title: Limitations on geminivirus genome size imposed by plasmodesmata and virus-encoded movement protein: insights into DNA trafficking.
abstract: Animals and plants evolved systems to permit non-cell-autonomous trafficking of RNA, whereas DNA plays a cell-autonomous role. In plants, plasmodesmata serve as the conduit for this phenomenon, and viruses have evolved to use this pathway for the spread of infectious nucleic acids. In this study, a plant DNA virus was used to explore the constraints imposed on the movement of DNA through this endogenous RNA trafficking pathway. The combined properties of the geminivirus-encoded movement protein and plasmodesmata were shown to impose a strict limitation on the size of the viral genome at the level of cell-to-cell movement. Size-increased viral genome components underwent homologous and nonhomologous recombination to overcome this strict limitation. Our results provide insights into the genetic mechanisms that underlie viral evolution and provide a likely explanation for why relatively few types of plant DNA viruses have evolved: they would have had to overcome the constraints imposed by an endogenous system operating to ensure that DNA acts in a cell-autonomous manner.
authors.affiliation: Department of Plant Pathology, College of Agriculture and Enviromental Sciences, University of California, Davis, California 95616, USA.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Gilbertson
authors.forename: Mysore
authors.initials: M
authors.lastname: Sudarshana
authors.forename: Hao
authors.initials: H
authors.lastname: Jiang
authors.forename: Maria R
authors.initials: MR
authors.lastname: Rojas
authors.forename: William J
authors.initials: WJ
authors.lastname: Lucas
mesh_terms: D003001:Cloning, Molecular; D004279:DNA, Viral / Q000737:chemistry / Q000235:genetics; D019143:Evolution, Molecular; D017791:Geminiviridae / Q000235:genetics* / Q000502:physiology; D016679:Genome, Viral; D009154:Mutation; D010944:Plants / Q000821:virology*; D010957:Plasmids / Q000235:genetics; D031425:Plasmodesmata / Q000502:physiology / Q000821:virology*; D021381:Protein Transport; D020733:RNA, Small Cytoplasmic / Q000235:genetics / Q000502:physiology; D014764:Viral Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: C117734:BC1 RNA; D004279:DNA, Viral; D020733:RNA, Small Cytoplasmic; D014764:Viral Proteins