期刊
MOLECULAR BIOLOGY AND EVOLUTION
卷 17, 期 6, 页码 942-950出版社
OXFORD UNIV PRESS
DOI: 10.1093/oxfordjournals.molbev.a026375
关键词
phi X174; beneficial mutations; microbial evolution; epistasis; inhibitor; adaptation
资金
- NIGMS NIH HHS [R01 GM057756, GM 57756] Funding Source: Medline
High temperature inhibits the growth of the wild-type bacteriophage phi X174. Three different point mutations were identified that each recovered growth at high temperature. Two affected the major capsid protein (residues F188 and F242), and one affected the internal scaffolding protein (B114). One of the major capsid mutations (F242) is located in a beta strand that contacts B114 in the procapsid during viral maturation, whereas the other capsid mutation (F188) is involved in subunit interactions at the threefold axis of symmetry. Selective coefficients of these mutations ranged from 13.9 to 3.8 in the inhibitory, hot environment, bur all mutations reduced fitness at normal temperature. The selective effect of one of the mutations (F242) was evaluated at high temperature in four different genetic backgrounds and exhibited epistasis of diminishing returns: as log fitness of the background genotype increased from -0.1 to 4.1, the fitness boost provided by the F242 mutation decreased from 3.9 to 0.8. These results support a model in which viral fitness is bounded by an upper limit and the benefit of a mutation is scaled according to the remaining opportunity for fitness improvement in the genome.
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