Molecular analysis of holocentric centromeres of <i>Luzula</i> species

Abstract

Luzula spp, like the rest of the members of the Juncaceae family, have holocentric chromosomes. Using the rice 155-bp centromeric tandem repeat sequence (RCS2) as a probe, we have isolated and characterized a 178-bp tandem sequence repeat (LCS1) from Luzula nivea. The LCS1 sequence is present in all Luzula species tested so far (except L. pilosa) and like other satellite repeats found in heterochromatin, the cytosine residues are methylated within the LCS1 repeats. Using fluorescent in situ hybridization (FISH) experiments we have shown that there are at least 5 large clusters of LCS1 sequences distributed at heterochromatin regions along each of the 12 chromosomes of L. nivea. We have shown that a centromeric antibody Skp1 co-localizes with these heterochromatin regions and with the LCS1 sequences. This suggests that the LCS1 sequences are part of regions which function as centromeres on these holocentric chromosomes. Furthermore, using the BrdU assay to identify replication sites, we have shown that these heterochromatin sites containing LCS1 associate when being replicated in root interphase nuclei. Our results also show premeiotic chromosome association during anther development as indicated by single-copy BAC in situ and the presence of fewer LCS1 containing heterochromatin sites in these cells.

Chromosome Centromeres: Structural and Analytical Investigations with High Resolution Scanning Electron Microscopy in Combination with Focused Ion Beam Milling

“…The lack of a primary constriction in holocentric chromosomes, here represented by Luzula spp. , is well characterized [Braselton, 1971;Gernand et al, 2003;Haizel et al, 2005;Guerra et al, 2006]. In Luzula nivea putative centromeric DNA sequences have been located for light microscopy at local areas along the whole chromosome [Haizel et al, 2005].…”

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). This repeat formed at least five distinct arrays per chromosome when studied by FISH.…”

“…Similarly, inverted meiosis seems to feature spindle attachment sites that are spread along the length of meiotic chromosomes and may assemble on unique sequences in many holocentric organisms. Only in holocentric organisms such as L. nivea, which has tandem repeats underlying cenH3 binding sites, is it possible for centromere DNA to evolve rapidly in the same manner as it does in monocentric chromosomes (Haizel et al 2005). Luzula has inverted meiosis with distributed kinetochore activity.…”

Nuclear architecture and chromosome dynamics in the search of the pairing partner in meiosis in plants

“…Functionally equivalent domains like centromeres or telomeres that exist in all chromosomes represent appropriate starting points for the initiation of interactions in the homology search. Centromeres associate at leptotene in many organisms (Church and Moens, 1976;Bennett, 1979;Del Fosse and Church, 1981;Martínez-Pérez et al, 1999Prieto et al, 2004;Haizel et al, 2005;Tsubouchi and Roeder, 2005) and telomeres cluster to form the meiotic bouquet in most species (Bass et al, 2000;Niwa et al, 2000;Trelles-Sticken et al, 2000;Cowan et al, 2001;Scherthan, 2001;Harper et al, 2004). Both chromosomal structures are involved in interactions between different chromosomes and have been suggested to be participants in the election of the correct pairing partner.…”

“…Martínez-Pérez et al (2000) suggested that premeiotic centromere association is an effect induced by polyploidy since it appears in a wide range of cereal polyploids but not in their related diploids. However, premeiotic centromere association was also found in diploid species such as rye , rice (Prieto et al, 2004) or Luzula (Haizel et al, 2005).…”