Differential amplification of satellite PaB6 in chromosomally hypervariable Prospero autumnale complex (Hyacinthaceae).
Bottom Line: This study addresses genomic changes associated with the extensive chromosomal variation of the Mediterranean Prospero autumnale complex (Hyacinthaceae), which includes four diploid cytotypes each with a unique combination of chromosome number (x = 5, 6, 7), rDNA loci and genome size.Additionally, two lineages of cytotype B(7)B(7) (x = 7), possessing either a single or duplicated 5S rDNA locus, differ in PaB6 copy number; the ancestral condition of a single locus is associated with higher PaB6 copy numbers.The evolution of the PaB6 copy numbers is discussed, and it is suggested that PaB6 represents a recent and highly dynamic system originating from a small pool of ancestral repeats.
Affiliation: Department of Botany and Biodiversity Research, University of Vienna, Rennweg 14, A-1030 Vienna, Austria.Show MeSH
Mentions: Copy numbers were estimated by quantitative chemiluminescent dot blot hybridization of labelled PaB6 as probe against known quantities of genomic DNAs of all three species and four cytotypes (Fig. 3A). Large differences in the genomic content of PaB6 between the four cytotypes of P. autumnale corroborated the results of Southern blot experiments and of FISH (Figs 3B–D and 4). The probe hybridized strongly to genomic DNA of cytotype B6B6 (Fig. 3A–C), moderately to cytotype B5B5 (Fig. 3A, C) and weakly to some individuals of cytotype B7B7 (Fig. 3A, B, D). A very weak signal was detected in genomic DNA of cytotype AA (Fig. 3A). The PaB6 probe hybridized only very weakly to DNAs of P. hanburyi and P. obtusifolium (Fig. 3A). The highest copy number was found in cytotype B6B6 with 1·8-2·1 × 106 copies per haploid genome (7–10 %), followed by cytotype × B5B5 with 1·2-1·4 × 106 copies/1C (6–7 %). One accession of cytotype B7B7 had 2·1-2·5 × 104 copies/1C (approx. 0·13 %), while AA had 1·8–2·6 × 104 copies/1C (approx. 0·08 %; Table 1, Fig. 3A). A variant of the B7B7 cytotype, carrying a single 5S rDNA locus on chromosome 1 and stronger signals of PaB6 in all chromosomes, could not be analysed due to lack of appropriate quality plant material. Prospero obtusifolium and P. hanburyi possessed only very low amounts of PaB6, below the slot blot detection limit.
Affiliation: Department of Botany and Biodiversity Research, University of Vienna, Rennweg 14, A-1030 Vienna, Austria.