Mega-sized pericentromeric blocks of simple telomeric repeats and their variants reveal patterns of chromosome evolution in ancient Cycadales genomes

0563711 - BFÚ 2023 RIV GB eng J - Článek v odborném periodiku
Vozárová, Radka - Wang, W. - Lunerová Bedřichová, Jana - Shao, F.Q. - Pellicer, J. - Leitch, I. J. - Leitch, A. R. - Kovařík, Aleš
Mega-sized pericentromeric blocks of simple telomeric repeats and their variants reveal patterns of chromosome evolution in ancient Cycadales genomes.
Plant Journal. Roč. 112, č. 3 (2022), s. 646-663. ISSN 0960-7412. E-ISSN 1365-313X
Grant CEP: GA ČR(CZ) GA22-16826S
Institucionální podpora: RVO:68081707
Klíčová slova: telomeres * genome evolution * chromosome rearrangements * Cycadaceae * gymnosperms
Obor OECD: Plant sciences, botany
Impakt faktor: 7.2, rok: 2022
Způsob publikování: Open access
https://onlinelibrary.wiley.com/doi/10.1111/tpj.15969

Simple telomeric repeats composed of six to seven iterating nucleotide units are important sequences typically found at the ends of chromosomes. Here we analyzed their abundance and homogeneity in 42 gymnosperm (29 newly sequenced), 29 angiosperm (one newly sequenced), and eight bryophytes using bioinformatics, conventional cytogenetic and molecular biology approaches to explore their diversity across land plants. We found more than 10 000-fold variation in the amounts of telomeric repeats among the investigated taxa. Repeat abundance was positively correlated with increasing intragenomic sequence heterogeneity and occurrence at non-telomeric positions, but there was no correlation with genome size. The highest abundance/heterogeneity was found in the gymnosperm genus Cycas (Cycadaceae), in which megabase-sized blocks of telomeric repeats (i.e., billions of copies) were identified. Fluorescent in situ hybridization experiments using variant-specific probes revealed canonical Arabidopsis-type telomeric TTTAGGG repeats at chromosome ends, while pericentromeric blocks comprised at least four major telomeric variants with decreasing abundance: TTTAGGG>TTCAGGG >TTTAAGG>TTCAAGG. Such a diversity of repeats was not found in the sister cycad family Zamiaceae or in any other species analyzed. Using immunocytochemistry, we showed that the pericentromeric blocks of telomeric repeats overlapped with histone H3 serine 10 phosphorylation signals. We show that species of Cycas have amplified their telomeric repeats in centromeric and telomeric positions on telocentric chromosomes to extraordinary high levels. The ancestral chromosome number reconstruction suggests their occurrence is unlikely to be the product of ancient Robertsonian chromosome fusions. We speculate as to how the observed chromosome dynamics may be associated with the diversification of cycads.
Trvalý link: https://hdl.handle.net/11104/0340549