engleski

The Repetitive DNA Composition in the Natural Pesticide Producer Tanacetum cinerariifolium (Asteraceae): Interindividual Variation of Subtelomeric Tandem Repeats

Dalmatian pyrethrum (Tanacetum cinerariifolium (Trevir.) Sch. Bip.), a plant species endemic to the east Adriatic coast, is used worldwide for production of the organic insecticide, pyrethrin. Our study aims are to identify, classify, and characterize repetitive DNA in the T. cinerariifolium genome using clustering analysis of a low coverage genomic dataset. Repetitive DNA represents about 71.63% of the genome. Retrotransposons were the most abundant elements, representing 54.23% of the genome. Fluorescence in situ hybridization revealed that Ty3-gypsy retrotransposons from the Athila and Tekay lineages had similar patterns of chromosomal distribution ; being distributed on every chromosome almost along the entire chromosome length, except for the subterminal heterochromatic regions, which appeared to be retrotransposon-poor. In contrast, the subterminal heterochromatic regions are enriched with satellite DNA families, TcSAT1 and TcSAT2, while the third family, TcSAT3, is positioned intercalary on two chromosome pairs. T. cinerariifolium exhibits linked 5S and 35S rDNA configuration (L-type). All three 35S/5S loci were polymorphic. FISH reveals amplification of interstitial telomeric repeats (ITRs) in T. cinerariifolium. Each homologue chromosome pair posesses unique ITRs pattern. By screening a large number of individuals FISH reveals that, contrary to the stable ITRs pattern, the subtelomeric regions of T. cinerariifolium are highly polymorphic. Physical contacts of chromosome ends in meiosis (indicative of material exchange) suggest that in addition to outcrossing (T. cineerarifoliium is an obligate oucrosser), polymorphism was also caused by both intra- and interchromosomal recombination. Altogether, our data highlights the dynamic nature of DNA sequences associated with subtelomeres in T. cinerariifolium and suggests that subtelomeres represent one of the most dynamic and rapidly evolving regions in eukaryotic genomes.

Repetitive DNA, Tanacetum cinerariifolium, interstitial telomeric repeats, subtelomeric heterochromatin

nije evidentirano