FISH physical mapping of 5S rDNA and telomere sequence repeats identified a peculiar chromosome mapping and mutation in Leucanthemella linearis and Nipponanthemum nipponicum in Chrysanthemum sensu lato

Abstract

Using FISH biotin-labeled-probe of 5S rDNA showed a peculiar FISH signals on the chromosomes of Leucanthemella linearis and Nipponanthemum nipponicum. At the time of using the probe of 5S rDNA after PCR-amplification using genomic DNA of Chrysanthemum boreale (=Dendranthema boreale), six and two FISH signals of 5S rDNA were co-localized with the 45S rDNA regions of sat-chromosomes in the chromosome complement of both L. linearis and N. nipponicum, respectively. Using the probe of the 5S rDNA after PCR-amplification using genomic DNA of N. nipponicum, those FISH signals were two interstitial signals of 5S rDNA sites on two chromosomes of each chromosome complement as well as six and two FISH signals were co-localized with the 45S rDNA regions of sat-chromosomes of both L. linearis and N. nipponicum, respectively. The chromosomes of N. nipponicum also showed a peculiar FISH signals at terminal regions of most chromosomes. FISH signals of telomere sequence repeats were detected on terminal regions all chromosomes of N. nipponicum, while L. linearis showed terminal and interstitial FISH signals indicating existence of chromosomal mutation as translocation and or inversion. The size of the FISH terminal signals of the 5S rDNA sites was not associated or co-localized with the telomeric signals in the chromosomes of N. nipponicum. Use of FISH facilitates the identification of homologous chromosomes and the inference of changes in genome structure among the species. In the present study, the FISH signals that showed the phenomenon of co-localization of the 5S rDNA site with 45S rDNA were detected for the first time. The species genome appears to have undergone structural reorganization and recombination and, thus, formed unique characteristics as a new genome of the species.