title: Nucleotide distribution in gymnosperm nuclear sequences suggests a model for GC-content change in land-plant nuclear genomes.
abstract: Nuclear protein coding sequences from gymnosperms are currently scarce. We have determined 4 kb of nuclear protein coding sequences from gynosperms and have collected and analyzed > 60 kb of nuclear sequences from gymnosperms and nonspermatophytes in order to better understand processes influencing genome evolution in plants. We show that conifers possess both biased and nonbiased genes with respect to GC content, as found in monocots, suggesting that the common ancestor of conifers and monocots may have possessed both biased and nonbiased genes. The lack of biased genes in dicots is suggested to be a derived character for this lineage. We present a simple but speculative model of land-plant genome evolution which considers changes in GC bias and CpG frequency, respectively, as independent processes and which can account for several puzzling aspects of observed nucleotide frequencies in plant genes.
authors.affiliation: Institut für Genetik, Technische Universität Braunschweig, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Jansson
authors.forename: G
authors.initials: G
authors.lastname: Meyer-Gauen
authors.forename: R
authors.initials: R
authors.lastname: Cerff
authors.forename: W
authors.initials: W
authors.lastname: Martin
mesh_terms: D001482:Base Composition; D001483:Base Sequence; D005075:Biological Evolution; D003001:Cloning, Molecular; D003596:Cytosine; D017343:Genes, Plant; D016678:Genome; D006147:Guanine; D008969:Molecular Sequence Data; D010944:Plants / Q000235:genetics*; D013045:Species Specificity; D014197:Trees / Q000235:genetics
chemical_list: D006147:Guanine; D003596:Cytosine