• MeSH
• DNA chloroplastová genetika   MeSH
• DNA primery genetika   MeSH
• fylogeneze MeSH
• intergenová DNA genetika   MeSH
• mutace genetika   MeSH
• polymorfismus genetický MeSH
• pseudogeny genetika   MeSH
• Publikační typ
• srovnávací studie MeSH

The genus Luzula consists of 115 species distributed throughout the world. Luzula is monophyletic, but species relationships within the genus are difficult to determine primarily due to the similar morphology even within geographically remote taxa (especially within the section Luzula). The plastome trnL intron, trnL-F intergenic spacer and the nuclear ribosomal ITS1-5.8S-ITS2 regions were analysed using maximum parsimony and maximum likelihood reconstruction in 93 species of Luzula. The incongruent phylogenetic signals obtained from the chloroplast and the nuclear genomes point to incomplete lineage sorting as well as recent hybridisation in this group. Although tree-building analyses revealed several well-supported lineages, the outcomes for many groups were ambiguous. In the total evidence tree, Luzula species were grouped within six main clades (1. subgenus Marlenia, 2. subgenus Pterodes except for L. pilosa, 3. sections Anthelaea and Nodulosae, 4. sections Diprophyllatae and Thyrsanochlamydeae, 5. section Alpinae except for a few species and 6. section Luzula). The subgenus Marlenia occupies the early derived lineage within the genus Luzula. The traditionally accepted subgenera Pterodes and Luzula (and its sections) appear to be non-monophyletic. A statistical parsimony network approach showed that ancient haplotypes and ribotypes co-occur with their descendants in Luzula. Furthermore, many haplotypes are shared among different species. Within the Luzula section Luzula, both recent hybridisation and incomplete lineage sorting of ancestral polymorphisms may represent potential sources of the incongruence between chloroplast and nuclear data.

• MeSH
• DNA chloroplastová genetika   MeSH
• DNA rostlinná genetika   MeSH
• fylogeneze MeSH
• Magnoliopsida klasifikace   genetika   MeSH
• polymerázová řetězová reakce MeSH
• pravděpodobnostní funkce MeSH
• ribozomální DNA genetika   MeSH
• sekvenční analýza DNA MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

BACKGROUND AND AIMS: The centromere drive theory explains diversity of eukaryotic centromeres as a consequence of the recurrent conflict between centromeric repeats and centromeric histone H3 (CenH3), in which selfish centromeres exploit meiotic asymmetry and CenH3 evolves adaptively to counterbalance deleterious consequences of driving centromeres. Accordingly, adaptively evolving CenH3 has so far been observed only in eukaryotes with asymmetric meiosis. However, if such evolution is a consequence of centromere drive, it should depend not only on meiotic asymmetry but also on monocentric or holokinetic chromosomal structure. Selective pressures acting on CenH3 have never been investigated in organisms with holokinetic meiosis despite the fact that holokinetic chromosomes have been hypothesized to suppress centromere drive. Therefore, the present study evaluates selective pressures acting on the CenH3 gene in holokinetic organisms for the first time, specifically in the representatives of the plant genus Luzula (Juncaceae), in which the kinetochore formation is not co-localized with any type of centromeric repeat. METHODS: PCR, cloning and sequencing, and database searches were used to obtain coding CenH3 sequences from Luzula species. Codon substitution models were employed to infer selective regimes acting on CenH3 in Luzula KEY RESULTS: In addition to the two previously published CenH3 sequences from L. nivea, 16 new CenH3 sequences have been isolated from 12 Luzula species. Two CenH3 isoforms in Luzula that originated by a duplication event prior to the divergence of analysed species were found. No signs of positive selection acting on CenH3 in Luzula were detected. Instead, evidence was found that selection on CenH3 of Luzula might have been relaxed. CONCLUSIONS: The results indicate that holokinetism itself may suppress centromere drive and, therefore, holokinetic chromosomes might have evolved as a defence against centromere drive.

• MeSH
• centromera genetika   MeSH
• chromozomy rostlin genetika   MeSH
• fylogeneze MeSH
• genom rostlinný genetika   MeSH
• histony genetika   MeSH
• Magnoliopsida genetika   MeSH
• meióza genetika   MeSH
• sekvenční analýza DNA MeSH
• sekvenční seřazení MeSH
• selekce (genetika) genetika   MeSH
• Publikační typ
• časopisecké články MeSH