title: Expression of an extracellular ribonuclease gene increases resistance to Cucumber mosaic virus in tobacco.
abstract: BACKGROUND
  The apoplast plays an important role in plant defense against pathogens. Some extracellular PR-4 proteins possess ribonuclease activity and may directly inhibit the growth of pathogenic fungi. It is likely that extracellular RNases can also protect plants against some viruses with RNA genomes. However, many plant RNases are multifunctional and the direct link between their ribonucleolytic activity and antiviral defense still needs to be clarified. In this study, we evaluated the resistance of Nicotiana tabacum plants expressing a non-plant single-strand-specific extracellular RNase against Cucumber mosaic virus.
  
  
  RESULTS
  Severe mosaic symptoms and shrinkage were observed in the control non-transgenic plants 10 days after inoculation with Cucumber mosaic virus (CMV), whereas such disease symptoms were suppressed in the transgenic plants expressing the RNase gene. In a Western blot analysis, viral proliferation was observed in the uninoculated upper leaves of control plants, whereas virus levels were very low in those of transgenic plants. These results suggest that resistance against CMV was increased by the expression of the heterologous RNase gene.
  
  
  CONCLUSIONS
  We have previously shown that tobacco plants expressing heterologous RNases are characterized by high resistance to Tobacco mosaic virus. In this study, we demonstrated that elevated levels of extracellular RNase activity resulted in increased resistance to a virus with a different genome organization and life cycle. Thus, we conclude that the pathogen-induced expression of plant apoplastic RNases may increase non-specific resistance against viruses with RNA genomes.
authors.affiliation: Graduate School of Agricultural Science, Tohoku University, Sendai, 981-8555, Japan.
authors.forename: Teppei
authors.initials: T
authors.lastname: Sugawara
authors.affiliation: Institute of Cytology and Genetics, SB RAS, Novosibirsk, 630090, Russia.
authors.forename: Ekaterina A
authors.initials: EA
authors.lastname: Trifonova
authors.affiliation: Institute of Cytology and Genetics, SB RAS, Novosibirsk, 630090, Russia. ak@bionet.nsc.ru.|Novosibirsk State University, Novosibirsk, 630090, Russia. ak@bionet.nsc.ru.
authors.forename: Alex V
authors.initials: AV
authors.lastname: Kochetov
authors.affiliation: Graduate School of Agricultural Science, Tohoku University, Sendai, 981-8555, Japan. yoshinori.kanayama.a7@tohoku.ac.jp.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Kanayama
mesh_terms: D000818:Animals; D017799:Cucumovirus / Q000502:physiology*; D060467:Disease Resistance / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D057865:Plant Immunity / Q000235:genetics*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000821:virology; D012259:Ribonuclease, Pancreatic / Q000235:genetics* / Q000378:metabolism; D014026:Nicotiana / Q000235:genetics* / Q000821:virology*
chemical_list: D012259:Ribonuclease, Pancreatic
keywords: Apoplast; Plants; RNA viruses; RNases; Resistance