New evidence confirming the CD genomic constitutions of the tetraploid Avena species in the section Pachycarpa Baum

Abstract

The tetraploid Avena species in the section Pachycarpa Baum, including A. insularis, A. maroccana, and A. murphyi, are thought to be involved in the evolution of hexaploid oats; however, their genome designations are still being debated. Repetitive DNA sequences play an important role in genome structuring and evolution, so understanding the chromosomal organization and distribution of these sequences in Avena species could provide valuable information concerning genome evolution in this genus. In this study, the chromosomal organizations and distributions of six repetitive DNA sequences (including three SSR motifs (TTC, AAC, CAG), one 5S rRNA gene fragment, and two oat A and C genome specific repeats) were investigated using non-denaturing fluorescence in situ hybridization (ND-FISH) in the three tetraploid species mentioned above and in two hexaploid oat species. Preferential distribution of the SSRs in centromeric regions was seen in the A and D genomes, whereas few signals were detected in the C genomes. Some intergenomic translocations were observed in the tetraploids; such translocations were also detected between the C and D genomes in the hexaploids. These results provide robust evidence for the presence of the D genome in all three tetraploids, strongly suggesting that the genomic constitution of these species is DC and not AC, as had been thought previously.

Cytogenetic events in the endosperm of amphiploid Avena magna × A. longiglumis

“…The present molecular studies on oat genomes proved that the A genomes of A. maroccana, A. magna, and A. muphyi have to be considered as D genome (Yan et al 2016 ; Yan et al 2021 ; Paulina Tomaszewska, pers. comm.).…”

“…The author analysed cp and mt genomes and proved that A. longiglumis was a maternal component that created Avena insularis Ladiz. (AACC genomes; currently CCDD, Yan et al 2021 ), and subsequently a paternal species with A. insularis as a maternal species in the evolution of the AACCDD species. A. insularis and A. magna were recognised as closely related taxa (Shelukhina et al 2007 ; Yan et al 2021 ).…”

“…(AACC genomes; currently CCDD, Yan et al 2021 ), and subsequently a paternal species with A. insularis as a maternal species in the evolution of the AACCDD species. A. insularis and A. magna were recognised as closely related taxa (Shelukhina et al 2007 ; Yan et al 2021 ). Thus, in the light of the above data, the research of a ‘magna-longiglumis’ hybrid unit and its endosperm can significantly supplement the knowledge about the biology of the cereal developing large caryopses.…”

Reference genome assemblies reveal the origin and evolution of allohexaploid oat

“…Major interchromosomal exchanges between the C and D subgenomes of A. insularis and SFS were detected by using FISH technology with the C genome-specific repeat Am1 as the probe. Metaphase chromosome preparation 66 and FISH analysis 67 were performed as previously described (Fig. 4d, Extended Data Fig.…”

A universal karyotypic system for hexaploid and diploid Avena species brings oat cytogenetics into the genomics era

“…The non-denaturing fluorescence in situ hybridization (ND-FISH), using oligonucleotide (oligo) probes of repetitive sequences, has been confirmed as a simple, cheap and high-throughput method for painting the chromosomes of different plant species [ 23 – 26 ]. The FISH signal patterns of some probes, including simple sequence repeat (SSR) motifs, have previously been documented for several different oat lines [ 20 , 27 – 31 ]. However, the FISH patterns of those SSRs are highly polymorphic, which may cause difficulties for the assignment of specific chromosomes to certain sub-genomes and linkage groups.…”