title: Influence of host chloroplast proteins on Tobacco mosaic virus accumulation and intercellular movement.
abstract: Tobacco mosaic virus (TMV) forms dense cytoplasmic bodies containing replication-associated proteins (virus replication complexes [VRCs]) upon infection. To identify host proteins that interact with individual viral components of VRCs or VRCs in toto, we isolated viral replicase- and VRC-enriched fractions from TMV-infected Nicotiana tabacum plants. Two host proteins in enriched fractions, ATP-synthase γ-subunit (AtpC) and Rubisco activase (RCA) were identified by matrix-assisted laser-desorption ionization time-of-flight mass spectrometry or liquid chromatography-tandem mass spectrometry. Through pull-down analysis, RCA bound predominantly to the region between the methyltransferase and helicase domains of the TMV replicase. Tobamovirus, but not Cucumber mosaic virus or Potato virus X, infection of N. tabacum plants resulted in 50% reductions in Rca and AtpC messenger RNA levels. To investigate the role of these host proteins in TMV accumulation and plant defense, we used a Tobacco rattle virus vector to silence these genes in Nicotiana benthamiana plants prior to challenge with TMV expressing green fluorescent protein. TMV-induced fluorescent lesions on Rca- or AtpC-silenced leaves were, respectively, similar or twice the size of those on leaves expressing these genes. Silencing Rca and AtpC did not influence the spread of Tomato bushy stunt virus and Potato virus X. In AtpC- and Rca-silenced leaves TMV accumulation and pathogenicity were greatly enhanced, suggesting a role of both host-encoded proteins in a defense response against TMV. In addition, silencing these host genes altered the phenotype of the TMV infection foci and VRCs, yielding foci with concentric fluorescent rings and dramatically more but smaller VRCs. The concentric rings occurred through renewed virus accumulation internal to the infection front.
authors.affiliation: Plant Biology Division, The Samuel Roberts Noble Foundation, Inc., Ardmore, Oklahoma 73401, USA.
authors.forename: Sumana
authors.initials: S
authors.lastname: Bhat
authors.forename: Svetlana Y
authors.initials: SY
authors.lastname: Folimonova
authors.forename: Anthony B
authors.initials: AB
authors.lastname: Cole
authors.forename: Kimberly D
authors.initials: KD
authors.lastname: Ballard
authors.forename: Zhentian
authors.initials: Z
authors.lastname: Lei
authors.forename: Bonnie S
authors.initials: BS
authors.lastname: Watson
authors.forename: Lloyd W
authors.initials: LW
authors.lastname: Sumner
authors.forename: Richard S
authors.initials: RS
authors.lastname: Nelson
mesh_terms: D060365:Chloroplast Proteins / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism* / Q000821:virology; D020868:Gene Silencing; D005822:Genetic Vectors / Q000235:genetics / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D054884:Host-Pathogen Interactions; D010641:Phenotype; D010935:Plant Diseases / Q000821:virology; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D017863:Potexvirus / Q000378:metabolism / Q000472:pathogenicity; D025941:Protein Interaction Mapping; D021381:Protein Transport; D040901:Proteomics / Q000379:methods; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012324:RNA-Dependent RNA Polymerase / Q000235:genetics / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism / Q000821:virology*; D014027:Tobacco Mosaic Virus / Q000201:enzymology / Q000472:pathogenicity / Q000502:physiology*; D017864:Tombusvirus / Q000378:metabolism / Q000472:pathogenicity; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism; D014779:Virus Replication
chemical_list: D060365:Chloroplast Proteins; D010940:Plant Proteins; D012333:RNA, Messenger; D014764:Viral Proteins; C054765:rca protein, plant; D049452:Green Fluorescent Proteins; C085103:tobacco mosaic virus replicase; D012324:RNA-Dependent RNA Polymerase