Major structural genomic alterations can be associated with hybrid speciation in Aegilops markgrafii (Triticeae)

• Published in: The Plant journal : for cell and molecular biology Vol. 92; no. 2; pp. 317 - 330
• Main Authors: Danilova, Tatiana V., Akhunova, Alina R., Akhunov, Eduard D., Friebe, Bernd, Gill, Bikram S.
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01.10.2017
• Subjects: Aegilops; Aegilops markgrafii; Allopolyploidy; Barley; Chromosome rearrangements; Chromosome translocations; Chromosomes; Chromosomes, Plant - genetics; Cytogenetics; Data processing; DNA Transposable Elements - genetics; Fluorescence; Fluorescence in situ hybridization; Gene Rearrangement; Gene sequencing; Genetic Speciation; Genome, Plant - genetics; Genomes; Goat grass; homoploid hybrid speciation; Hordeum - genetics; Hybridization; Hybridization, Genetic - genetics; In Situ Hybridization, Fluorescence; Interspecific; Interspecific hybridization; Inversions; Karyotype; karyotype evolution; Macrostructure; Nucleotide sequence; Phylogeny; Rye; Speciation; Triticeae; Triticum; Triticum - genetics; Wheat; karyotype evolution; homoploid hybrid speciation; Aegilops markgrafii; chromosome rearrangements; Triticeae
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/tpj.13657

Summary During evolutionary history many grasses from the tribe Triticeae have undergone interspecific hybridization, resulting in allopolyploidy; whereas homoploid hybrid speciation was found only in rye. Homoeologous chromosomes within the Triticeae preserved cross‐species macrocolinearity, except for a few species with rearranged genomes. Aegilops markgrafii, a diploid wild relative of wheat (2n = 2x = 14), has a highly asymmetrical karyotype that is indicative of chromosome rearrangements. Molecular cytogenetics and next‐generation sequencing were used to explore the genome organization. Fluorescence in situ hybridization with a set of wheat cDNAs allowed the macrostructure and cross‐genome homoeology of the Ae. markgrafii chromosomes to be established. Two chromosomes maintained colinearity, whereas the remaining were highly rearranged as a result of inversions and inter‐ and intrachromosomal translocations. We used sets of barley and wheat orthologous gene sequences to compare discrete parts of the Ae. markgrafii genome involved in the rearrangements. Analysis of sequence identity profiles and phylogenic relationships grouped chromosome blocks into two distinct clusters. Chromosome painting revealed the distribution of transposable elements and differentiated chromosome blocks into two groups consistent with the sequence analyses. These data suggest that introgressive hybridization accompanied by gross chromosome rearrangements might have had an impact on karyotype evolution and homoploid speciation in Ae. markgrafii. Significance Statement The chromosome macrostructure of the wild wheat relative Aegilops markgrafii was established. Molecular cytogenetic and comparative sequence analyses revealed that the rearranged chromosome blocks have a diverse phylogenetic affinity indicative of ancient homoploid interspecific hybridization.