[Chromosomal structure of the hybrids between Allium cepa L. and Allium fistulosum L. with relative resistance to downy mildew based on in situ hybridization].

Genomic in situ hybridization (GISH) was used for a chromosomal composition study of the later generations of interspecific hybrids between A. cepa L. and A. fistulosum L., which are relatively resistant to downy mildew (peronosporosis). GISH revealed that F2 hybrids, which did not produce seeds, were triploids (2n = 3x = 24) with 24 chromosomes and possessed in their compliments 16 chromosomes of A. fistulosum L. and eight chromosomes of A. cepa L. or eight chromosomes of A. fistulosum L. and 16 chromosomes of A. cepa L. The advanced F5 hybrid, which produced few seeds, was amphidiploid with 32 chromosomes. BC1F5 hybrid was triploid with eight chromosomes of A. fistulosum L. and 16 chromosomes of A. cepa L., which did not produce seeds. BC2 (BC1F5) plant was amphidiploid that possessed 4 recombinant chromosomes and produced few seeds. GISH results point to 2n-gametes formation in macro- and microsporogenesis of the hybrids. The mechanism of 2n-gametes formation and the possibility of apomixes events in the backcrossing progeny are discussed.

[Chromosomal organization of centromeric Ty3/gypsy retrotransposons in Allium cepa L. and Allium fistulosum L].

This is the first report on the presence of Ty3/gypsy-like retrotransposons in the centromeric region of Allium cepa and Allium fistulosum. The paper identifies the putative Ty3/gypsy centromeric retrotransposons (CR) among the DNA sequences of A. cepa present in the NCBI database and evaluates their copy number in the genomes of Allium cepa and Allium fistulosum. The putative copy number of Ty3/gypsy CR constituted about 26000 for A. cepa and about 7000 for A. fistulosum. The chromosomal organization of Ty3/gypsy CR was analyzed with the help of fluorescent in situ hybridization (FISH). The 300-bp PCR products synthesized with genomic DNA of Allium cepa and Allium fistulosum and primers designed for the sequence ET645811 of A. cepa (Genome Survey Sequence database), displaying similarity to the reverse transcriptase of the CR Ty3/gypsy family, served as FISH hybridization probes. On the chromosomes of A. cepa, hybridization signals were mainly localized in the centromeric region. On the chromosomes of A. fistulosum the signals were less expressed in the centromeric regions, though they were abundant in other chromosomal regions. The pathways of evolution in these closely related species are discussed.

[Chromosome organization of Ty1-copia-like retrotransposons in the tomato genome].

Ty1-copia-like retrotransposons were discovered in all studied plants and form a considerable fraction of their genomes. PCR amplification of a pool of fragments of the reverse transcriptase gene of Ty1-copia-like retrotransposons of the tomato genome was conducted and their physical organization in mitotic and meiotic chromosomes was studied. The method of fluorescence in situ hybridization revealed the location of retrotransposons in the pericentromeric heterochromatin and their absence in the nucleolus organizer region. Knowledge of physical distribution of retrotransposons in the tomato genome is important when constructing molecular markers on their basis. Comparative analysis of chromosomal location of retrotransposons in different plant species extends our knowledge of the plant genome evolution.

The integration of recombination and physical maps in a large-genome monocot using haploid genome analysis in a trihybrid allium population.

Integrated mapping in large-genome monocots has been carried out on a limited number of species. Furthermore, integrated maps are difficult to construct for these species due to, among other reasons, the specific plant populations needed. To fill these gaps, Alliums were chosen as target species and a new strategy for constructing suitable populations was developed. This strategy involves the use of trihybrid genotypes in which only one homeolog of a chromosome pair is recombinant due to interspecific recombination. We used genotypes from a trihybrid Allium cepa x (A. roylei x A. fistulosum) population. Recombinant chromosomes 5 and 8 from the interspecific parent were analyzed using genomic in situ hybridization visualization of recombination points and the physical positions of recombination were integrated into AFLP linkage maps of both chromosomes. The integrated maps showed that in Alliums recombination predominantly occurs in the proximal half of chromosome arms and that 57.9% of PstI/MseI markers are located in close proximity to the centromeric region, suggesting the presence of genes in this region. These findings are different from data obtained on cereals, where recombination rate and gene density tends to be higher in distal regions.

[Organization of the 378 bp satellite repeat in terminal heterochromatin of Allium fistulosum]. / Izuchenie organizatsii satellitnogo povtora 378 pn v terminal'nom geterokhromatine Allium fistulosum.

Telomeres, DNA-protein structures, are important elements of the eukaryotic chromosome. Telomeric regions of the majority of higher plants contain heptanucleotides TTTAGGG arranged into a tandem repeat. However, some taxa have no such repeats. These are some species of lilies (Lilium) and onions (Allium). For example, terminal regions of chromosomes of Spanish onion (Allium fistulosum) contain satellite DNA whose unit repeats are 380 bp in length, and the short arm of its chromosome 8 contains rDNA repeats. This study deals with the terminal heterochromatin and organization of the satellite repeat in A. fistulosum. Fluorescent in situ hybridization (FISH) was used to locate the satellite DNA on chromosomes and on extended DNA of A. fistulosum. Nonsatellite DNA was found in the structure of telomeric repeat. Polymerase chain reaction (PCR) and Southern hybridization were used for analysis of terminal heterochromatin. Various rearrangements were found in the satellite repeat. The roles of retrotransposones and microsatellites in the formation of terminal heterochromatin are discussed.

Localization of single-copy T-DNA insertion in transgenic shallots (Allium cepa) by using ultra-sensitive FISH with tyramide signal amplification.

The sensitivity of fluorescence in situ hybridization (FISH) for mapping plant chromosomes of single-copy DNA sequences is limited. We have adapted for plant cytogenetics a new signal-amplification method termed tyramide-FISH (Tyr-FISH). Until present this technique has only been applied to human chromosomes. The method is based on enzymatic deposition of fluorochrome-conjugated tyramide. With Tyr-FISH it was possible to detect target T-DNA sequences on plant metaphase chromosomes as small as 710 bp without using a cooled CCD camera. Short detection time and high sensitivity, in combination with a low background, make the Tyr-FISH method very suitable for routine application in plant cytogenetic research. With Tyr-FISH we analysed the position of T-DNA inserts in transgenic shallots. We found that the inserts were preferentially located in the distal region of metaphase chromosomes. Sequential fluorescence in situ hybridization with a 375 bp satellite sequence suggested that a specific T-DNA insert was located within the satellite sequence hybridization region on a metaphase chromosome. Analysis of less-condensed prophase and interphase chromosomes revealed that the T-DNA was integrated outside the satellite DNA-hybridization region in a more proximal euchromatin region.

[Manifestation of the mutagenic effect of acemidophen depending on its metabolism in various mammalian species (acemidophen--a promutagen)]. / Proiavlenie mutagennogo éffekta atsemidofena v zavisimosti ot ego metabolizma u raznykh vidov mlekopitaiushchikh (atsemidofen--promutagen).

While studying the specific variability of metabolism of the fasciolacide anthelmintic acemidophen, it is found that it possesses no mutagenic activity. This activity is peculiar to its metabolite-free amine L2, formed in mice organism by deacetylation. Thus, acemidophen is shown to be promutagen.