Functional and structural chromosome analyses in autotetraploid Silene latifolia
1999
Siroky, J. | Hodurkova, J. | Negrutiu, I. | Vyskot, B.
Recent immunocytological and molecular data show that heterochromatic nuclear regions, both constitutive and facultative, are modified differently (cytosine hypermethylation and histone hypoacetylation) and late replicating, when compared to euchromatin. Intrusive and/or additive (supernumerary) DNA sequences are often functionally silenced; this is accompanied by their heterochromatinization. In this work we present a number of karyological studies on autotetraploid female cells of Silene latifolia (syn. Melandrium album). Immunofluorescence analyses do not indicate any global differences in DNA methylation, histone H4 acetylation, and chromosome replication patterns which could arise as a consequence of the duplication of the whole chromosome set of the original diploid genome. Similarly, the number of silver-positive nucleoli roughly correlates to the ploidy level. Early replication and H4 hyperacetylation have been detected at all subterminal chromosome regions. This, together with cDNA in situ hybridization patterns, indicates the localization of gene-rich regions. DNA methylation and chromosome replication patterns, but not histone H4 acetylation, show differences among the four X chromosomes present: one to three X chromosomes were observed as hypermethylated and/or late replicating. Taken together, the data demonstrate that there is no overall silencing of the additional two sets of autosomes in the tetraploid cells, but the X chromosomes could be subject to an irregular dosage compensation.
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