Accurate Chromosome Segregation at First Meiotic Division Requires AGO4, a Protein Involved in RNA-Dependent DNA Methylation in Arabidopsis thaliana

Genetics. 2016 Oct;204(2):543-553. doi: 10.1534/genetics.116.189217. Epub 2016 Jul 27.

Abstract

The RNA-directed DNA methylation (RdDM) pathway is important for the transcriptional repression of transposable elements and for heterochromatin formation. Small RNAs are key players in this process by regulating both DNA and histone methylation. Taking into account that methylation underlies gene silencing and that there are genes with meiosis-specific expression profiles, we have wondered whether genes involved in RdDM could play a role during this specialized cell division. To address this issue, we have characterized meiosis progression in pollen mother cells from Arabidopsis thaliana mutant plants defective for several proteins related to RdDM. The most relevant results were obtained for ago4-1 In this mutant, meiocytes display a slight reduction in chiasma frequency, alterations in chromatin conformation around centromeric regions, lagging chromosomes at anaphase I, and defects in spindle organization. These abnormalities lead to the formation of polyads instead of tetrads at the end of meiosis, and might be responsible for the fertility defects observed in this mutant. Findings reported here highlight an involvement of AGO4 during meiosis by ensuring accurate chromosome segregation at anaphase I.

Keywords: AGO4; Arabidopsis thaliana; RdDM; centromere; meiosis.

MeSH terms

  • Anaphase / genetics
  • Arabidopsis / genetics*
  • Arabidopsis Proteins / genetics*
  • Argonaute Proteins / genetics*
  • Centromere / genetics
  • Chromatin Assembly and Disassembly / genetics
  • Chromosome Segregation / genetics
  • Chromosomes, Plant / genetics
  • DNA Methylation / genetics*
  • Gene Expression Regulation, Plant
  • Meiosis / genetics*
  • Pollen / genetics
  • Pollen / growth & development
  • RNA, Plant / genetics

Substances

  • AGO4 protein, Arabidopsis
  • Arabidopsis Proteins
  • Argonaute Proteins
  • RNA, Plant