Ribosomal DNA, tri- and bi-partite pericentromeres in the permanent translocation heterozygote Rhoeo spathacea

Abstract

High-and low-stringency FISH and base-specific fluorescence were performed on the permanent translocation heterozygote Rhoeo spathacea (2n = 12).Our results indicate that 45S rDNA arrays, rDNA-related sequences and other GC-rich DNA fraction(s) are located within the pericentromeric regions of all twelve chromosomes, usually colocalizing with the chromomycin A 3 -positive bands. Homogenization of the pericentromeric regions appears to result from the concerted spread of GC-rich sequences, with differential amplification likely. We found new 5S rDNA patterns, which suggest a variability in the breakpoints and in the consequent chromosome reorganizations. It was found that the large 5S rDNA locus residing on each of the 8E and 9E arms consisted of two smaller loci. On each of the two chromosome arms 3b and 4b, in addition to the major subtelomeric 5S rDNA locus, a new minor locus was found interstitially about 40% along the arm length. The arrangement of cytotogenetic landmarks and chromosome arm measurements are discussed with regard to genome repatterning in Rhoeo.

Variable multivalent orientations during diakinesis and metaphase I in microsporocytes ofTradescantia spathaceaSw.

“…Since in translocation heterozygotes such as Tradescantia a ring configuration is formed when each individual chromosome exchanges segments with two other non homologous chromosomes, their absence could be the result of failure of chiasmata in some segments of the interchange complex. As in Tradescantia spathacea all the 12 chromosomes involved in interchanges have been identified and ordered according to their relative position within the meiotic super structure, and designated as Aa-aB-Bb-bC-Cc-cD-Dd-dE-Ee-eF-Ff-fA (Sax 1931;Lin and Paddock 1973;Golczyk et al 2005Golczyk et al , 2010Golczyk 2011aGolczyk , 2011b), a ring structure would be expected if the two chromosomes flanking the chain, i.e. Aa and fA, pair with each other.…”

“…Such structures are the result of interchanges between all the 12 chromosomes of the complement with each chromosome sharing partial homology with two others without altering the chromosome number. Owing to its atypical chromosome behavior this plant has been studied extensively for karyotype (Darlington 1929(Darlington , 1938Kato 1930;Sax 1931;Sax and Anderson 1933;Coleman 1941;Lin and Paddock 1973;Golcyzk et al 2005), C-banding (Natrajan and Natrajan 1972;Pettanati 1987;Pattankar andRanjekar 1988, Golcyzk andJoachimiak 1999), arrangement of AT-GC rich chromatin, NORs, 5s and 45s rDNA (Golczyk and Joachimiak 2003, 2008, Golczyk et al 2010Golczyk 2011aGolczyk , 2011b) and the meiotic behavior of chromosomes (Belling 1927;Kato 1930;Koller 1932;Akemine 1937;Bhaduri 1942;Simmonds 1945;Walters and Gerstel 1948;Desai 1965;Wimber 1968;Moens 1972;Satterfield and Mertens 1972;Mertens 1973;Lin 1979aLin , 1979bLin , 1980Lin , 1982aLin , 1982bLin and Paddock 1973;Lin and Lee 1979;Verma and Ohri 1979;Jahan and Vahidy 1994;K...…”

Translocations of Chromosome End-Segments and Facultative Heterochromatin Promote Meiotic Ring Formation in Evening Primroses

“…Chromosome preparations were treated as described earlier (Golczyk et al, 2010). To detect the 45S DNA sites, the 25S rDNA region of the 45S rRNA-encoding unit of Arabidopsis thaliana (Unfried and Gruendler, 1990) labeled with digoxigenin-11-dUTP (Roche Applied Science) or tetramethyl-rhodamine-5-dUTP (Roche Applied Science) by nick-translation (Nick translation kit; Roche Applied Science) was used as a probe.…”

“…The deoxyribonucleotide oligomers (59-CCCTAAA-39) 4 and (59-CCCTAA-39) 4 synthesized with Cy3 at either end (Isogen Life Science) were used to search for Arabidopsis-type and vertebrate-type telomeric DNA motifs, respectively. The FISH protocol, including stringency washes and signal detection, was already described (Golczyk et al, 2010).…”

Intraspecific polymorphism of ribosomal DNA loci number and morphology in Brachypodium pinnatum and Brachypodium sylvaticum

“…rDNA sequences are also useful chromosome landmarks and provide important information about genome evolution at the chromosomal level. In some species, such as Arabidopsis thaliana [7], Hordeum vulgare [8] and Rhoeo spathacea [9,10], fluorescence in situ hybridisation (FISH) with 25S and 5S rDNA as probes is sufficient to identify each chromosome in the complement. A complementary approach that can be used for karyotype characterization is double fluorescent banding with DAPI and CMA fluorochromes, which discriminates between ATand GC-rich DNA regions.…”