13 research outputs found
Tracing the Evolution of the Angiosperm Genome from the Cytogenetic Point of View
Cytogenetics constitutes a branch of genetics that is focused on the cellular components,
especially chromosomes, in relation to heredity and genome structure, function and evolution.
The use of modern cytogenetic approaches and the latest microscopes with image acquisition and
processing systems enables the simultaneous two- or three-dimensional, multicolour visualisation of
both single-copy and highly-repetitive sequences in the plant genome. The data that is gathered using
the cytogenetic methods in the phylogenetic background enable tracing the evolution of the plant
genome that involve changes in: (i) genome sizes; (ii) chromosome numbers and morphology; (iii) the
content of repetitive sequences and (iv) ploidy level. Modern cytogenetic approaches such as FISH
using chromosome- and genome-specific probes have been widely used in studies of the evolution
of diploids and the consequences of polyploidy. Nowadays, modern cytogenetics complements
analyses in other fields of cell biology and constitutes the linkage between genetics, molecular biology
and genomics
Corrigendum: To Be or Not to Be Expressed: The First Evidence of a Nucleolar Dominance Tissue-Specificity in Brachypodium hybridum
This corrects the article "To Be or Not to Be Expressed: The First Evidence of a Nucleolar Dominance Tissue-Specificity in Brachypodium hybridum" in volume 12, 768347
To Be or Not to Be Expressed: The First Evidence of a Nucleolar Dominance Tissue-Specificity in Brachypodium hybridum
Nucleolar dominance (ND) is an epigenetic, developmentally regulated phenomenon
that describes the selective inactivation of 35S rDNA loci derived from one progenitor
of a hybrid or allopolyploid. The presence of ND was documented in an allotetraploid
grass, Brachypodium hybridum (genome composition DDSS), which is a polyphyletic
species that arose from crosses between two putative ancestors that resembled the
modern B. distachyon (DD) and B. stacei (SS). In this work, we investigated the
developmental stability of ND in B. hybridum genotype 3-7-2 and compared it with
the reference genotype ABR113. We addressed the question of whether the ND is
established in generative tissues such as pollen mother cells (PMC). We examined
condensation of rDNA chromatin by fluorescence in situ hybridization employing stateof-
art confocal microscopy. The transcription of rDNA homeologs was determined by
reverse-transcription cleaved amplified polymorphic sequence analysis. In ABR113, the
ND was stable in all tissues analyzed (primary and adventitious root, leaf, and spikes).
In contrast, the 3-7-2 individuals showed a strong upregulation of the S-genome units
in adventitious roots but not in other tissues. Microscopic analysis of the 3-7-2 PMCs
revealed extensive decondensation of the D-genome loci and their association with the
nucleolus in meiosis. As opposed, the S-genome loci were always highly condensed and
localized outside the nucleolus. These results indicate that genotype-specific loss of ND
in B. hybridum occurs probably after fertilization during developmental processes. This
finding supports our view that B. hybridum is an attractive model to study ND in grasses
Cytomolecular Organisation of the Nuclear Genome
Modern molecular cytogenetics allows many aspects of the nuclear genome structure, function, and evolution to be analysed within the topographic context of mitotic and meiotic chromosomes and interphase nuclei [...
The fate of 35S rRNA genes in the allotetraploid grass Brachypodium hybridum
Nucleolar dominance (ND) consists of the reversible silencing of 35S/45S rDNA loci inherited from one of the ancestors of an allopolyploid. The molecular mechanisms by which one ancestral rDNA set is selected for silencing remain unclear. We applied a combination of molecular (Southern blot hybridization and reverse-transcription cleaved amplified polymorphic sequence analysis), genomic (analysis of variants) and cytogenetic (fluorescence in situ hybridization) approaches to study the structure, expression and epigenetic landscape of 35S rDNA in an allotetraploid grass that exhibits ND, Brachypodium hybridum (genome composition DDSS), and its putative progenitors, Brachypodium distachyon (DD) and Brachypodium stacei (SS). In progenitor genomes, B. stacei showed a higher intragenomic heterogeneity of rDNA compared with B. distachyon. In all studied accessions of B. hybridum, there was a reduction in the copy number of S homoeologues, which was accompanied by their inactive transcriptional status. The involvement of DNA methylation in CG and CHG contexts in the silencing of the S-genome rDNA loci was revealed. In the B. hybridum allotetraploid, ND is stabilized towards the D-genome units, irrespective of the polyphyletic origin of the species, and does not seem to be influenced by homoeologous 35S rDNA ratios and developmental stage