Impairment of calcineurin function in Neurospora crassa reveals its essential role in hyphal growth, morphology and maintenance of the apical Ca2+ gradient

Mol Gen Genet. 1997 Sep;256(2):104-14. doi: 10.1007/s004380050551.

Abstract

The function of Neurospora crassa calcineurin was investigated in N. crassa strains transformed with a construct that provides for the inducible expression of antisense RNA for the catalytic subunit of calcineurin (cna-1). Induction of antisense RNA expression was associated with reduced levels of cna-1 mRNA and of immunodetectable CNA1 protein and decreased calcineurin enzyme activity, indicating that a conditional reduction of the target function had been achieved in antisense transformants with multiple construct integrations. Induction conditions caused growth arrest which indicated that the cna-1 gene is essential for growth of N. crassa. Growth arrest was preceded by an increase in hyphal branching, changes in hyphal morphology and concomitant loss of the distinctive tip-high Ca2+ gradient typical for growing wild-type hyphae. This demonstrates a novel and specific role for calcineurin in the precise regulation of apical growth, a common form of cellular proliferation. In vitro inhibition of N. crassa calcineurin by the complex of cyclosporin A (CsA) and cyclophilin20, and increased sensitivity of the induced transformants to the calcineurin-specific drugs CsA and FK506 imply that the drugs act in N. crassa, as in T-cells and Saccharomyces cerevisiae, by inactivating calcineurin. The finding that exposure of growing wild-type mycelium to these drugs leads to a phenotype very similar to that of the cna-1 antisense mutants is consistent with this idea.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calcineurin / genetics
  • Calcineurin / metabolism
  • Calcineurin / physiology*
  • Calcium / metabolism
  • Cloning, Molecular
  • Cyclosporine / pharmacology
  • Gene Expression Regulation, Enzymologic
  • Gene Expression Regulation, Fungal
  • Immunosuppressive Agents / pharmacology
  • Neurospora crassa / enzymology
  • Neurospora crassa / genetics*
  • Neurospora crassa / growth & development*
  • Peptidylprolyl Isomerase / pharmacology
  • Plasmids
  • RNA, Antisense / genetics
  • RNA, Messenger / metabolism
  • Recombination, Genetic
  • Tacrolimus / pharmacology
  • Transcription, Genetic
  • Transformation, Genetic

Substances

  • Immunosuppressive Agents
  • RNA, Antisense
  • RNA, Messenger
  • Cyclosporine
  • Calcineurin
  • Peptidylprolyl Isomerase
  • Calcium
  • Tacrolimus