Meiotic Chromosome Structure and Function in Plants

Abstract

Chromosome structure is important for many meiotic processes. Here, we outline 3 main determinants of chromosome structure and their effects on meiotic processes in plants. Cohesins are necessary to hold sister chromatids together until the first meiotic division, ensuring that homologous chromosomes and not sister chromatids separate during anaphase I. During meiosis in maize, Arabidopsis, and rice, cohesins are needed for establishing early prophase chromosome structure and recombination and for aligning bivalents at the metaphase plate. Condensin complexes play pivotal roles in controlling the packaging of chromatin into chromosomes through chromatin compaction and chromosome individualization. In animals and fungi, these complexes establish a meiotic chromosome structure that allows for proper recombination, pairing, and synapsis of homologous chromosomes. In plants, information on the role of condensins in meiosis is limited, but they are known to be required for successful completion of reproductive development. Therefore, we speculate that they play roles similar to animal and fungal condensins during meiosis. Plants generally have large and complex genomes due to frequent polyploidy events, and likely, condensins and cohesins organize chromosomes in such a way as to ensure genome stability. Hexaploid wheat has evolved a unique mechanism using a Ph1 locus-controlled chromosome organization to ensure proper chromosome pairing in meiosis. Altogether, studies on meiotic chromosome structure indicate that chromosome organization is not only important for chromatin packaging but also fulfills specific functions in facilitating chromosome interactions during meiosis, including pairing and recombination.

Chromatin dynamics during cellular differentiation in the female reproductive lineage of flowering plants

“…This very specific phase of chromatin dynamics has been nicely reviewed elsewhere (e.g. Pawlowski, 2010 ; Mainiero and Pawlowski, 2014 ).…”

Repetitive DNA in the Architecture, Repatterning, and Diversification of the Genome of Aegilops speltoides Tausch (Poaceae, Triticeae)

“…Presumably, an artificial asymmetry in tandem repeat patterns in the F1 intraspecific plant(s) could negatively affect the hybrid genomes’ stability, specifically, by altering the chromosome pairing and segregation. In addition, the subtelomeric location of Spelt1 may be tightly connected with telomere functioning and dynamics during both mitosis and meiosis (Bozza and Pawlowski, 2008; Tiang et al, 2012; Mainiero and Pawlowski, 2014). In the early meiotic prophase, homolog pairing is accompanied by repositioning of chromosomes in the nuclear space and “telomere bouquet” formation; and clustering of telomeres on the nuclear envelope may continue until early pachytene.…”

The Cohesin Complex Subunit ZmSMC3 Participates in Meiotic Centromere Pairing in Maize

“…The cohesin complex has been reported to facilitate chromosome pairing during meiosis in addition to sister-chromatids cohesion (Nasmyth, 2011). This ring-shaped structure plays an important role in determining chromosome morphology (Mainiero and Pawlowski, 2014). The cohesin complex consists of a core cohesin ring and several associated proteins.…”