SepB: An Aspergillus nidulans gene involved in chromosome segregation and the initiation of cytokinesis

Steven D. Harris, John E. Hamer

Research output: Contribution to journalArticlepeer-review

39 Scopus citations


In Aspergillus nidulans conidia, cytokinesis (septation) is delayed until three rounds of nuclear division have been completed. This has permitted the identification of essential genes that are involved in the coordination of cytokinesis with nuclear division. Conditional mutations in the sepB gene block septation but allow germinating spores to complete the first three rounds of nuclear division at restrictive temperature. sepB3 mutants demonstrate transient delays in M-phase, accumulate aneuploid nuclei and show defects in chromosome segregation. Molecular analysis of the sepB gene reveals that it is essential and possesses limited similarity to the CTF4 gene of Saccharomyces cerevisiae. Using temperature-shift analysis we show that sepB is required after the first nuclear division but before the onset of cytokinesis. A failure to execute the sepB function results in a block to nuclear division and leads to cell death at a time when wild-type cells would be undergoing cytokinesis. Finally, we demonstrate that sepB is also required for the uninucleate cell divisions of developing conidiophores. Our results suggest that sepB3 mutants accumulate specific nuclear defects that do not arrest mitosis, but block the initiation of septum formation. Thus, proper chromosome segregation and a functional sepB gene are required to initiate cytokinesis.

Original languageEnglish (US)
Pages (from-to)5244-5247
Number of pages4
JournalEMBO Journal
Issue number21
StatePublished - 1995
Externally publishedYes


  • Aspergillus
  • Cell cycle
  • Cytokinesis
  • Nuclear division
  • Septation

ASJC Scopus subject areas

  • General Neuroscience
  • Molecular Biology
  • General Biochemistry, Genetics and Molecular Biology
  • General Immunology and Microbiology


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