Vacuoles Play a Decisive Role in Calcium Homeostasis in Neurospora crassa

Cornelius, G.; Nakashima, Hiroaki

doi:10.1099/00221287-133-8-2341

Cited by 31 publications

(41 citation statements)

References 30 publications

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“…crassa as in other eukaryotic organisms, probably participate in multiple regulatory functions, some of which require the hyphae to maintain a low level of free cytosolic Ca2+. The recent report that mutants defective in the transport of Ca2+ into a vacuolar fraction are subject to inhibition by extracellular Ca2+ (Cornelius & Nakashima, 1987) supports this presumption. It seems likely, then, that CTC fluorescence mainly reports the distribution of membrane-bound compartments that sequester the bulk of the Ca2+ complement of the hyphae.…”

Section: Discussionsupporting

confidence: 60%

Dual Roles for Calcium Ions in Apical Growth of Neurospora crassa

Schmid

Harold

1988

Microbiology

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We report initial attempts to define the role of Ca2+ in the polarized extension of Neurospora crassa. Growth of the organism was diminished in media containing less than 1 mM-Ca2+; extension was more severely impaired than biomass synthesis, resulting in the formation of stubby, bulbous hyphae, even of spherical cells. Reduced extension and abnormal morphology were correlated with the loss of surface-bound Ca2+, probably associated with the cell wall. Intracellular Ca2+ may be represented by material that fluoresces brightly in the presence of chlortetracycline. Punctate fluorescent bodies and diffuse fluorescence were both arrayed in a longitudinal gradient, maximum apically. Addition of the calcium ionophore A23 187 induced dissipation of the fluorescence; concurrently, the hyphae lost as much as one half of their Ca2+ content. Extension continued almost unabated, but multiple branches quickly emerged from the apex. The observations suggest that a cytoplasmic Ca2+ gradient is not required for polarized extension, but may play a role in ensuring the dominance of the apex.

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Section: Discussionsupporting

confidence: 60%

Dual Roles for Calcium Ions in Apical Growth of Neurospora crassa

Schmid

Harold

1988

Microbiology

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“…The ability of the mitochondria and vacuoles to sequester Ca2+ suggests that these organelles, which are particularly large and abundant in appressoria (Zacharuk, 1970 ;Goettel et al, 1989) may function to maintain localized cytoplasmic Ca2+ at the levels required for alterations in the cytoskeleton and other growth processes, as reported in plant systems (Picton & Steer, 1985). Consistent with this, mutants of Neurospora crassa defective in the transport of Ca2+ into a vacuolar fraction are subject to inhibition by extracellular Ca2+ (Cornelius & Nakashima, 1987). The sensitivity of Ca2+ uptake by Metarhizium vacuoles to ATP, Mg2+ and DCCD resembles reports for yeast vacuoles in which the driving force for uptake is a pH gradient produced by a H+-translocating ATPase that uses MgATP as a substrate (Uchida et al, 1988).…”

Section: Discussionsupporting

confidence: 62%

“…Immediately thereafter the fractions were assayed for protein content (Bradford, 1976) and for Ca2+ transport activity. Cornelius & Nakashima (1987) and Uchida et al (1988).] 45Ca2+ uptake by membrane fractions was measured at 22°C as follows.…”

Section: Methodsmentioning

confidence: 99%

Second messenger involvement in differentiation of the entomopathogenic fungus Metarhizium anisopliae

Leger

Butt

Staples

et al. 1990

Journal of General Microbiology

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The conidial germling of Metarhizium anisopliue produces an appressorium upon contact with a hard hydrophobic surface. We have conducted an investigation into how this entomopathogen mediates intracellularly the inductive signal to shift from polarized germ-tube growth to non-polarized appressorial growth. During sporulation, conidia accumulated 45Ca2+ but there was no evidence for a gradient of Ca2+ in the spore which could establish the initial polarity. Calmodulin, however, was localized at the poles of the conidia, near the site of germ-tube emergence. Exposing conidia to Ca2+ deprivation or calmodulin antagonists inhibited germination and polar growth. Disruption of Ca2+ gradients by ionophoresis did not prevent germination but caused the multiple emergence of branched germ-tubes from conidia. These findings indicate that Ca2+ plays a fundamental role in establishing the dominance of apical growth. Although an external source of Ca2+ is not required for appressorium formation, germlings producing appressoria took up 45Ca2+ when available. The 45Ca2+ accumulated in the cell wall, plasma membrane and organelles suggesting that these may function as Ca2+ stores for Ca2+-stimulated exocytosis of cellwall materials. Mitochondria and vacuoles sequestered 45Ca2+ indicating that they play a role in maintaining low cytoplasmic concentrations of 45Ca2+ consistent with the reorganization of the cytoskeleton required for appressorial growth. Several Ca2+-binding proteins in appressoria may provide an energy-independent component of Ca2+ buffering in the cytoplasm. The results indicate that the apical Ca2+ gradient is disrupted during differentiation and subsequent differential Ca2+ redistribution in the cell enlargement zone coincides with germtube swelling. cAMP may also be involved by potentiating the effects of small changes in Ca2+ concentration and stimulating exocytosis of mucus components required for adhesion, which is a prerequisite for differentiation.

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“…Localization of metal ions in the vacuole enables low cytosolic concentrations of, for example, Ca^"^, to be maintained Eilam et al, 1985a, 6;Okorokov et al, 1985;Eilam & Chernichovsky, 1987;Cornelius & Nakashima, 1987;Ohsumi et al, 1988). Cytosolic concentrations of Mg^^ and Mn^^ may remain relatively constant, even under considerable environmental perturbations (Lichko et al, 1982;Kihn, Dassargues & Mestdagh, 1988).…”

Section: Intracellular Fate Of Toxic Metals* (A) Metal-binding Proteimentioning

confidence: 99%

Interactions of fungi with toxic metals

1993

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SUMMARY This review details the major interactions of fungi with toxic metal species. Physico‐chemical and biological aspects are discussed including definitions and classification of metals in biological contexts, mechanisms of metal fungitoxicity, resistance and tolerance, environmental influences and the occurrence of fungi in metal‐polluted habitats. Cellular interactions include extracellular precipitation and complexation, binding to cell walls, transport of monovalent and divalent metal cations, intracellular fates of toxic metal species (including metal‐binding proteins and peptides, and vacuolar compartmentation), and metal transformations including organometal(loid) synthesis. Significant interactions between metals and mycorrhizal fungi and macrofungi are summarized with reference to the amelioration of plant phytotoxicity and metal accumulation respectively. Biotechnological aspects of metal‐fungal interactions relate to the biological treatment of metal‐contaminated effluents and waste streams for metal removal/recovery and environmental protection.

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Vacuoles Play a Decisive Role in Calcium Homeostasis in Neurospora crassa

Cited by 31 publications

References 30 publications

Dual Roles for Calcium Ions in Apical Growth of Neurospora crassa

Dual Roles for Calcium Ions in Apical Growth of Neurospora crassa

Second messenger involvement in differentiation of the entomopathogenic fungus Metarhizium anisopliae

Interactions of fungi with toxic metals

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