Chromosome and DNA methylation dynamics during meiosis in the autotetraploid Arabidopsis arenosa

Abstract

Variation in chromosome number due to polyploidy can seriously compromise meiotic stability. In autopolyploids, the presence of more than two homologous chromosomes may result in complex pairing patterns and subsequent anomalous chromosome segregation. In this context, chromocenter, centromeric, telomeric and ribosomal DNA locus topology and DNA methylation patterns were investigated in the natural autotetraploid, Arabidopsis arenosa. The data show that homologous chromosome recognition and association initiates at telomeric domains in premeiotic interphase, followed by quadrivalent pairing of ribosomal 45S RNA gene loci (known as NORs) at leptotene. On the other hand, centromeric regions at early leptotene show pairwise associations rather than associations in fours. These pairwise associations are maintained throughout prophase I, and therefore likely to be related to the diploid-like behavior of A. arenosa chromosomes at metaphase I, where only bivalents are observed. In anthers, both cells at somatic interphase as well as at premeiotic interphase show 5-methylcytosine (5-mC) dispersed throughout the nucleus, contrasting with a preferential co-localization with chromocenters observed in vegetative nuclei. These results show for the first time that nuclear distribution patterns of 5-mC are simultaneously reshuffled in meiocytes and anther somatic cells. During prophase I, 5-mC is detected in extended chromatin fibers and chromocenters but interestingly is excluded from the NORs what correlates with the pairing pattern.

Cork Oak Young and Traumatic Periderms Show PCD Typical Chromatin Patterns but Different Chromatin-Modifying Genes Expression

“…The antibodies used were chosen since they have been extensively tested in several studies in both plants and animals (Bianco-Miotto et al, 2010; Carvalho et al, 2010; She and Baroux, 2015; Groth et al, 2016) and their specificity has been verified (Nettersheim et al, 2013). Briefly, cell walls were partially digested with 2% cellulose (Sigma-Aldrich, Spain) in 1x PBS and hydrolysable tannins digested with 2 U/ml of tannase (Thermo Fisher Scientific, Waltham, MA, United States).…”

Genetic Adaptation Associated with Genome-Doubling in Autotetraploid Arabidopsis arenosa

“…Like A. lyrata , A. arenosa is obligately outcrossing, and abundant throughout Europe [16], [17]. Tetraploid A. arenosa is cytologically diploidized, with primarily bivalent chromosome associations at meiosis [18]. We sequenced the genomes of twelve tetraploid A. arenosa individuals from four populations in Germany and Austria and tested for allele frequency patterns suggestive of selective sweeps.…”

Genetic mapping in polyploids

“…In this thesis we have provided clear evidence for the existence of quadrivalents in the meiosis of autopolyploids like potato and rose (Chapter 3 and Chapter 5, respectively). Therefore, the assertion that quadrivalents are aberrant structures that cause a failure in the proper division of homologues (Darlington, 1937;Kostoff, 1940;Carvalho et al, 2010;Lloyd and Bomblies, 2016) does not hold across all species (and particularly not among established autopolyploids, many of which are domesticated crop species). Here we are once more plagued by the survivors' paradox: it could be that the 20 -30% quadrivalent pairings that we estimated to have contributed to the potato AxC population (Chapters 3, 8) might only represent a fraction of the multivalent meioses that occurred, the rest having perished.…”