title: Extensive 5.8S nrDNA polymorphism in Mammillaria (Cactaceae) with special reference to the identification of pseudogenic internal transcribed spacer regions.
abstract: The internal transcribed spacer (ITS) region (ITS1, 5.8S rDNA, ITS2) represents the most widely applied nuclear marker in eukaryotic phylogenetics. Although this region has been assumed to evolve in concert, the number of investigations revealing high degrees of intra-individual polymorphism connected with the presence of pseudogenes has risen. The 5.8S rDNA is the most important diagnostic marker for functionality of the ITS region. In Mammillaria, intra-individual 5.8S rDNA polymorphisms of up to 36% and up to nine different types have been found. Twenty-eight of 30 cloned genomic Mammillaria sequences were identified as putative pseudogenes. For the identification of pseudogenic ITS regions, in addition to formal tests based on substitution rates, we attempted to focus on functional features of the 5.8S rDNA (5.8S motif, secondary structure). The importance of functional data for the identification of pseudogenes is outlined and discussed. The identification of pseudogenes is essential, because they may cause erroneous phylogenies and taxonomic problems.
authors: Biozentrum, Martin Luther University of Halle-Wittenberg, Weinbergweg 22, 06120, Halle/Saale, Germany.
authors: Doerte
authors: D
authors: Harpke
authors: Angela
authors: A
authors: Peterson
mesh_terms: D001483:Base Sequence; D029421:Cactaceae / Q000235:genetics*; D017931:DNA Primers; D021901:DNA, Intergenic / Q000737:chemistry / Q000235:genetics*; D018744:DNA, Plant / Q000737:chemistry / Q000235:genetics*; D009690:Nucleic Acid Conformation; D016133:Polymerase Chain Reaction
chemical_list: D017931:DNA Primers; D021901:DNA, Intergenic; D018744:DNA, Plant