A single argonaute gene participates in exogenous and endogenous RNAi and controls cellular functions in the basal fungus Mucor circinelloides

PLoS One. 2013 Jul 23;8(7):e69283. doi: 10.1371/journal.pone.0069283. Print 2013.


The mechanism of RNAi is well described in metazoans where it plays a role in diverse cellular functions. However, although different classes of endogenous small RNAs (esRNAs) have been identified in fungi, their biological roles are poorly described due, in part, to the lack of phenotype of mutants affected in the biogenesis of these esRNAs. Argonaute proteins are one of the key components of the RNAi pathways, in which different members of this protein family participate in the biogenesis of a wide repertoire of esRNAs molecules. Here we identified three argonaute genes of the fungus Mucor circinelloides and investigated their participation in exogenous and endogenous RNAi. We found that only one of the ago genes, ago-1, is involved in RNAi during vegetative growth and is required for both transgene-induced RNA silencing and the accumulation of distinct classes of esRNAs derived from exons (ex-siRNAs). Classes I and II ex-siRNAs bind to Ago-1 to control mRNA accumulation of the target protein coding genes. Class III ex-siRNAs do not specifically bind to Ago-1, but requires this protein for their production, revealing the complexity of the biogenesis pathways of ex-siRNAs. We also show that ago-1 is involved in the response to environmental signals, since vegetative development and autolysis induced by nutritional stress are affected in ago-1(-) M. circinelloides mutants. Our results demonstrate that a single Ago protein participates in the production of different classes of esRNAs that are generated through different pathways. They also highlight the role of ex-siRNAs in the regulation of endogenous genes in fungi and expand the range of biological functions modulated by RNAi.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Argonaute Proteins / chemistry
  • Argonaute Proteins / genetics*
  • Argonaute Proteins / metabolism
  • Autolysis
  • Gene Expression Regulation, Fungal
  • Gene Knockout Techniques
  • Genes, Fungal / genetics*
  • Molecular Sequence Data
  • Mucor / cytology*
  • Mucor / genetics*
  • Mutation / genetics
  • Protein Binding
  • Protein Structure, Tertiary
  • RNA Interference*
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • RNA, Small Interfering / metabolism
  • Reproduction, Asexual / genetics
  • Spores, Fungal / physiology
  • Transgenes / genetics


  • Argonaute Proteins
  • RNA, Messenger
  • RNA, Small Interfering

Grant support

This work was supported by the Spanish Ministerio de Ciencia e Innovación (BFU2006-02408 and BFU2009-07220, co-financed by FEDER); and the Spanish Ministerio de Economía y Competitividad (BFU2012-32246). F.E.N. was funded by the U-IMPACT Program (Marie Curie Action, 7th Framework Programme of the EU) within the Regional Campus of International Excellence “Campus Mare Nostrum” (Murcia, Spain). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.