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

H. Prokisch, O. Yarden, M. Dieminger, M. Tropschug, I. B. Barthelmess*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

113 Scopus citations

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.

Original languageAmerican English
Pages (from-to)104-114
Number of pages11
JournalMolecular and General Genetics
Volume256
Issue number2
DOIs
StatePublished - 1997

Bibliographical note

Funding Information:
Acknowledgements We thank R. Kincaid for the calcineurin cDNA, M. Plamann for the actin cDNA and V. Dombradi for providing O. Y. with the opportunity to perform the radioactive phosphatase assay in his lab. This work was supported, in part, by grants from the Volkswagen Foundation and the Ministry of Science of Lower Saxony (Collaborative projects between The Hebrew University of Jerusalem and universities in Lower Saxony, to O. Y. and I. B. B.), BARD (United States-Israel Binational Agricultural Research and Development Fund, to O. Y.), the Deutsche Forschungs gemeinschaft (SFB 388, to M. T.) and the Fond der Chemischen Industrie (to M. T.).

Keywords

  • Apical Ca gradient
  • Calcineurin
  • Cyclosporin A
  • FK506
  • Neurospora crassa

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