The condensin complexes play distinct roles to ensure normal chromosome morphogenesis during meiotic division in Arabidopsis

Abstract

Meiosis is a specialized cell division essential for sexual reproduction. During meiosis the chromosomes are highly organized, and correct chromosome architecture is required for faithful segregation of chromosomes at anaphase I and II. Condensin is involved in chromosome organization during meiotic and mitotic cell divisions. Three condensin subunits, AtSMC4 and the condensin I and II specific subunits AtCAP-D2 and AtCAP-D3, respectively, have been studied for their role in meiosis. This has revealed that both the condensin I and condensin II complexes are required to maintain normal structural integrity of the meiotic chromosomes during the two nuclear divisions. Their roles appear functionally distinct in that condensin I is required to maintain normal compaction of the centromeric repeats and 45S rDNA, whereas loss of condensin II was associated with extensive interchromosome connections at metaphase I. Depletion of condensin is also associated with a slight reduction in crossover formation, suggesting a role during meiotic prophase I.

The PHD Finger Protein MMD1/DUET Ensures the Progression of Male Meiotic Chromosome Condensation and Directly Regulates the Expression of the Condensin Gene CAP-D3

“…Consistent with the RNA-seq data, the expression of several condensin genes (CAP-D2, CAP-D3, CAP-H, and CAP-H2) was significantly reduced in mmd1 meiocytes compared with the wild type ( Figure 7B), with CAP-D3 showing the greatest reduction ( Figure 7B). In previous studies, Arabidopsis CAP-D3 was localized to chromatin in mitotic cells (Schubert et al, 2013;Smith et al, 2014). We therefore performed immunofluorescence experiments in meiocytes and found that the level of CAP-D3 protein was significantly lower in mmd1 chromosomes than in the wild type (Figure 8), providing additional evidence that supports a role for MMD1 in regulating meiotic condensation, in part by affecting CAP-D3 expression levels.…”

“…Previous studies in Arabidopsis showed that condensin proteins have a role in the frequency of meiotic recombination (Smith et al, 2014). We thus examined the recombination frequency in the wild type and mmd1 by counting the chiasmata number at diplotene (Figure 4).…”

“…SMC2 and SMC4 are essential genes, and corresponding mutants in Arabidopsis thaliana, yeast, Drosophila melanogaster, and Caenorhabditis elegans are lethal (Hirano, 2012). In addition, genetic studies using conditional alleles, tissuespecific disruption, and RNAi targeting condensin genes show that they are also important for mitotic and meiotic chromosome condensation and/or segregation in C. elegans (Hagstrom et al, 2002;Chan et al, 2004), D. melanogaster (Hartl et al, 2008), yeast (Yu and Koshland, 2003), and Arabidopsis (Siddiqui et al, 2003;Schubert et al, 2013;Smith et al, 2014).…”

“…Furthermore, the relative ratio of condensin I and II affects metaphase chromosome conformation (Shintomi and Hirano, 2011). Moreover, genes encoding condensin II subunits, such as CAP-D3, have been implicated in meiosis (Lee et al, 2011;Hirano, 2012;Smith et al, 2014). In yeast (Saccharomyces cerevisiae), condensin plays a role in the association of other meiotic chromosome components, to promote SC assembly and facilitate chromosome segregation (Yu and Koshland, 2003;Yu and Koshland, 2005).…”

MS5 Mediates Early Meiotic Progression and Its Natural Variants May Have Applications for Hybrid Production in Brassica napus

“…Mutations in condensin genes lead to major developmental defects in plants (Liu et al, 2002;Siddiqui et al, 2003;Siddiqui et al, 2006). Although the biological function of condensin in plant meiosis remains elusive, recent studies in Arabidopsis have revealed its role in maintaining normal meiotic chromosome integrity (Schubert et al, 2013;Smith et al, 2014). Chromosome structure and higher-order configuration appear to be closely related to cell cycle progression during meiosis.…”