Localization of 45S and 5S rDNA on Chromosomes of <i>Nigella damascena</i>, Ranunculaceae

Abstract

Summary Nigella damascena has 2n=12 chromosomes composed of five long metacentric chromosome pairs and a short telocentric chromosome pair. FISH using rDNA probes was applied on the chromosomes of this species. 45S rDNA were located at the terminal region of three pairs of long metacentric chromosomes and a pair of short chromosomes. 5S rDNA appeared at the interstitial regions of the short arm of two long metacentric chromosomes. Chromosome, FISH, Nigella damascena, 45S and 5S rDNA. Nigella damascena is one of the 14 species that belong to the genus Nigella. It is planted in gardens all over Japan as an ornamental plant. The Nigella species are diploid and its genome (2n=12) has five pairs of long metacentric chromosomes and a short telocentric pair. Therefore, these species were used preferentially in early studies for the early stages of comparative karyotype analysis to study plant chromosome structures and the effects of mutagens or irradiation on chromosomes (Gregory 1941, Kurita 1956, 1959, Moutschen-Dahmen and Moutschen-Dahmen 1965, Moutschen 1968, Moutschen et al. 1969, Marks 1975. Previous studies showed the karyotype, localization of heterochromatin or C-bands (Marks 1975), NORs by silver staining (Hizume et al. 1982), and fluorescent bands by base-specific fluorochromes (Hizume et al. 1989). Modern methods have not been applied to the chromosomes of this species at all. The location of rRNA genes has not been reported until now. We report the locations of 45S rDNA and 5S rDNA on the chromosomes by using FISH, and compare them with previous chromosome studies. Key words Materials and methodsSeeds of Nigella damascena cv. Persian Jewel were obtained commercially from Sakata Seed Company. The seeds were germinated on wet filter paper in the dark at 20 o C. The primary root tips were collected and treated in 0.05% colchicine for 3 h then fixed in acetic alcohol (1 : 3). Chromosomes were prepared by enzymatic maceration in 1% Pectolyase Y-23 and 4% Cellulase R10 at 37 o C for 30-40 min, followed by air or flame drying. rDNAs were amplified by the CTAB method using genomic DNA extracted from young leaves of the species as the template. DNAs were labeled with biotin or digoxigenin and used as probes for two-color FISH. The PCR, labeling, and FISH procedures are conducted according to a previous report (Hizume et al. 2002). Chromosome images and FISH signal features were captured by a cooled CCD camera, and the images were processed using IPLab software.

A simple non-toxic ethylene carbonate fluorescence in situ hybridization (EC-FISH) for simultaneous detection of repetitive DNA sequences and fluorescent bands in plants

“…1c), and V. faba (Fig. 1d–e) conformed to the rDNA chromosomal pattern already described by other authors (Hizume 1992, 1993; Shibata and Hizume 2002; Raina et al 2010; Hizume et al 2013). The novel findings include (i) the 18S-5.8S-26S rDNA locus of chromosome pair 3 in N. damascena occupies intercalary position (Fig.…”

The Aquilegia genome provides insight into adaptive radiation and reveals an extraordinarily polymorphic chromosome with a unique history

“…In the three T-type species tested here, the 35S is proximal to the centromere, a localization seen for only 3.5% of 35S sites reported in higher plants ( Roa and Guerra, 2012 ). In contrast, all R-type species examined have terminal or subterminal 45S loci ( Hizume et al, 2013 ; Mlinarec et al, 2006 ; Weiss-Schneeweiss et al, 2007 ; Liao et al, 2008 ). Given that 35S repeats can be fragile sites ( Huang et al, 2008 ) and 35S rDNA clusters and rearrangement breakpoints co-localize ( Cazaux et al, 2011 ), a 35S-mediated chromosomal break could explain differences in base chromosome number between R-type and T-type species.…”

Giemsa C-banding Karyotype and Detection of Polymorphic Constitutive Heterochromatin in <i>Nigella sativa</i> L.

“…Secondary constrictions in more than one pair have also been found in other Nigella species, e.g., N. damasence and N. orientalis (Gilot-Delhalle et al 1976, Datta and Saha 2003, Hizume et al 1982, 2013. The number and position of NORs can thus serve as a landmark for the identification of a particular chromosome.…”