Table 1

Suppression of PTGS of GFP mRNA caused by various plant viruses

Virus groupVirusSuppression of PTGSOld leaves/New leavesWhole leaf/Vein centricProtein*Other known functions
ComovirusCpMV5/6OL and NLVein centric?
CucumovirusCMV20/20NL onlyWhole Leaf2bHost-specific long distance movement
GeminivirusACMV6/6OL and NLWhole leafAC2Virion sense gene expression transactivator
NMV8/9OL and NLWhole leaf?
NVX7/9OL and NLWhole leaf?
VMV7/9OL and NLWhole leaf?
PotyvirusPVY/TEV10/10OL and NLWhole leafHcProGenome amplification
TEVViral synergism
Long distance movement
Polyprotein processing
Aphid transmission
SobemovirusRYMVP1Virus accumulation
Long distance movement
TobamovirusTMV4/6OL and NLVein centric?
TobravirusTRV7/9OL and NLWhole leaf?
TombusvirusTBSV7/9NL onlyVein centric19KHost-specific spread and symptom determinant
  • PTGS of the GFP mRNA was induced in transgenic N. benthamiana by Agrobacterium infiltration, as described (17). After systemic infection, suppression of gene silencing was assessed under UV illumination over time and confirmed by RNA gel blot analysis. RNA samples were taken from either old leaves that had emerged before the virus had spread systemically (OL) or new leaves emerging after virus infection (NL). The total number of plants tested is indicated as well as the phenotype of suppression in leaves (affecting whole tissues or vein centric). Viruses were tested in duplicate independent experiments during the summer and the winter. 

  • * The identification of the 2b protein and HcPro as PTGS suppressors is described in refs. 1113. The identification of AC2, P1, and the 19K protein as PTGS suppressors is described in this study. 

  • Appropriate references can be found in refs. 16 (2b), 21 (AC2), 13 and 15 (HcPro), 24 (P1), and 22 [19K (19-kDa)]. 

  • RYMV is not infectious in N. benthamiana. The P1 protein has been identified as a PTGS suppressor by expression from the PVX vector.