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A cytosine methyltransferase homologue is essential for sexual development in Aspergillus nidulans

Dong W Lee1, Michael Freitag, Eric U Selker

  • 1Department of Biology, College of Science, Texas A&M University, College Station, Texas, United States of America.

Plos One
|June 26, 2008
PubMed
Abstract

Insights

A novel DNA methyltransferase homologue (dmtA) in Aspergillus nidulans is crucial for sexual development, despite the fungus lacking known DNA methylation and genome defense systems like RIP or MIP. This suggests a new function for DNA methyltransferase domains in fungal development.

Area of Science:

  • Mycology
  • Genetics
  • Molecular Biology

Background:

  • Repeat-induced point mutation (RIP) and methylation induced premeiotically (MIP) are genome defense systems in fungi.
  • These systems rely on proteins with DNA methyltransferase (DMT) domains, such as RID and Masc1.
  • A homologue was identified in Aspergillus nidulans, a species not known to possess these systems or DNA methylation.

Purpose of the Study:

  • To clone and characterize the DNA methyltransferase homologue A (dmtA) gene in Aspergillus nidulans.
  • To investigate the function of dmtA and its associated transcript tmdA in fungal development.
  • To determine if DNA methylation occurs in Aspergillus nidulans and its relation to dmtA.

Main Methods:

  • Gene cloning and characterization of dmtA and tmdA in Aspergillus nidulans.
  • Analysis of transcript expression in vegetative, conidial, and sexual tissues.
  • Construction and analysis of dmtA/tmdA mutants to assess developmental roles and DNA methylation levels.

Main Results:

  • The dmtA locus produces both sense (dmtA) and anti-sense (tmdA) transcripts, expressed in all tested tissues.
  • dmtA, but not tmdA, is essential for early sexual development and the formation of viable ascospores.
  • Constructed dmtA/tmdA mutants showed no detectable DNA methylation, similar to wild-type strains.

Conclusions:

  • A DMT homologue (DmtA) has an essential developmental role in Aspergillus nidulans, a fungus lacking detectable DNA methylation and RIP/MIP.
  • While DmtA might be involved in undetected, trace DNA methylation, its primary function appears distinct from canonical DNA methylation.
  • The DMT domain in the RID/Masc1/DmtA family may possess a previously unrecognized function in fungal development.

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