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

Abstract

This study analysed cytogenetic events occurring in the syncytial endosperm of the Avena magna H. C. Murphy & Terrell × Avena longiglumis Durieu amphiploid, which is a product of two wild species having different genomes. Selection through the elimination of chromosomes and their fragments, including those translocated, decreased the level of ploidy in the endosperm below the expected 3n, leading to the modal number close to 2n. During intergenomic translocations, fragments of the heterochromatin-rich C-genome were transferred to the D and Al genomes. Terminal and non-reciprocal exchanges dominated, whereas other types of translocations, including microexchanges, were less common. Using two probes and by counterstaining with DAPI, the A. longiglumis and the rare exchanges between the D and Al genomes were detected by GISH. The large discontinuity in the probe labelling in the C chromosomes demonstrated inequality in the distribution of repetitive sequences along the chromosome and probable intragenomic rearrangements. In the nucleus, the spatial arrangement of genomes was non-random and showed a sectorial-concentric pattern, which can vary during the cell cycle, especially in the less stable tissue like the hybrid endosperm.

Oat chromosome and genome evolution defined by widespread terminal intergenomic translocations in polyploids

“…Intergenomic translocations have not been identified in A. agadiriana using our selected probes, and the FISH pattern suggested that this species may be of autopolyploid origin thus its affiliation to the AABB group and potential drivers shaping this species remain debatable. Both our karyotype analysis and the data obtained by different authors (Jellen et al, 1994;Luo et al, 2018a, b;Tomaszewska and Kosina, 2021;Yan et al, 2021;Peng et al, 2022) indicated that some intergenomic translocations could also influence the divergence of the CCDD Avena group. Some translocations between the C and D genomes in hexaploid oat species involved the same chromosomes as in tetraploid CCDD species (this paper; Badaeva et al, 2010;Yan et al, 2021) supporting the hypothesis that one of the species belonging to this oat group contributed to the evolution of hexaploid Avena species.…”

“…A certain advantage of the repetitive DNA probes over the whole genomic DNA probes used for in situ hybridization is observed (Tomaszewska et al, 2022). Despite the often perfect discrimination of genomes in allopolyploids/amphiploids using total genomic DNA isolated from a diploid species (Tomaszewska and Kosina, 2021), such probes are not applicable to distinguish closely related genomes such as those observed in Brassica (Alix et al, 2008), Triticum (Tang et al, 2018), Cenchrus and Urochloa tropical forage grasses (Rathore et al, 2022;Tomaszewska et al, 2022) or highly homologous A and D genomes in Avena (Linares et al, 1998). The parental species of amphiploids studied here are meiotically compatible in the crossing process, exhibiting sometimes partial sterility (Loskutov, 2001), and these data together with established genome composition of hybrids and amphiploids contribute to a better understanding of the complex evolutionary processes within the genus Avena.…”

“…In new polyploids, many evolutionary processes occur above the organizational level of duplicated genes (Adams and Wendel, 2005). These include elimination of whole chromosomes or even whole genomes ( Hordeum : Gernand et al, 2005; Nicotiana: Patel et al, 2011) as well as intra- and inter-genomic chromosome translocations (Badaeva et al, 2007; Tomaszewska, 2021; Tomaszewska and Kosina, 2021). Changes occurring in polyploid nuclei may be associated with transposon activity (McClintock, 1984; Comai et al, 2003) and lead to the stabilization of polyploid genomes, thus increasing vitality and fertility, and extending the adaptive potential of such plants (Alix et al, 2017).…”

“…Diploid species are characterized by the presence of A or C genomes; the B genome is found only in some tetraploids. The D genome is present in all hexaploids (Badaeva et al, 2005) and some tetraploids (Yan et al, 2016, 2021; Tomaszewska and Kosina, 2021). The literature on the number and localization of intergenomic chromosome translocations in oats mainly uses in situ hybridization with total genomic DNA or some abundant repetitive DNA sequences (Chen and Armstrong, 1994; Jellen et al, 1994; Leggett et al, 1994; Linares et al, 2000; Tomaszewska and Kosina, 2021).…”

Variability in the quality of pollen grains in oat amphiploids and their parental species

“…The results showed no anomalous stamen formation in oat accessions. Therefore, the variability observed in the viability of pollen grains between the accessions of amphiploids and their parental species might be caused by disturbances in meiosis, resulting from the coexistence of several different genomes in the hybrid nuclei (Chen et al 1977;Tomaszewska and Kosina 2021). Meiotic anomalies can result in the formation of gametes with a reduced or increased number of chromosomes.…”