Holocentric Chromosomes of <i>Luzula elegans</i> Are Characterized by a Longitudinal Centromere Groove, Chromosome Bending, and a Terminal Nucleolus Organizer Region

Abstract

The structure of holocentric chromosomes was analyzed in mitotic cells of Luzula elegans. Light and scanning electron microscopy observations provided evidence for the existence of a longitudinal groove along each sister chromatid. The centromere-specific histone H3 variant, CENH3, colocalized with this groove and with microtubule attachment sites. The terminal chromosomal regions were CENH3-negative. During metaphase to anaphase transition, L. elegans chromosomes typically curved to a sickle-like shape, a process that is likely to be influenced by the pulling forces of microtubules along the holocentric axis towards the corresponding microtubule organizing regions. A single pair of 45S rDNA sites, situated distal to Arabidopsis-telomere repeats, was observed at the terminal region of one chromosome pair. We suggest that the 45S rDNA position in distal centromere-free regions could be required to ensure chromosome stability.

Anti-Phosphorylated Histone H2AThr120: A Universal Microscopic Marker for Centromeric Chromatin of Mono- and Holocentric Plant Species

“…Both Juncaceae species show a continuous distribution of CENH3 along almost the entire length of mitotic metaphase chromosomes Heckmann et al, 2011]. A similar centromerelike distribution was found for anti-H2AThr120ph at metaphase ( fig.…”

Holocentromeres inRhynchosporaare associated with genome-wide centromere-specific repeat arrays interspersed among euchromatin

“…In both cases, a longitudinal CENH3-positive centromere structure was observed during mitosis. In the rush Luzula (Juncaceae), the longitudinal centromere forms a groove (here referred as the "centromere groove") in each sister chromatid along almost the whole metaphase chromosome except for the most terminal regions (9)(10)(11). Recently, a similar centromere organization was found in the sedge species Rhynchospora pubera (12).…”

Holocentric chromosomes: convergent evolution, meiotic adaptations, and genomic analysis

“…The genome of C. elegans contains few tandem repeats (Hillier et al 2007), but this is not the case for all genomes of species with holocentric chromosomes (Table 1), e.g., in the snowy woodrush L. nivea and its close relative L. elegans (Nagaki et al 2005;Heckmann et al 2011). In contrast to C. elegans, a high-copy 178-bp tandem repeat was found in the genome of L. nivea (Haizel et al 2005).…”