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United States Department of Agriculture

Agricultural Research Service

Research Project: WHEAT STREAK MOSAIC VIRUS INTERACTIONS WITH HOST AND VECTOR Title: Wheat streak mosaic virus P1, not HC-Pro, facilitates disease synergism and suppression of post-transcriptional gene silencing

Authors
item Stenger, Drake
item Young, Brock
item Qu, Feng - UNIVERSITY OF NEBRASKA
item Morris, T. Jack - UNIVERSITY OF NEBRASKA
item French, Roy

Submitted to: American Phytopathological Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: May 15, 2007
Publication Date: August 1, 2007
Citation: Stenger, D.C., Young, B.A., Qu, F., Morris, T., French, R.C. 2007. Wheat streak mosaic virus P1, not HC-Pro, facilitates disease synergism and suppression of post-transcriptional gene silencing. Phytopathology 97:S111.

Interpretive Summary: Potyvirus HC-Pro is a suppressor of post-transcriptional gene silencing (PTGS). One consequence of PTGS suppression is pathogenicity enhancement, resulting in disease synergism upon mixed infection of a potyvirus and an unrelated virus. Tritimoviruses also encode HC-Pro sharing limited sequence identity with potyviruses, but it is not known if tritimovirus HC-Pro suppresses PTGS. Here, we report that a deletion derivative of the tritimovirus wheat streak mosaic virus (WSMV) isolate Sidney81 completely lacking HC-Pro remained competent to produce disease synergism in mixed infections with maize chlorotic mottle virus. Elevation of relative virus titers in mixed infections also was independent of WSMV HC-Pro. These results suggested that WSMV HC-Pro is not a suppressor of PTGS. Each of the nine WSMV-Sidney 81 coding regions were tested for suppression of PTGS using the standard agroinfiltration assay of transgenic Nicotiana benthamiana line 16C expressing GFP. P1 was the only WSMV-Sidney81 coding region to exhibit PTGS suppression activity. P1, but not HC-Pro, of two additional tritimoviruses (WSMV-El Batan 3 and Oat necrotic mottle virus) also suppressed PTGS. Furthermore, pathogenicity of Potato virus X (PVX) was enhanced when inoculated onto transgenic N. benthamiana plants expressing WSMV P1 relative to transgenic N. benthamiana plants expressing GFP or WSMV HC-Pro. Collectively, these results indicate that tritmoviruses and potyviruses utilize different genes to accomplish PTGS suppression and pathogenicity enhancement.

Technical Abstract: Potyvirus HC-Pro is a suppressor of post-transcriptional gene silencing (PTGS). One consequence of PTGS suppression is pathogenicity enhancement, resulting in disease synergism upon mixed infection of a potyvirus and an unrelated virus. Tritimoviruses also encode HC-Pro sharing limited sequence identity with potyviruses, but it is not known if tritimovirus HC-Pro suppresses PTGS. Here, we report that a deletion derivative of the tritimovirus wheat streak mosaic virus (WSMV) isolate Sidney81 completely lacking HC-Pro remained competent to produce disease synergism in mixed infections with maize chlorotic mottle virus. Elevation of relative virus titers in mixed infections also was independent of WSMV HC-Pro. These results suggested that WSMV HC-Pro is not a suppressor of PTGS. Each of the nine WSMV-Sidney 81 coding regions were tested for suppression of PTGS using the standard agroinfiltration assay of transgenic Nicotiana benthamiana line 16C expressing GFP. P1 was the only WSMV-Sidney81 coding region to exhibit PTGS suppression activity. P1, but not HC-Pro, of two additional tritimoviruses (WSMV-El Batan 3 and Oat necrotic mottle virus) also suppressed PTGS. Furthermore, pathogenicity of Potato virus X (PVX) was enhanced when inoculated onto transgenic N. benthamiana plants expressing WSMV P1 relative to transgenic N. benthamiana plants expressing GFP or WSMV HC-Pro. Collectively, these results indicate that tritmoviruses and potyviruses utilize different genes to accomplish PTGS suppression and pathogenicity enhancement.

Last Modified: 10/23/2014
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