Submitted to: Virus Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 25, 2011
Publication Date: February 3, 2012
Repository URL: http://handle.nal.usda.gov/10113/55916
Citation: Young, B.A., Stenger, D.C., Ou, F., Morris, T., Tatineni, S., French, R.C. 2012. Tritimovirus P1 functions as a suppressor of RNA silencing and an enhancer of disease symptoms. Virus Research. 163: 672-677. Interpretive Summary: Plants have developed several means to defend against viral infections. A major defense mechanism is termed “RNA silencing”, or more generally “PTGS”. Plant viruses in turn have evolved specific proteins to counter this defense. How wheat streak mosaic virus (WSMV), the most economically important virus in wheat in the Great Plains, evades host defenses was not known. In this study we identified WSMV P1 protein as the suppressor of PTGS and show that related mite-transmitted viruses in the potyvirus genus Tritimovirus defend against PTGS the same way. However, mite-transmitted viruses in the potyvirus genus Rymovirus have a different suppressor protein. We further demonstrated that WSMV P1 is can exacerbate disease symptoms caused by a second virus. These results provide new insight into how WSMV causes disease and identifies P1 as a primary target for developing future molecular-based methods to control WSMV. Lastly, our results can be used to shed light on the evolutionary history of the largest group of plant viruses, the potyviruses.
Technical Abstract: Wheat streak mosaic virus (WSMV) is an eriophyid mite-transmitted virus of the genus Tritimovirus, family Potyviridae. Complete deletion of HC-Pro has no effect on WSMV virulence or disease synergism, suggesting that a different viral protein suppresses post-transcriptional gene silencing (PTGS). PTGS suppression assays using Nicotiana benthamiana 16C plants expressing GFP were conducted with each WSMV protein; only P1 suppressed PTGS. Symptom enhancement assays were conducted by inoculating Potato virus X (PVX) onto transgenic N. benthamiana. Symptoms produced by PVX were more severe on transgenic plants expressing WSMV P1 or potyvirus HC-Pro compared to transgenic plants expressing GFP or WSMV HC-Pro.