Multiple reconstruction of barley karyotype resulting in complete cytological marking of the chromosome complement

Abstract

A new reconstructed barley karyotype, PK88, which is a quadruple homozygote for three unequal translocations, 1-2, 3-4, 5-7, and one pericentric inversion in chromosome 6, was studied. As a result of these chromosome rearrangements, a complete cytological marking of the complement has been achieved. Due to the specific intra or interchromosomal transfer of particular bands, Giemsa staining of somatic chromosomes provided clear-cut indications about the localization of translocation and inversion breakpoints. It was established that the long arms of chromosomes 1, 2, 4, 5 and 7 and the short arm of chromosome 3 have been involved in interchanges 1-2, 3-4, and 5-7. The breakpoints of pericentric inversion proved to be located proximally to the short (satellite) arm and distally in the long arm of chromosome 6. PK-88 offers an essential gain in resolution power and extension of the areas of application in cytogenetics over other reconstructed karyotypes produced so far in barley.

Molecular Cytogenetic Characterization of a New Reconstructed Barley Karyotype

“…this approach was successfully applied to map the heterochromatic segments in barley karyotype, since the pericentromeric regions of nearly all chromosomes of this species were found to carry heavy n-bands making it impossible to localize precisely the position of the centromeres directly in Giemsa N-banded plates. As expected, the data concerning the distribution pattern of n-bands along the individual chromosomes, obtained in this study, completely confirmed our results from previous analogous investigations with the parental lines of PK 88-19 (6,8). What is interesting to see on this figure, however, is that the identity of each chromosome of the complement is readily apparent in a routinely stained preparation, thus having no need to use laborious, sophisticated techniques in barley cytogenetic studies.…”

“…FISH analysis of the reconstructed chromosomes resulting from this interchange allowed to attain significantly higher precision in the location of the translocation breakpoints compared to our previous studies with the parental lines (6,8). The putative breakpoints of the interchange were found to occur within the regions, 6 mGNs in length, located distally to the GAA hybridization site positioned in the long arm of chromosome 2H at 14 mGNs from the centromere, and at the segment confined within outer borders of the Afa family bands localized terminally in the long arm of chromosome 7H, at positions 49 and 61, respectively ( Fig.…”

“…this inversion was produced by gammairradiation of dry seeds of translocation line T-1586 having all chromosome pairs easily distinguishable from each other and selected by means of karyogram analysis of the individual plants in M2. the inversion was introduced to the parental reconstructed karyotypes PK-88 using the "intercross" approach (6). The precise physical mapping of the intrachange breakpoints was decisively facilitated because of the transfer of the distal pericentromeric GAA hybridization signal located at position 11 in the short (satellite) arm ( Fig.…”

“…Giemsa N-banding of the somatic metaphase chromosomes was carried out as previously described (6). the ideograms were constructed on the basis of averages obtained from measurements of at least ten chromosomes of each chromosome type and following the recommendations of Jensen and Lindelaursen (11), and Marthe and Künzel (23): (i) total mitotic length of the genome is defined as "one GeNome"; (ii) the size of the chromosome arms is given in milliGeNomes (mGN), i.e.…”

“…Among the numerous studies dealing with experimental manipulation of the barley karyotype a special interest are those aimed at improving the morphological distinction of the individual chromosome types of the complement (4,5,6,14). Most of the cytologically marked barley karyotypes synthesized so far have been mainly used for investigating the regional specificity of mutagenic agents and the influence of the repositioning of chromosome segments on this phenomenon (7,16,26).…”