Ribosomal, telomeric and heterochromatin sequences localization in the karyotype of Anemone hortensis

Abstract

Karyotype of the Mediterranean species Anemone hortensis L. (Ranunculaceae) was characterized with emphasis on heterochromatin distribution and localization of ribosomal (18S-5.8S-26S and 5S rDNA) and telomeric repeats (TTTAGGG). Diploid chromosome complement, 2n = 2x = 16, common to all investigated populations consisted of three acrocentric, one meta-submetacentric and four metacentric chromosomes ranging in size from 6.34 to 10.47 m ; ; m. Fluorescence in situ hybridization (FISH) with 18S and 5S rDNA probes revealed two 18S-5.8S-26S rDNA loci on satellite and secondary constriction (SC) of acrocentric chromosome pair 2 and terminally on accrocentric chromosome pair 3, and two 5S rDNA loci in pericentromeric region of meta-submetacentric chromosome pair 4 and in the proximity to 18S-5.8S-26S rDNA locus on chromosome pair 2. The only GC rich heterochromatin, as revealed by fluorochrome Chromomycin A3 (CMA) staining, was that associated with nucleolar organizer regions (NORs), while AT rich heterochromatin, stained with 4, 6-diamino-2-phenylindole (DAPI), was distributed intercalarly and terminally on the long arm of all three acrocentric chromosomes, and terminally on chromosomes 4 and 5. FISH with Arabidopsis-type of telomeric repeats (TTTAGGG) as a probe revealed two classes of signals, small dot-like and large bands, at chromosome termini exclusively, where they corresponded to terminal DAPI stained heterochromatin. Heteromorphism of chromosome pair 4 which refers to terminal DAPI bands and FISH signals was observed in populations of A. hortensis. Chromosome pairing during meiosis was regular with formation of localized chiasmata proximal to the centromere.