Interstitial telomere-like repeats in the monocot family Araceae

Abstract

Combining molecular cytogenetics and phylogenetic modelling of chromosome number change can shed light on the types of evolutionary changes that may explain the haploid numbers observed today. Applied to the monocot family Araceae, with chromosome numbers of 2n = 8 to 2n = 160, this type of approach has suggested that descending dysploidy has played a larger role than polyploidy in the evolution of the current chromosome numbers. To test this, we carried out molecular cytogenetic analyses in 14 species from 11 genera, using probes for telomere repeats, 5S rDNA and 45S rDNA and a plastid phylogenetic tree covering the 118 genera of the family, many with multiple species. We obtained new chromosome counts for six species, modelled chromosome number evolution using all available counts for the family and carried out fluorescence in situ hybridization with three probes (5S rDNA, 45S rDNA and Arabidopsis‐like telomeres) on 14 species with 2n = 14 to 2n = 60. The ancestral state reconstruction provides support for a large role of descending dysploidy in Araceae, and interstitial telomere repeats (ITRs) were detected in Anthurium leuconerum, A. wendlingeri and Spathyphyllum tenerum, all with 2n = 30. The number of ITR signals in Anthurium (up to 12) is the highest so far reported in angiosperms, and the large repeats located in the pericentromeric regions of A. wendlingeri are of a type previously reported only from the gymnosperms Cycas and Pinus. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 177, 15–26.

Towards a FISH-based karyotype of Rosa L. (Rosaceae)

“…This result suggest that these chromosomes (1, 2 and 7) may contain truncated or diverged telomere motifs. As a consequence for our experiments, the telomeric probe may be much more informative as cytogenetic marker when hybridized at a lower temperature than at 37°C (Fuchs et al 1995, Tek and Jiang 2004, Sousa et al 2014, Sousa and Renner 2015). However, the application of ITR markers under the low-hybridization stringency and simultaneous mapping of other probes (e.g.…”

“…The position of ITR on chromosomes can also reflect ancient chromosomal rearrangement as telomeric sequences and their remnants are involved in chromosomal rearrangements via illegitimate recombination between centromeric/telomeric repeats (Murat et al 2010) and can be associated with fragile sites of chromosomes (Grabowska-Joachimiak et al 2015). In addition, the chromosomal location of ITR can be used to detect descending dysploidy (Sousa and Renner 2015). …”

Diploid chromosome-scale assembly of theMuscadinia rotundifoliagenome supports chromosome fusion and disease resistance gene expansion duringVitisandMuscadiniadivergence

“…The marker-containing regions used for Trayshed chromosome structure validation also support 312 this hypothesis; all markers aligning Trayshed LG 7 and 20 were associated with V. vinifera 313 chromosome 7 ( Figure 1B). Telomere repeats can be used as indicators of chromosome number 314 reduction rearrangements (Sousa and Renner 2015). An enrichment of these sequences is expected 315 in a genomic region if a fusion occurred.…”

Chromosome number reduction in the sister clade of Carica papaya with concomitant genome size doubling

“…We here used a molecular‐clock‐dated phylogeny for all species of Caricaceae to infer the direction and timing of changes in chromosome number (with our new data now available for 50% of the species) and FISH to test for the presence of interstitial telomere repeats (ITRs) in species with reduced chromosome numbers, as a possible indication of recent chromosomal fusions. Interstitial telomere repeats have been used as footprints of (evolutionarily recent) chromosome fusion in angiosperms and gymnosperms, such as in the legume Vicia faba , the Malvaceae Sideritis montana , in Solanum , in species of the Araceae genus Typhonium , and in Picea and Pinus (Presting et al, 1996; Schmidt et al, 2000; He et al, 2013; Sousa et al, 2014; Sousa and Renner, 2015). We also tested the expectation that genome sizes in Caricaceae would stay within a narrow range (as in Brassicaceae; Lysak et al, 2009), given the absence of polyploidy in the family and the apparent stability of chromosomal homology across some of their genera (Iovene et al, 2015).…”