TONSOKU is expressed in S phase of the cell cycle and its defect delays cell cycle progression in Arabidopsis

Plant Cell Physiol. 2005 May;46(5):736-42. doi: 10.1093/pcp/pci082. Epub 2005 Mar 3.


TONSOKU(TSK)/MGOUN3/BRUSHY1 of Arabidopsis thaliana encodes a nuclear leucine-glycine-aspargine (LGN) domain protein implicated to be involved in genome maintenance, and mutants with defects in TSK show a fasciated stem with disorganized meristem structures. We identified a homolog of TSK from tobacco BY-2 cells (NtTSK), which showed high sequence conservation both in the LGN domain and in leucine-rich repeats with AtTSK. The NtTSK gene was expressed during S phase of the cell cycle in tobacco BY-2 cells highly synchronized for cell division. The tsk mutants of Arabidopsis contained an increased proportion of cells with 4C nuclei and cells expressing cyclin B1 compared with the wild type. These results suggest that TSK is required during the cell cycle and defects of TSK cause the arrest of cell cycle progression at G2/M phase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Arabidopsis / genetics
  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism*
  • Cell Nucleus / genetics
  • Cell Nucleus / metabolism
  • Cloning, Molecular
  • Cyclin B / genetics
  • Cyclin B / metabolism
  • G2 Phase / genetics
  • Genes, cdc / physiology*
  • Molecular Sequence Data
  • Mutation / genetics
  • Plant Proteins / genetics
  • Plant Proteins / metabolism
  • S Phase / genetics*
  • Sequence Homology, Amino Acid
  • Tobacco / genetics
  • Tobacco / metabolism


  • Arabidopsis Proteins
  • Cell Cycle Proteins
  • CycB1 protein, Arabidopsis
  • Cyclin B
  • MGOUN3 protein, Arabidopsis
  • Plant Proteins