants, Caenorhabditis elegans, Drosophila and mammals. We have previously shown and patented that mechanical inoculation of in vitro-transcribed dsRNA derived from viral sequences specifically prevents virus infection in plants. The approach required the in vitro synthesis of large amounts of RNA involving high cost and considerable labour.
  
  
  RESULTS
  We have developed an in vivo expression system to produce large amounts of virus-derived dsRNAs in bacteria, with a view to providing a practical control of virus diseases in plants. Partially purified bacterial dsRNAs promoted specific interference with the infection in plants by two viruses belonging to the tobamovirus and potyvirus groups. Furthermore, we have demonstrated that easy to obtain, crude extracts of bacterially expressed dsRNAs are equally effective protecting plants against virus infections when sprayed onto plant surfaces by a simple procedure. Virus infectivity was significantly abolished when plants were sprayed with French Press lysates several days before virus inoculation.
  
  
  CONCLUSIONS
  Our approach provides an alternative to genetic transformation of plant species with dsRNA-expressing constructs capable to interfere with plant viruses. The main advantage of this mode of dsRNA production is its simplicity and its extremely low cost compared with the requirements for regenerating transgenic plants. This approach provides a reliable and potential tool, not only for plant protection against virus diseases, but also for the study of gene silencing mechanisms in plant virus infections.
authors.affiliation: Departamento de Biología de Plantas, Centro de Investigaciones Biológicas, CSIC, Velázquez 144, Madrid 28006, Spain. tenllado@cib.csic.es
authors.forename: Francisco
authors.initials: F
authors.lastname: Tenllado
authors.forename: Belén
authors.initials: B
authors.lastname: Martínez-García
authors.forename: Marisol
authors.initials: M
authors.lastname: Vargas
authors.forename: José Ramón
authors.initials: JR
authors.lastname: Díaz-Ruíz
mesh_terms: D045424:Complex Mixtures / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics; D020868:Gene Silencing; D005814:Genes, Viral / Q000235:genetics*; D007218:Industrial Microbiology / Q000191:economics / Q000379:methods; D010935:Plant Diseases / Q000821:virology; D010942:Plant Viruses / Q000187:drug effects* / Q000235:genetics; D010944:Plants / Q000821:virology; D034622:RNA Interference; D012330:RNA, Double-Stranded / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology*; D014779:Virus Replication / Q000187:drug effects*
chemical_list: D045424:Complex Mixtures; D012330:RNA, Double-Stranded