Novel proteins required for meiotic silencing by unpaired DNA and siRNA generation in Neurospora crassa

Genetics. 2013 May;194(1):91-100. doi: 10.1534/genetics.112.148999. Epub 2013 Mar 15.

Abstract

During meiosis in the filamentous fungus Neurospora crassa, unpaired genes are identified and silenced by a process known as meiotic silencing by unpaired DNA (MSUD). Previous work has uncovered six proteins required for MSUD, all of which are also essential for meiotic progression. Additionally, they all localize in the perinuclear region, suggesting that it is a center of MSUD activity. Nevertheless, at least a subset of MSUD proteins must be present inside the nucleus, as unpaired DNA recognition undoubtedly takes place there. In this study, we identified and characterized two new proteins required for MSUD, namely SAD-4 and SAD-5. Both are previously uncharacterized proteins specific to Ascomycetes, with SAD-4 having a range that spans several fungal classes and SAD-5 seemingly restricted to a single order. Both genes appear to be predominantly expressed in the sexual phase, as molecular study combined with analysis of publicly available mRNA-seq datasets failed to detect significant expression of them in the vegetative tissue. SAD-4, like all known MSUD proteins, localizes in the perinuclear region of the meiotic cell. SAD-5, on the other hand, is found in the nucleus (as the first of its kind). Both proteins are unique compared to previously identified MSUD proteins in that neither is required for sexual sporulation. This homozygous-fertile phenotype uncouples MSUD from sexual development and allows us to demonstrate that both SAD-4 and SAD-5 are important for the production of masiRNAs, which are the small RNA molecules associated with meiotic silencing.

Publication types

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

MeSH terms

  • Cell Nucleus / metabolism
  • Crosses, Genetic
  • DNA, Fungal / metabolism*
  • Fungal Proteins / metabolism*
  • Gene Deletion
  • Gene Expression Regulation, Fungal
  • Gene Silencing*
  • Genes, Dominant / genetics
  • Genes, Fungal / genetics
  • Genes, Suppressor
  • Homozygote
  • Meiosis*
  • Neurospora crassa / cytology*
  • Neurospora crassa / genetics
  • Neurospora crassa / metabolism*
  • Phylogeny
  • RNA, Fungal / metabolism
  • RNA, Small Interfering / metabolism*
  • Reproduction / genetics

Substances

  • DNA, Fungal
  • Fungal Proteins
  • RNA, Fungal
  • RNA, Small Interfering