Molecular cytogenetic characterization of the 5S ribosomal DNA (rDNA) was performed in a lynx spider Oxyopes sertatus. The 5S rDNA repeat sequence was determined by PCR-based cloning and subsequent sequence analysis: one unit was approximately 3670 bp in length, of which 3550 bp, a non-transcribed spacer (NTS), contained a full length of the histone H2B-like gene attached with the 5' flanking region essential for the transcription. This introduction of histone H2B-like gene into 5S rDNA cluster had never been reported in previous studies. Then, we mapped the chromosomal locations of the 5S rDNA by fluorescence in situ hybridization (FISH), and identified sites on three different chromosomes. We discuss on the linkages of 5S rDNA with multigene families including histone H2B-like gene.
As a part of our programme to explore and evaluate genetic diversity of flowering plants from Kashmir Himalayas, at present 150 species of Polypetalae have been meiotically worked out. It brings to light new/ varied chromosome number reports for 30 species. The taxa being cytologically worked out for the first time on world-wide basis include four species as Pleurospermum densiflorum (n=11), Sedum wallichianum (n=36), Astragalus strobiliferus (n=8), Hedysarum cachemirianum (n=8) and one variety as Rosa macrophylla var. minor (n=7) along with new intraspecific cytoypes in case of six species as Cardamine loxostemonoides (n=8), Fumaria indica (n=6), G. ocellatum (n=14), Rosa pendulina (n=7), Sedum ewersii (n=36) and Sisymbrium orientale (n=14). Nineteen species which are being cytologically worked out for the first time from India include Barbarea intermedia (n=8), Corydalis cashmeriana (n=8), Descurainia sophia (n=10), Epilobium alpinum (n=9), E. angustifolium (n=18 and 36), E. cylindricum (n=18), E. hirsutum (n=18), E. palustre (n=9), Geranium sibiricum (n=14), Hypericum perforatum (n=16), Impatiens bicornuta (n=9), Lupinus polyphyllus (n=24), Oenothera drummondii (n=7), Rorippa islandica (n=8), Sisymbrium strictum (n=7), Rubus caesius (n=7), R. idaeus (n=7), R. saxatilis (n=14) and Myricaria germanica (n=12).
RBMX is an RNA-binding motif protein identified as a component of purified human metaphase chromosomes. We have analyzed the functional significance of RBMX by electron microscopy (EM) in combination with RNA interference (RNAi). We revealed that depletion of RBMX results in the accumulation of mitotic cells. EM investigation further showed that RBMX depletion leads to an increase in the fuzzy ball structure that is reminiscent of the prekinetochore. It is most probably due to the result of disruption at early stages of kinetochore maturation, so that kinetochore differentiation into the authentic trilaminar morphology is disturbed. The present EM data illuminated the importance of RBMX in kinetochore formation for subsequent stable microtubules interaction.
Zebularine, cytidine analog is known as DNA methylation inhibitor such as 5-azacytidine and 5-aza-2'-deoxycytidine, and it is more stable in aqueous solution than 5-azacytidine and 5-aza-2'-deoxycytidine. We investigated effects of zebularine on plant mitotic chromosomes. A wheat disomic addition line carrying a pair of alien chromosomes (Leymus racemosus chromosome l) was treated with zebularine at various concentrations. The alien chromosomes were discriminated from the wheat chromosomes by genomic in situ hybridization, facilitating observation of any rearrangements between the wheat and alien chromosomes. Root growth was obviously inhibited by zebularine because of reduction of the mitotic division cells. Rearrangements such as ring chromosomes, insertions, deletions, and translocations were observed in the treated mitotic chromosomes. The aberrations were increased in a concentration-dependent manner of zebularine.
Although Torenia fournieri (Linderniaceae) and Torenia baillonii carry 2n=18 and 2n=16 chromosomes, respectively, their F1 hybrid showed eight bivalent chromosomes with chiasmata as a result of interspecific pairing and one univalent chromosome from T. fournieri. To elucidate the behavior of the chromosomes in the amphidiploids, we developed a simple method of chromosome doubling by the application of colchicine combined with the induction of adventitious buds in detached leaves. The frequency of polyploid plants was highest (8%) in the treatment with 15 μmol mol-1 colchicine for 2 days. The meiocytes of the amphidiploids showed extent pairing (i.e., the appearance of bivalent and multivalent chromosomes), including intraspecific and interspecific pairings. This result supports the hypothesis that T. fournieri and T. baillonii have eight homologous chromosomes and that T. fournieri possesses an extra chromosome of unknown origin.
The present day edible bananas are either diploids or triploids or rarely tetraploids with a vast combination of A and B genomes obtained from the two wild diploid species Musa acuminata and M. balbisiana through intraand interspecific hybridizations. A simple protocol for obtaining meiotic metaphase plates of some Musa cultivars has been described in this paper. Structural alterations of the chromosomes in these cultivars were studied to assess the genomic constituents. Pairing variability was observed in the different cultivars with the occurrence of multivalent structures in the allotriploids indicating segmental homology or homeologous pairing among the A and B genome of M. acuminata and M. balbisiana probably due to common ancestry of the two wild species.
Cytological investigations on myco-heterotrophic orchid of Gastrodia javanica (Blume) Lindl. were carried out. The chromosome number of 2n=36 was counted here for the first time. The chromosome complement at resting stage showed the intermediate type between the simple chromocenter type and the complex chromocenter type. The metaphase chromosomes showed a bimodal karyotype in length consisted with four large chromosomes varied from 2.0-1.7 μm and 32 small chromosomes varied from 1.4-0.8 μm. The chromosome number of 2n=36 was equal to 2n=36=18II in G. elata Blume and n=18 in G. angusta S. Chow & S. C. Chen, and it differed from 2n=22 in G. confusa Honda & Tuyama and G. pubilabiata Sawa.