Ca(2+) shuttling in vesicles during tip growth in Neurospora crassa

Fungal Genet Biol. 2001 Aug;33(3):181-93. doi: 10.1006/fgbi.2001.1282.

Abstract

Tip-growing organisms maintain an apparently essential tip-high gradient of cytoplasmic Ca(2+). In the oomycete Saprolegnia ferax, in pollen tubes and root hairs, the gradient is produced by a tip-localized Ca(2+) influx from the external medium. Such a gradient is normally dispensable for Neurospora crassa hyphae, which may maintain their Ca(2+) gradient by some form of internal recycling. We localized Ca(2+) in N. crassa hyphae at the ultrastructural level using two techniques (a) electron spectroscopic imaging of freeze-dried hyphae and (b) pyroantimoniate precipitation. The results of both methods support the presence of Ca(2+) in the wall vesicles and Golgi body equivalents, providing a plausible mechanism for the generation and maintenance of the gradient by Ca(2+) shuttling in vesicles to the apex, without exogenous Ca(2+) influx. Ca(2+) sequestration into the vesicles seems to be dependent on Ca(2+)-ATPases since cyclopiazonic acid, a specific inhibitor of Ca(2+) pumps, eliminated all Ca(2+) deposits from the vesicles of N. crassa.

MeSH terms

  • Antimony / chemistry
  • Calcium / metabolism*
  • Chemical Precipitation
  • Electron Probe Microanalysis
  • Freeze Drying
  • Golgi Apparatus / metabolism
  • Golgi Apparatus / ultrastructure
  • Microscopy, Electron / instrumentation
  • Microscopy, Electron / methods
  • Neurospora crassa / growth & development*
  • Neurospora crassa / metabolism*
  • Neurospora crassa / ultrastructure
  • Organelles / metabolism*
  • Organelles / ultrastructure

Substances

  • pyroantimonate
  • Antimony
  • Calcium