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Scottish Crop Research Institute

Proc. Natl. Acad. Sci. USA, Published online before print June 18, 2007 Interaction of a plant virus-encoded protein with the major nucleolar protein fibrillarin is required for systemic virus infection

Abstract

( Cajal bodies | plant virus movement | ribonucleoprotein particles )

Sang Hyon Kim ${dagger}$ , Stuart MacFarlane ${dagger}$ , Natalia O. Kalinina ${dagger}$ ${ddagger}$ , Daria V. Rakitina ${dagger}$ ${ddagger}$ , Eugene V. Ryabov ${sect}$ , Trudi Gillespie ${dagger}$ , Sophie Haupt ${dagger}$ , John W. S. Brown ${dagger}$ , and Michael Taliansky ${dagger}$ ¶

Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, United Kingdom; A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119992, Russia; and Horticulture Research International, University of Warwick, Wellesbourne, Warwick CV35 9EF, United Kingdom

Communicated by Bryan D. Harrison, Scottish Crop Research Institute,Dundee, United Kingdom, May 17, 2007 (received for review April4, 2007)

The nucleolus and specific nucleolar proteins are involved in the life cycles of some plant and animal viruses, but the functions of these proteins and of nucleolar trafficking in virus infections are largely unknown. The ORF3 protein of the plant virus, groundnut rosette virus (an umbravirus), has been shown to cycle through the nucleus, passing through Cajal bodies to the nucleolus and then exiting back into the cytoplasm. This journey is absolutely required for the formation of viral ribonucleoprotein particles (RNPs) that, themselves, are essential for the spread of the virus to noninoculated leaves of the shoot tip. Here, we show that these processes rely on the interaction of the ORF3 protein with fibrillarin, a major nucleolar protein. Silencing of the fibrillarin gene prevents long-distance movement of groundnut rosette virus but does not affect viral replication or cell-to-cell movement. Repressing fibrillarin production also localizes the ORF3 protein to multiple Cajal body-like aggregates that fail to fuse with the nucleolus. Umbraviral ORF3 protein and fibrillarin interact in vitro and, when mixed with umbravirus RNA, form an RNP complex. This complex has a filamentous structure with some regular helical features, resembling the RNP complex formed in vivo during umbravirus infection. The filaments formed in vitro are infectious when inoculated to plants, and their infectivity is resistant to RNase. These results demonstrate previously undescribed functions for fibrillarin as an essential component of translocatable viral RNPs and may have implications for other plant and animal viruses that interact with the nucleolus.

Author contributions: S.H.K., S.M., N.O.K., J.W.S.B., and M.T. designed research; S.H.K., S.M., D.V.R., E.V.R., T.G., and S.H. performed research; S.H.K., N.O.K., D.V.R., J.W.S.B., and M.T. analyzed data; and S.H.K., J.W.S.B., and M.T. wrote the paper.

The authors declare no conflict of interest.

^¶To whom correspondence should be addressed.

논문정보

형식Research article
게재일2007년 06월 (BRIC 등록일 )
연구진국외 연구진
분야 생명과학 > 식물학

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