Abstract Detail

Chromosome and Karyotype Evolution in Plants

Marques, André [1].

All around centromeres: Karyotype and genome evolution in plants with repeat-based holocentromeres.

Most studied organisms are defined by one single site-restricted centromere per chromosome (monocentric chromosome) visible as primary constriction during metaphase. However, in independent eukaryotic lineages species with holocentric chromosomes exist. Holocentric chromosomes have no distinct primary constriction visible at metaphase. Spindle fibres are attached along almost the entire (Greek: holo-) poleward surface of the chromatids. As a result, sister chromatids migrate to opposite poles parallel to each other during anaphase, while in case of monocentric chromosomes microtubule spindles attach to a distinct kinetochore and the sister chromatids move to the poles at anaphase with the centromere leading. We have recently started to build the first reference chromosome-level genomes for a holocentric plant. Incredibly, only in a single clade of the holocentric genus Rhynchospora we found three different genomic features in the first three genomes sequenced. Solid evidences for genome plasticity likely deriving from the centromere structure in these organisms challenges the so far function and evolution models currently proposed. First, whole genome duplications events are observed without basal chromosome number change neither gene copy number reduction. Second, fully achiasmatic species present a novel type of clonal seed propagation, however, maintaining the full meiotic division and egg fertilization. Third, large heteromorphisms are present between homologs and megabase-size INDELs are observed between homologs. Finally, recent ChIPseq with histone modifications and the centromere protein CENH3 reveals that the repeat-based holocentromere genomes in this group have a very fine-scale regulation of chromatin states, in contrast to monocentric genomes, where the chromosomes are largely divided in eu- and heterochromatic domains. Our results provide very solid knowledge about karyotype and genome evolution in plants with holocentric chromosomes.

1 - MPIPZ, Department of Chromosome Biology, Carl-von-Linné-Weg 10, Cologne, Andere, 50829, Germany

Keywords:
Holocentric chromosomes
Whole genome duplication
genome evolution
genome regulation
karyotype evolution.

Presentation Type: Colloquium Presentations
Session: C11, Chromosome and Karyotype Evolution in Plants
Location: /
Date: Friday, July 23rd, 2021
Time: 10:30 AM(EDT)
Number: C11003
Abstract ID:268
Candidate for Awards:None