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

Abstract

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.

Development of Wheat-Aegilops caudataIntrogression Lines and Their Characterisation Using Genome-Specific KASP Markers

“…In this study, we used the same set of addition lines for the assignment of the KASP markers to the C-genome chromosomes. Genotyping of these addition lines with the KASP markers showed that chromosome B (2C) had markers from wheat homoeologous groups 2/4 assigned to it (Table 1) which agreed with the work done by Danilova et al (2017). Chromosome G (4C) had KASP markers assigned from homoeologous groups 4/2/3/7.…”

“…caudata chromosome. An addition line for chromosome A is absent from this set, but reports have suggested it to be homoeologous to group 1 of wheat (Danilova et al, 2017; Friebe et al, 1992; Niu et al, 2018). Thus, the 26 markers that did not detect Ae.…”

“…The variation observed in the results indicates the presence of genomic rearrangements. Recently, studies by Danilova et al (2017), Gong et al (2017) and Niu et al (2018) on the Alcedo- Ae. caudata additions lines found that the C-genome chromosomes carried several inversions and translocations but did not agree on the rearrangements carried by each chromosome.…”

“…Alcedo)- Ae. caudata addition lines B-G (Schubert and Blüthner, 1992; Schubert and Blüthner, 1995) have also been characterised extensively in previous studies using cytogenetic markers (Friebe et al, 1992), isozyme analysis (Schmidt et al, 1993), Simple Sequence Repeat (SSR) markers (Gong et al, 2017; Niu et al, 2018; Peil et al, 1998), FISH with cDNA probes (Danilova et al, 2017), Conserved Orthologous Sequence (COS) and PCR-based Landmark Unique Gene (PLUG) markers (Gong et al, 2017), and sequential FISH and genomic in situ hybridization (GISH) (Niu et al, 2018). Many of these studies found that the Alcedo- Ae.…”

Chromosome Rearrangements Caused by Double Monosomy in Wheat-Barley Group-7 Substitution Lines

“…But colinear homoeologues do not pair during meiosis in hybrids of evolutionary diverse Triticeae, which conforms the existence of numerous allopolyploids [Tsunewaki, 2009;Feldman and Levy, 2012]. Thus, chromosome alterations, described in diploid grasses, known for homoploid hybrid origin and rearranged genomes, such as rye Secale cereale L. [Martis et al, 2013] and Aegilops markgrafii (Greuter) Hammer [Danilova et al, 2017], may arise through BFB cycles.…”