title: Early function of the Abutilon mosaic virus AC2 gene as a replication brake.
abstract: The C2/AC2 genes of monopartite/bipartite geminiviruses of the genera Begomovirus and Curtovirus encode important pathogenicity factors with multiple functions described so far. A novel function of Abutilon mosaic virus (AbMV) AC2 as a replication brake is described, utilizing transgenic plants with dimeric inserts of DNA B or with a reporter construct to express green fluorescent protein (GFP). Their replicational release upon AbMV superinfection or the individual and combined expression of epitope-tagged AbMV AC1, AC2, and AC3 was studied. In addition, the effects were compared in the presence and in the absence of an unrelated tombusvirus suppressor of silencing (P19). The results show that AC2 suppresses replication reproducibly in all assays and that AC3 counteracts this effect. Examination of the topoisomer distribution of supercoiled DNA, which indicates changes in the viral minichromosome structure, did not support any influence of AC2 on transcriptional gene silencing and DNA methylation. The geminiviral AC2 protein has been detected here for the first time in plants. The experiments revealed an extremely low level of AC2, which was slightly increased if constructs with an intron and a hemagglutinin (HA) tag in addition to P19 expression were used. AbMV AC2 properties are discussed with reference to those of other geminiviruses with respect to charge, modification, and size in order to delimit possible reasons for the different behaviors.
  
  
  OBJECTIVE
  The (A)C2 genes encode a key pathogenicity factor of begomoviruses and curtoviruses in the plant virus family Geminiviridae. This factor has been implicated in the resistance breaking observed in agricultural cotton production. AC2 is a multifunctional protein involved in transcriptional control, gene silencing, and regulation of basal biosynthesis. Here, a new function of Abutilon mosaic virus AC2 in replication control is added as a feature of this protein in viral multiplication, providing a novel finding on geminiviral molecular biology.
authors.affiliation: Institut für Biomaterialien und Biomolekulare Systeme, Abteilung für Molekularbiologie und Virologie der Pflanzen, Universität Stuttgart, Stuttgart, Germany.
authors.forename: Björn
authors.initials: B
authors.lastname: Krenz
authors.affiliation: Institut für Biomaterialien und Biomolekulare Systeme, Abteilung für Molekularbiologie und Virologie der Pflanzen, Universität Stuttgart, Stuttgart, Germany.
authors.forename: Kathrin
authors.initials: K
authors.lastname: Deuschle
authors.affiliation: Institut für Biomaterialien und Biomolekulare Systeme, Abteilung für Molekularbiologie und Virologie der Pflanzen, Universität Stuttgart, Stuttgart, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Deigner
authors.affiliation: Institut für Biomaterialien und Biomolekulare Systeme, Abteilung für Molekularbiologie und Virologie der Pflanzen, Universität Stuttgart, Stuttgart, Germany.
authors.forename: Sigrid
authors.initials: S
authors.lastname: Unseld
authors.affiliation: Institut für Biomaterialien und Biomolekulare Systeme, Abteilung für Molekularbiologie und Virologie der Pflanzen, Universität Stuttgart, Stuttgart, Germany.
authors.forename: Gabi
authors.initials: G
authors.lastname: Kepp
authors.affiliation: Institut für Biomaterialien und Biomolekulare Systeme, Abteilung für Molekularbiologie und Virologie der Pflanzen, Universität Stuttgart, Stuttgart, Germany.
authors.forename: Christina
authors.initials: C
authors.lastname: Wege
authors.affiliation: Institut für Biomaterialien und Biomolekulare Systeme, Abteilung für Molekularbiologie und Virologie der Pflanzen, Universität Stuttgart, Stuttgart, Germany.
authors.forename: Tatjana
authors.initials: T
authors.lastname: Kleinow
authors.affiliation: Institut für Biomaterialien und Biomolekulare Systeme, Abteilung für Molekularbiologie und Virologie der Pflanzen, Universität Stuttgart, Stuttgart, Germany holger.jeske@bio.uni-stuttgart.de.
authors.forename: Holger
authors.initials: H
authors.lastname: Jeske
mesh_terms: D053839:Begomovirus / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015967:Gene Expression Regulation, Viral; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000032:analysis / Q000235:genetics; D030821:Plants, Genetically Modified / Q000821:virology; D014026:Nicotiana; D014764:Viral Proteins / Q000378:metabolism*; D014779:Virus Replication
chemical_list: C099182:AC2 protein, geminivirus; D004268:DNA-Binding Proteins; D014764:Viral Proteins; D049452:Green Fluorescent Proteins