title: Validation of high rates of nucleotide substitution in geminiviruses: phylogenetic evidence from East African cassava mosaic viruses.
abstract: Whitefly-transmitted geminiviruses are major pathogens of the important crop cassava in Africa. The intensive sampling and sequencing of cassava mosaic disease-causing viruses that occurred in the wake of a severe outbreak in Central Africa (1997-2002) allowed us to estimate the rate of evolution of this virus. East African cassava mosaic virus and related species are obligately bipartite (DNA-A and DNA-B segments), and these two genome segments have different evolutionary histories. Despite these phylogenetic differences, we inferred high rates of nucleotide substitution in both segments: mean rates of 1.60x10(-3) and 1.33x10(-4) substitutions site(-1) year(-1) for DNA-A and DNA-B, respectively. While similarly high substitution rates were found in datasets free of detectable recombination, only that estimated for the coat protein gene (AV1), for which an additional DNA-A sequence isolated in 1995 was available, was statistically robust. These high substitution rates also confirm that those previously estimated for the monopartite tomato yellow leaf curl virus (TYLCV) are representative of multiple begomoviruses. We also validated our rate estimates by comparing them with those depicting the emergence of TYLCV in North America. These results further support the notion that geminiviruses evolve as rapidly as many RNA viruses.
authors.affiliation: Department of Ecology, Evolution and Natural Resources, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, NJ 08901, USA.|Center for Infectious Disease Dynamics, Department of Biology, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Siobain
authors.initials: S
authors.lastname: Duffy
authors.affiliation: Fogarty International Center, National Institutes of Health, Bethesda, MD 20892, USA.|Center for Infectious Disease Dynamics, Department of Biology, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Edward C
authors.initials: EC
authors.lastname: Holmes
mesh_terms: D000351:Africa, Eastern; D053839:Begomovirus / Q000235:genetics* / Q000302:isolation & purification; D016000:Cluster Analysis; D004279:DNA, Viral / Q000235:genetics*; D002365:Manihot / Q000821:virology; D009029:Mosaic Viruses; D010802:Phylogeny; D017354:Point Mutation; D011110:Polymorphism, Genetic
chemical_list: D004279:DNA, Viral