Distribution of 45S and 5S rDNA sites in 23 species of Eleocharis (Cyperaceae)
Studies of rDNA location in holocentric chromosomes of the Cyperaceae are scarce, but a few reports have indicated the occurrence of multiple 45S rDNA sites at terminal positions, and in the decondensed state of these regions in prometaphase/metaphase. To extend our knowledge of the number 45S and 5S rDNA sites and distribution in holocentric chromosomes of the Cyperaceae, 23 Brazilian species of Eleocharis were studied. FISH showed 45S rDNA signals always located in terminal regions, which varied from two (E. bonariensis with 2n = 20) to ten (E. flavescens with 2n = 10 and E. laeviglumis with 2n = 60). 5S rDNA showed less variation, with 16 species exhibiting two sites and 7 species four sites, preferentially at terminal positions, except for four species (E. subarticulata, E. flavescens, E. sellowiana and E. geniculata) that showed interstitial sites. The results are discussed in order to understand the predominance of terminal rDNA sites, the mechanisms involved in the interstitial positioning of 5S rDNA sites in some species, and the events of amplification and dispersion of 45S rDNA terminal sites.
KeywordsFISH Holocentric chromosomes rDNA distribution DNA amplification
The authors would like to thank the Brazilian agencies Fundação Araucária and CNPq for financial support. Dr. A. Leyva helped with English editing of the manuscript.
- Govaerts R, Simpson DA, Bruhl JJ, Egorova T, Goetghebeur P, Wilson K (2007) World checklist of Cyperaceae. Kew Publishing, Sedges. KewGoogle Scholar
- Hasterok R, Maluszynska J (2000) Cytogenetic markers of Brassica napus L. chromosome. J Appl Genet 41:1–9Google Scholar
- Hoshi Y (1995) Chromosome studies in Drosera, the Droseraceae in connection with possible origin of the basic chromosome number of x = 10 well-differentiated in the North-hemisphere. Dissertation, Hiroshima UniversityGoogle Scholar
- Schweizer D, Loidl J (1987) A model for heterochromatin dispersion and the evolution of C-banded patterns. Chromosom today 9:61–74Google Scholar