Journal Article

Bidirectional interlocus concerted evolution following allopolyploid speciation in cotton (Gossypium)

Seelanan, T, Schnabel, A, Wendel, J.F. (Iowa State University, Ames, IA.)

1995

Overview

Polyploidy is a prominent process in plant evolution; yet few data address the question of whether homeologous sequences evolve independently subsequent to polyploidization. We report on ribosomal DNA (rDNA) evolution in five allopolyploid (AD genome) species of cotton (Gossypium) and species representing their diploid progenitors (A genome, D genome). Sequence data from the internal transcribed spacer regions (ITS1 and ITS2) and the 5.8S gene indicate that rDNA arrays are homogeneous, or nearly so, in all diploids and allopolyploids examined. Because these arrays occur at four chromosomal loci in allopolyploid cotton, two in each subgenome, repeats from different arrays must have become homogenized by interlocus concerted evolution. Southern hybridization analysis combined with copy-number estimation demonstrate that this process has gone to completion in the diploids and to completion or near-completion in all allopolyploid species and that it most likely involves the entire rDNA repeat. Phylogenetic analysis demonstrates that interlocus concerted evolution has been bidirectional in allopolyploid species--i.e., rDNA from four polyploid lineages has been homogenized to a D genome repeat type, whereas sequences from Gossypium mustelinum have concerted to an A genome repeat type. Although little is known regarding the functional significance of interlocus concerted evolution of homeologous sequences, this study demonstrates that the process occurs for tandemly repeated sequences in diploid and polyploid plants. That interlocus concerted evolution can occur bidirectionally subsequent to hybridization and polyploidization has significant implications for phylogeny reconstruction, especially when based on rDNA sequences

• Publisher: National Academy of Sciences of the United States of America,National Acad Sciences
• Subject: ADN / Allopolyploidy / ARN RIBOSOMAL / ARN RIBOSOMIAL / Base Sequence / Biological Evolution / chemotaxonomy / CHIMIOTAXONOMIE / classification / Concerted evolution / Diploidy / DNA Primers / DNA, Plant / DNA, Plant - genetics / DNA, Ribosomal / DNA, Ribosomal - genetics / EVOLUCION / EVOLUTION / FILOGENIA / GENE / GENES / genetics / GENOMAS / GENOME / Genome, Plant / Genomes / Geography / GOSSYPIUM / Gossypium - classification / Gossypium - genetics / GOSSYPIUM ARBOREUM / GOSSYPIUM HERBACEUM / GOSSYPIUM HIRSUTUM / GOSSYPIUM RAIMONDII / GOSSYPIUM TOMENTOSUM / Homogenization / internal transcribed spacers / Molecular Sequence Data / Phylogenetics / PHYLOGENIE / Phylogeny / Plants / POLIPLOIDIA / Polymerase Chain Reaction / POLYPLOIDIE / Polyploidy / QUIMIOTAXONOMIA / Restriction Mapping / Ribosomal DNA / ribosomal RNA / RIBOSOMAS / RIBOSOME / SECUENCIA NUCLEICA / SEQUENCE NUCLEIQUE / Southern blotting / structural genes / TECHNIQUE ANALYTIQUE / TECNICAS ANALITICAS