Silencing suppressor activity of the Tobacco rattle virus-encoded 16-kDa protein and interference with endogenous small RNA-guided regulatory pathways.
Higher plants use RNA silencing as a defense mechanism against viral infections, but viruses may encode suppressor proteins that counteract these defenses. Several virus-encoded suppressors also exert an inhibitory effect on endogenous small RNA regulatory pathways. Here we characterized the Tobacco rattle virus-encoded 16-kDa (TRV-16K) protein as a suppressor that blocked local RNA silencing induced by single (s)- and double-stranded (ds) RNA, indicating that TRV-16K interfered with a step in the silencing pathway downstream of dsRNA formation. The suppressor activity of TRV-16K was severely compromised by moderate to high dosages of dsRNA inducer. When silencing was locally triggered by ssRNA or low levels of dsRNA, silencing suppression by TRV-16K was associated with reduced accumulation of silencing-related siRNAs. TRV-16K also prevented partially cell-to-cell movement and systemic propagation of silencing but not transitive amplification of RNA silencing. We showed that neither TRV nor TRV-16K caused a global deregulation of the microRNA-regulatory pathway in Arabidopsis, suggesting that interference with microRNA biology was not a prerequisite for TRV, and probably many other plant viruses, to develop systemic infections in plants.
Martínez-Priego
Llucia
L
Departamento de Biología de Plantas, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Ramiro de Maeztu 9, 28040 Madrid, Spain. llucimarpri@cib.csic.es
Donaire
Livia
L
Barajas
Daniel
D
Llave
César
C
D017360:Arabidopsis / Q000276:immunology / Q000378:metabolism / Q000821:virology; D015536:Down-Regulation; D008970:Molecular Weight; D010942:Plant Viruses / Q000737:chemistry* / Q000502:physiology*; D030821:Plants, Genetically Modified; D034622:RNA Interference; D012328:RNA Viruses / Q000737:chemistry* / Q000502:physiology*; D018749:RNA, Plant / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D015398:Signal Transduction; D014026:Nicotiana / Q000276:immunology / Q000378:metabolism / Q000821:virology; D014764:Viral Proteins / Q000737:chemistry / Q000502:physiology*
D018749:RNA, Plant; D034741:RNA, Small Interfering; D014764:Viral Proteins