Cytogenetic characterization and nuclear DNA content of three North African endemic Centaurea species

Abstract

Three endemic Centaurea species from North Africa are investigated for the first time by chromomycin fluorochrome banding for GC-rich DNA distribution, fluorescence in situ hybridization for physical mapping of rRNA genes, and flow cytometry for genome-size assessment. Investigated species belong to three different sections and possess three basic chromosome numbers: C. tougourensis subsp. tougourensis 2n = 4x = 36 (x = 9), C. musimonum 2n = 2x = 20 (x = 10), and C. maroccana 2n = 2x = 24 (x = 12). The number and distribution of chromomycin positive bands (CMA⁺) and 18S-5.8S-26S (35S) rDNA loci were different among investigated species and ranged from 6 to 80 chromomycin bands and from 2 to 6 35S rDNA loci. The three species have just one 5S rDNA locus at intercalary position on a separate chromosome pairs, except in the case of C. musimonum in which both rDNA loci were localized on the same chromosome. All rDNA loci were co-localized with CMA⁺ bands, except three 35S in C. musimonum. Genome size ranged from 2C = 1.66 to 2C = 2.86 pg in diploid species (C. musimonum and C. maroccana, respectively) and to 2C = 4.51 pg in tetraploid C. tougourensis subsp. tougourensis.

Keywords::

• Fluorescent in situ hybridization
• fluorochrome banding
• genome size
• heterochromatin
• karyotype
• 5S and 35S rRNA genes

Acknowledgements

The authors are grateful to R. Djeghar (Génétique Biochimie et Biotechnologies Végétales, Université Constantine 1, Constantine, Algérie) for technical assistance in classical cytogenetics, O. Robin (Ecologie, Systématique, et Evolution, Université Paris-Sud, Orsay, France) for technical support in molecular cytogenetics, and M. Bourge for his assistance on the IBiSA Cytometry Platform of the Imagif Cell Biology Unit of the Gif campus (www.imagif.cnrs.fr). The authors also thank Samuel Pyke for improving the English and two anonymous reviewers for their valuable comments to improve the quality of the paper.

Additional information

Funding

This work was partially supported by the NATO – Science for Peace and Security Programme [Collaborative Linkage Grant number 983838].