Title: Loss-of-Susceptibility Mutants of Arabidopsis thaliana Reveal an Essential Role for eIF(iso)4E during Potyvirus Infection
Abstract: The Arabidopsis thaliana-potyvirus system was developed to identify compatibility and incompatibility factors involved during infection and disease caused by positive-strand RNA viruses [1Whitham S Yamamoto M Carrington J.C Selectable viruses and Arabidopsis thaliana gain-of-susceptibility mutants.Proc. Natl. Acad. Sci. USA. 1999; 96: 772-777Crossref PubMed Scopus (73) Google Scholar, 2Mahajan S.K Chisholm S.T Whitham S Carrington J.C Identification and characterization of a locus (RTM1) in Arabidopsis thaliana that restricts long-distance movement of tobacco etch virus.Plant J. 1998; 14: 177-186Crossref PubMed Scopus (103) Google Scholar]. Several Arabidopsis mutants with increased susceptibility to Tobacco etch potyvirus (TEV) were isolated previously [1Whitham S Yamamoto M Carrington J.C Selectable viruses and Arabidopsis thaliana gain-of-susceptibility mutants.Proc. Natl. Acad. Sci. USA. 1999; 96: 772-777Crossref PubMed Scopus (73) Google Scholar], revealing a virus-specific resistance system in the phloem [3Chisholm S.T Parra M.A Anderberg R.J Carrington J.C Arabidopsis RTM1 and RTM2 genes function in phloem to restrict long-distance movement of tobacco etch virus.Plant Physiol. 2001; 127: 1667-1675Crossref PubMed Scopus (133) Google Scholar, 4Chisholm S.T Mahajan S.K Whitham S.A Yamamoto M.L Carrington J.C Cloning of the Arabidopsis RTM1 gene, which controls restriction of long-distance movement of tobacco etch virus.Proc. Natl. Acad. Sci. USA. 2000; 97: 489-494Crossref PubMed Scopus (166) Google Scholar, 5Whitham S.A Anderberg R.J Chisholm S.T Carrington J.C Arabidopsis RTM2 gene is necessary for specific restriction of tobacco etch virus and encodes an unusual small heat shock-like protein.Plant Cell. 2000; 12: 569-582PubMed Google Scholar]. In this study, Arabidopsis mutants with decreased susceptibility to Turnip mosaic potyvirus (TuMV) were isolated. Three independent mutants that conferred immunity to TuMV were isolated and assigned to the same complementation group. These mutants were also immune or near-immune to TEV but were susceptible to an unrelated virus. The locus associated with decreased susceptibility was named loss-of-susceptibility to potyviruses 1 (lsp1). The LSP1 locus was isolated by map-based cloning and was identified as the gene encoding translation factor eIF(iso)4E, one of several known Arabidopsis isoforms that has cap binding activity. eIF4E and eIF(iso)4E from different plant species were shown previously to interact with the genome-linked protein (VPg) of TEV and TuMV, respectively. Models to explain the roles of eIF(iso)4E during virus infection are presented.