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Open AccessArticle

The Luteovirus P4 Movement Protein Is a Suppressor of Systemic RNA Silencing

1
School of Life and Environmental Sciences, University of Sydney, Sydney, NSW 2006, Australia
2
Plant Industry Division, CSIRO, P.O. Box 1600, Canberra, ACT 2601, Australia
3
Department of Virology (M.F.S.V.), Department of Genetics (R.L.C.) and Institute of Medical Biochemistry (A.F.F.), Federal University of Rio de Janeiro (UFRJ), Rio de Janeiro 21941-590, Brazil
4
North Florida Research and Education Center, University of Florida, Quincy, FL 32351, USA
5
Department of Agriculture and Agri-Food Canada, Lethbridge, AB T1J4B1, Canada
6
School of Earth, Environmental and Biological sciences, Queensland University of Technology, Brisbane, QLD 4001, Australia
*
Authors to whom correspondence should be addressed.
Viruses 2017, 9(10), 294; https://doi.org/10.3390/v9100294
Received: 25 September 2017 / Revised: 4 October 2017 / Accepted: 6 October 2017 / Published: 10 October 2017
(This article belongs to the Section Viruses of Plants, Fungi and Protozoa)
The plant viral family Luteoviridae is divided into three genera: Luteovirus, Polerovirus and Enamovirus. Without assistance from another virus, members of the family are confined to the cells of the host plant’s vascular system. The first open reading frame (ORF) of poleroviruses and enamoviruses encodes P0 proteins which act as silencing suppressor proteins (VSRs) against the plant’s viral defense-mediating RNA silencing machinery. Luteoviruses, such as barley yellow dwarf virus-PAV (BYDV-PAV), however, have no P0 to carry out the VSR role, so we investigated whether other proteins or RNAs encoded by BYDV-PAV confer protection against the plant’s silencing machinery. Deep-sequencing of small RNAs from plants infected with BYDV-PAV revealed that the virus is subjected to RNA silencing in the phloem tissues and there was no evidence of protection afforded by a possible decoy effect of the highly abundant subgenomic RNA3. However, analysis of VSR activity among the BYDV-PAV ORFs revealed systemic silencing suppression by the P4 movement protein, and a similar, but weaker, activity by P6. The closely related BYDV-PAS P4, but not the polerovirus potato leafroll virus P4, also displayed systemic VSR activity. Both luteovirus and the polerovirus P4 proteins also showed transient, weak local silencing suppression. This suggests that systemic silencing suppression is the principal mechanism by which the luteoviruses BYDV-PAV and BYDV-PAS minimize the effects of the plant’s anti-viral defense. View Full-Text
Keywords: Luteoviridae; Luteovirus; Polerovirus; RNA silencing suppression Luteoviridae; Luteovirus; Polerovirus; RNA silencing suppression
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Fusaro, A.F.; Barton, D.A.; Nakasugi, K.; Jackson, C.; Kalischuk, M.L.; Kawchuk, L.M.; Vaslin, M.F.S.; Correa, R.L.; Waterhouse, P.M. The Luteovirus P4 Movement Protein Is a Suppressor of Systemic RNA Silencing. Viruses 2017, 9, 294.

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