title: Recent population decline and selection shape diversity of taxol-related genes.
abstract: Taxanes are defensive metabolites produced by Taxus species (yews) and used in anticancer therapies. Despite their medical interest, patterns of natural diversity in taxane-related genes are unknown. We examined variation at five main genes of Taxus baccata in the Iberian Peninsula, a region where unique yew genetic resources are endangered. We looked at several gene features and applied complementary neutrality tests, including diversity/divergence tests, tests solely based on site frequency spectrum (SFS) and Zeng's compound tests. To account for specific demography, microsatellite data were used to infer historical changes in population size based on an Approximate Bayesian Computation (ABC) approach. Polymorphism-divergence tests pointed to positive selection for genes TBT and TAT and balancing selection for DBAT. In addition, neutrality tests based on SFS found that while a recent reduction in population size may explain most statistics' values, selection may still be in action in genes TBT and DBAT, at least in some populations. Molecular signatures on taxol genes suggest the action of frequent selective waves with different direction or intensity, possibly related to varying adaptive pressures produced by the host-enemy co-evolution on defence-related genes. Such natural selection processes may have produced taxane variants still undiscovered.
authors.affiliation: Department of Forest Ecology and Genetics, Center of Forest Research, INIA, Carretera de A Coruña km 7.5, E-28040 Madrid, Spain.
authors.forename: C
authors.initials: C
authors.lastname: Burgarella
authors.forename: M
authors.initials: M
authors.lastname: Navascués
authors.forename: M
authors.initials: M
authors.lastname: Zabal-Aguirre
authors.forename: E
authors.initials: E
authors.lastname: Berganzo
authors.forename: M
authors.initials: M
authors.lastname: Riba
authors.forename: M
authors.initials: M
authors.lastname: Mayol
authors.forename: G G
authors.initials: GG
authors.lastname: Vendramin
authors.forename: S C
authors.initials: SC
authors.lastname: González-Martínez
mesh_terms: D001483:Base Sequence; D019143:Evolution, Molecular; D005787:Gene Frequency; D017343:Genes, Plant; D014644:Genetic Variation; D005838:Genotype; D018895:Microsatellite Repeats; D008969:Molecular Sequence Data; D011110:Polymorphism, Genetic; D012641:Selection, Genetic; D017422:Sequence Analysis, DNA; D013030:Spain; D043823:Taxoids / Q000378:metabolism*; D020946:Taxus / Q000235:genetics* / Q000378:metabolism
chemical_list: D043823:Taxoids