Ribosomal DNA locus evolution in Nemesia: transposition rather than structural rearrangement as the key mechanism?
- 175 Downloads
We investigated chromosome evolution in Nemesia using fluorescent in-situ hybridization (FISH) to identify the locations of 5S and 45S (18–26S) ribosomal genes. Although there was conservation between Nemesia species in chromosome number, size and centromere position, there was large variation in both number and position of ribosomal genes in different Nemesia species (21 different arrangements of 45S and 5S rRNA genes were observed in the 29 Nemesia taxa studied). Nemesia species contained between one and three pairs of 5S arrays and between two and four pairs of 45S arrays. These were either sub-terminally or interstitially located and 45S and 5S arrays were often located on the same chromosome pair. Comparison of the positions of rDNA arrays with meiotic chromosome behaviour in interspecific hybrids of Nemesia suggests that some of the changes in the positions of rDNA have not affected the surrounding chromosome regions, indicating that rDNA has changed position by transposition. Chromosome evolution is frequently thought to occur via structural rearrangements such as inversions and translocations. We suggest that, in Nemesia, transposition of rDNA genes may be equally if not more important in chromosome evolution.
Key wordschromosome evolution 5S and 45S rDNA fluorescence in-situ hybridization Nemesia Scrophulariaceae
Unable to display preview. Download preview PDF.
- Bolkhovskikh Z, Grif V, Matwejeva T, Zakharyeva O (1969) Chromosome Numbers of Flowering Plants. Leningrad: USSR Academy of Sciences.Google Scholar
- Datson PM, Murray BG (2003) The use of in situ hybridisation to investigate plant chromosome diversity. In Sharma AK, Sharma A, eds., Plant Genome: Biodiversity and Evolution, Vol. 1, Part A. Enfield, NH: USA Science Publishers, pp. 298–318.Google Scholar
- Datson PM, Murray BG, Hammett KRW (2006a) Pollination systems, hybridization barriers and meiotic chromosome behaviour in Nemesia hybrids. Euphytica 151: 173–185.Google Scholar
- Datson PM, Murray BG, Steiner KE (2006b) Climate and the evolution of annual/perennial life-histories in Nemesia (Scrophulariaceae) Pl Sys Evol (in press).Google Scholar
- Hizume M (1993) Chromosome localization of 5s rRNA genes in Vicia faba and Crepis capillaris. Cytologia 58: 417–421.Google Scholar
- Jürgens N (1991) A new approach to the Namib region. Part 1. Phytogeographic subdivision. Vegetatio 97: 21–38.Google Scholar
- La Cour LF (1945) In Darlington CD, Janaki Ammal EK, eds., Chromosome Atlas of Cultivated Plants. London: George Allen & Unwin 315p.Google Scholar
- Levin DA (2002) The Role of Chromosome Change in Plant Evolution. Oxford: Oxford University Press.Google Scholar
- Ornduff R (1969) Index to plant chromosome numbers for 1967. Regnum Vegetabile 59: 94.Google Scholar
- Sambrook J, Russell DW (2001) Molecular Cloning: a Laboratory Manual, 3rd edn. Cold Spring Harbor, NY: Cold Spring Harbor Laboratory Press.Google Scholar
- Schwarzacher T, Heslop-Harrison JS (2000) Practical In Situ Hybridization. Oxford: BIOS Scientific Publishers.Google Scholar
- Sýkorová E, Fajkus J, Mezníková et al. (2006) Minisatellite telomeres occur in the family Alliaceae but are lost in Allium. Am J Bot 93: 814–823.Google Scholar
- White MJD (1973) Animal Cytology and Evolution. Cambridge: Cambridge University Press.Google Scholar