The Structure-Specific Endonucleases MUS81 and SEND1 Are Essential for Telomere Stability in Arabidopsis

Plant Cell. 2016 Jan;28(1):74-86. doi: 10.1105/tpc.15.00898. Epub 2015 Dec 24.


Structure-specific endonucleases act to repair potentially toxic structures produced by recombination and DNA replication, ensuring proper segregation of the genetic material to daughter cells during mitosis and meiosis. Arabidopsis thaliana has two putative homologs of the resolvase (structure-specific endonuclease): GEN1/Yen1. Knockout of resolvase genes GEN1 and SEND1, individually or together, has no detectable effect on growth, fertility, or sensitivity to DNA damage. However, combined absence of the endonucleases MUS81 and SEND1 results in severe developmental defects, spontaneous cell death, and genome instability. A similar effect is not seen in mus81 gen1 plants, which develop normally and are fertile. Absence of RAD51 does not rescue mus81 send1, pointing to roles of these proteins in DNA replication rather than DNA break repair. The enrichment of S-phase histone γ-H2AX foci and a striking loss of telomeric DNA in mus81 send1 further support this interpretation. SEND1 has at most a minor role in resolution of the Holliday junction but acts as an essential backup to MUS81 for resolution of toxic replication structures to ensure genome stability and to maintain telomere integrity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / cytology
  • Arabidopsis / growth & development
  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / metabolism*
  • Cell Cycle
  • Chromosomes, Plant / genetics
  • DNA Repair
  • DNA Replication
  • DNA, Bacterial / genetics
  • Endonucleases / metabolism*
  • Genomic Instability
  • Holliday Junction Resolvases / metabolism*
  • Meiosis
  • Mutagenesis, Insertional / genetics
  • Mutation / genetics
  • Phenotype
  • Rad51 Recombinase / metabolism
  • Telomere / metabolism*


  • Arabidopsis Proteins
  • DNA, Bacterial
  • T-DNA
  • ATRAD51 protein, Arabidopsis
  • Rad51 Recombinase
  • Endonucleases
  • MUS81 protein, Arabidopsis
  • Holliday Junction Resolvases
  • SEND1 protein, Arabidopsis