Substantial Genome Size Variation in Taraxacum stenocephalum (Asteraceae, Lactuceae)
- 330 Downloads
There are only a few exceptions to the rule that polyploidy in Taraxacum is associated with agamospermy. One of them is the sexual, tetraploid species Taraxacum stenocephalum. Incidentally, remarkable variation in karyology was found in this species. The present study aims to confirm this variation by an extensive screen of nuclear DNA content. Individuals from two large populations in the Lesser and Greater Caucasus, Georgia were analyzed using flow cytometry to ascertain intraspecific nuclear DNA content variation. Across the whole data set comprising all 159 individuals, a 1.223-fold difference was detected based on propidium iodide (PI) analyses. To verify this finding, we compared flow-cytometric data obtained using DAPI (4′,6-diamidino-2-phenylindole) and PI staining using a representative subset of individuals. This comparison revealed a 1.194-fold difference in DNA content for DAPI and a 1.219-fold difference for PI. Mean nuclear genome size in absolute terms (2C value ± s.d.) was estimated at 4.38 ± 0.21 pg, ranging from 4.01 pg to 4.89 pg, despite the invariable chromosome counts of 2n = 32. A regression analysis comparing the datasets for DAPI and PI staining found a strong correlation between data obtained by the DAPI and PI dyes (R = 0.976; P = 0.0001). Simultaneous high-resolution flow-cytometric analyses also proved the accuracy of our findings. We discuss possible sources of these large differences in DNA content within Taraxacum stenocephalum. Further research is needed to identify the source of this remarkable variation.
KeywordsFlow cytometry Genome size Intraspecific DNA content variation Taraxacum stenocephalum
We wish to thank George Nakhutsrishvili, Otar Abdaladze and other staff of the Institute of Botany of the Georgian Academy of Science, who were instrumental to the success of the expedition, and Eva Ibermajerová who helped with plant cultivation. This project was financially supported by the Czech Science Foundation (206/05/0970) and partly by the Research Plan of the Institute of Botany, Academy of Sciences of the Czech Republic (AV0Z60050516), the Research Plan of the Faculty of Science, Charles University in Prague (MSM 0021620828) and another grant from the Czech Science Foundation (206/08/H049).
- Caceres ME, Pace CD, Mugnozza GTS, Kotsonis P, Ceccarelli M, Cionini PG (1998) Genome size variations within Dasypyrum villosum: correlations with chromosomal traits, environmental factors and plant phenotypic characteristics and behavior in reproduction. Theor Appl Genet 96:559–567CrossRefGoogle Scholar
- Greilhuber J (1988) Critical reassessment of DNA content variation in plants. In Brandham PE (ed) Proceedings of the Third Chromosome Conference. Kew, 1–4 September 1987. H.M.S.O., London, pp 39–50Google Scholar
- Greilhuber J (1997) The problem of variable genome size in plants (with special reference to woody plants). In Borzan Z, Schlarbaum SE (eds) Cytogenetic studies of forest trees and shrub species. Croatian Forests, Inc. and Faculty of Forestry, University of Zagreb, Zagreb, pp 13–34Google Scholar
- Jenkins G, Rees H (1983) Synaptonemal complex formation in a Festuca hybrid. In Brandham PE, Bennett MD (eds) Kew chromosome conference, Vol 2. Allen & Unwin, London, pp 233–242Google Scholar
- Jones RN, Rees H (1982) B chromosomes. Academic Press, New YorkGoogle Scholar
- Kirschner J, Štěpánek J (1993) The genus Taraxacum in the Caucasus. 1, Introduction. 2, The section Porphyrantha. Folia Geobot Phytotax 28:295–320Google Scholar
- Piegu B, Guyot R, Picault N, Roulin A, Saniyal A, Kim H, Collura K, Brar DS, Jackson S, Wing RA, Panaud O (2006) Doubling genome size without polyploidization: Dynamics of retrotransposition-driven genomic expansions in Oryza australiensis, a wild relative of rice. Genome Res 16:1262–1269PubMedCrossRefGoogle Scholar
- Roux N, Toloza A, Radecki Z, Zapata-Arias FJ, Doležel J (2003) Rapid detection of aneuploidy in Musa using flow cytometry. Pl Cell Rep 21:483–490Google Scholar
- Šmarda P, Bureš P (2010) Understanding intraspecific variation in genome size in plants. Preslia 82:41–61Google Scholar
- Vicient CM, Suoniemi A, Anamthawat-Jonsson K, Tanskanen J, Beharav A, Nevo E, Schulman AH (1999) Retrotransposon BARE-1 and its role in genome evolution in the genus Hordeum. Pl Cell 11:1769–1784Google Scholar