title: Elevating fitness after a horizontal gene exchange in bacteriophage φX174.
abstract: In an earlier study, protein-based barriers to horizontal gene transfer were investigated by placing the bacteriophage G4 G gene, encoding the major spike protein, into the φX174 genome. The foreign G protein promoted off-pathway assembly reactions, resulting in a lethal phenotype. After three targeted genetic selections, one of two foreign spike proteins was productively integrated into the φX174 system: the complete G4 or a recombinant G4/φX174 protein (94% G4:6% φX174). However, strain fitness was very low. In this study, the chimeras were characterized and experimentally evolved. Inefficient assembly was the primary contributor to low fitness: accordingly, mutations affecting assembly restored fitness. The spike protein preference of the ancestral and evolved strains was determined in competition experiments between the foreign and φX174G proteins. Before adaptation, both G proteins were incorporated into virions; afterwards, the foreign proteins were strongly preferred. Thus, a previously inhibitory protein became the preferred substrate during assembly.
authors.affiliation: School of Plant Sciences and the BIO5 Institute University of Arizona, Tucson, AZ 85721, USA.
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Doore
authors.affiliation: School of Plant Sciences and the BIO5 Institute University of Arizona, Tucson, AZ 85721, USA.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Schweers
authors.affiliation: School of Plant Sciences and the BIO5 Institute University of Arizona, Tucson, AZ 85721, USA. Electronic address: bfane@email.arizona.edu.
authors.forename: Bentley A
authors.initials: BA
authors.lastname: Fane
mesh_terms: D010584:Bacteriophage phi X 174 / Q000235:genetics* / Q000502:physiology; D022761:Gene Transfer, Horizontal; D009154:Mutation; D014760:Viral Fusion Proteins / Q000235:genetics; D019065:Virus Assembly
chemical_list: D014760:Viral Fusion Proteins
keywords: Experimental evolution; Microviridae; Microvirus; Virus assembly; φX174