The type-1 and type-2 ribosome-inactivating proteins from Iris confer transgenic tobacco plants local but not systemic protection against viruses.
The antiviral activity of the type-2 ribosome-inactivating protein (RIP) IRAb from Iris was analyzed by expressing IRAb in tobacco (Nicotiana tabacum L. cv. Samsun NN) plants and challenging the transgenic plants with tobacco mosaic virus (TMV). Although constitutive expression of IRAb resulted in an aberrant phenotype, the plants were fertile. Transgenic tobacco lines expressing IRAb showed a dose-dependent enhanced resistance against TMV infection but the level of protection was markedly lower than in plants expressing IRIP, the type-1 RIP from Iris that closely resembles the A-chain of IRAb. To verify whether IRIP or IRAb can also confer systemic protection against viruses, transgenic RIP-expressing scions were grafted onto control rootstocks and leaves of the rootstocks challenged with tobacco etch virus (TEV). In spite of the strong local antiviral effect of IRIP and IRAb the RIPs could not provide systemic protection against TEV. Hence our results demonstrate that expression of the type-1 and type-2 RIPs from Iris confers tobacco plants local protection against two unrelated viruses. The antiviral activity of both RIPs was not accompanied by an induction of pathogenesis-related proteins. It is suggested that the observed antiviral activity of both Iris RIPs relies on their RNA N-glycohydrolase activity towards TMV RNA and plant rRNA.
Laboratory for Phytopathology and Plant Protection, Katholieke Universiteit Leuven, Willem de Croylaan 42, 3001 Leuven, Belgium.
Frank
F
Vandenbussche
Willy J
WJ
Peumans
Stijn
S
Desmyter
Paul
P
Proost
Marialibera
M
Ciani
Els J M
EJ
Van Damme
D004198:Disease Susceptibility; D031323:Iris Plant / Q000502:physiology*; D009699:N-Glycosyl Hydrolases / Q000235:genetics / Q000502:physiology*; D010641:Phenotype; D010935:Plant Diseases / Q000821:virology; D037121:Plant Lectins / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics / Q000502:physiology*; D010942:Plant Viruses / Q000276:immunology; D030821:Plants, Genetically Modified; D054788:Ribosome Inactivating Proteins; D054789:Ribosome Inactivating Proteins, Type 1; D054790:Ribosome Inactivating Proteins, Type 2; D014026:Nicotiana / Q000235:genetics* / Q000254:growth & development / Q000276:immunology / Q000821:virology
C086197:Iris lectin; D037121:Plant Lectins; D010940:Plant Proteins; D054789:Ribosome Inactivating Proteins, Type 1; D054790:Ribosome Inactivating Proteins, Type 2; D009699:N-Glycosyl Hydrolases; D054788:Ribosome Inactivating Proteins