ARS | Publication request: Wheat streak mosaic virus lacking HC-Pro is competent to produce disease synergism in mixed infections with Maize chlorotic mottle virus

Submitted to: American Society for Virology Meeting
Publication Type: Abstract Only
Publication Acceptance Date: March 1, 2007
Publication Date: July 15, 2007
Citation: Stenger, D.C., Young, B.A., Qu, F., Morris, T., French, R.C. 2007. Wheat streak mosaic virus lacking HC-Pro is competent to produce disease synergism in mixed infections with Maize chlorotic mottle virus. American Society for Virology, 26th Annual Meeting, Corvallis, OR, July 2007 (abstracts of meeting not published).

Technical Abstract: Single infections of maize plants with the tritimovirus Wheat streak mosaic virus (WSMV) or the machlomovirus Maize chlorotic mottle virus (MCMV) are characterized by systemic chlorosis but not necrosis. Co-infection of maize with both viruses results in disease synergism and induction of corn lethal necrosis disease (CLND). Here, we report that a WSMV construct, in which the HC-Pro coding region was completely deleted, was equally effective as WSMV encoding HC-Pro in producing CLND in mixed infections with MCMV. These results indicated that, unlike potyvirus HC-Pro, WSMV HC-Pro was dispensable for pathogenicity enhancement. Elevated viral titers, commonly observed in mixed infections relative to single infections, also were observed regardless of whether or not HC-Pro was encoded by the WSMV construct paired with MCMV. MCMV titer was increased in mixed infections with WSMV up to 2-fold two weeks post inoculation and up to 4-fold one month post inoculation. Titer of WSMV in mixed infections with MCMV was increased 3- to 6-fold two weeks post inoculation but was not elevated in mixed infections one month post inoculation. We further demonstrated that WSMV HC-Pro did not suppress post-transcriptional gene silencing (PTGS) using a Agrobacterium-mediated co-infiltration assay in which potyvirus HC-Pro acts as a strong suppressor of PTGS. Collectively, the results define significant differences in HC-Pro function among divergent genera of the family Potyviridae and suggest that the tritimovirus WSMV utilizes a gene other than HC-Pro to suppress PTGS and mediate synergistic interactions with unrelated viruses in mixed infections.