Kinetic characterization of the two phosphate uptake systems in the fungus Neurospora crassa

Burns, D.J.W.; Beever, Ross E.

doi:10.1128/jb.132.2.511-519.1977

Cited by 58 publications

(25 citation statements)

References 28 publications

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“…200,000 cpm/4mol) into the initial growth medium. Rodlets were prepared from the radioactive conidia in the standard manner, and the 32p present in the final preparation was determined by liquid scintillation spectrometry (7). Radioactive phospholipids were separated by two-dimensional thin-layer chromatography (3).…”

Section: Methodsmentioning

confidence: 99%

Purification and chemical characterization of the rodlet layer of Neurospora crassa conidia

Beever¹,

Redgwell²,

Dempsey³

1979

J Bacteriol

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The rodlet layer of Neurospora crassa macroconidia has been purified and chemically characterized. Sheets of rodlets were released from the conidial surface by vigorously shaking conidia in water. Conidia were removed by filtration and low-speed centrifugation, and the rodlets were recovered from the supernatant by high-speed centrifugation. The rodlet pellet comprised 1.9% of the initial dry weight. Chemical analysis was hampered by the insolubility of the rodlets. They were not solubilized by heating in various protein-denaturing buffers and were only partially dissolved by heating in 1 M NaOH at 100°C for 5 min. Nevertheless, they were found to be largely composed of protein (91%, based on total nitrogen). The major amino acids in acid hydrolysates were aspartic acid, glycine, serine, alanine, half-cystine, and valine. Glucosamine was not detected in acid hydrolysates. The sulfur content was 2.5%, and this could be accounted for in half-cystine and methionine. Carbohydrate comprised just over 2%. The phosphorus content was 0.21%, of which less than one-third was accounted for in phospholipid. The total fatty acid content was 1.0%, most of which could be accounted for by the fatty acids of the phospholipids. 1063 on August 2, 2020 by guest

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Section: Methodsmentioning

confidence: 99%

Purification and chemical characterization of the rodlet layer of Neurospora crassa conidia

Beever¹,

Redgwell²,

Dempsey³

1979

J Bacteriol

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“…Multiple mechanisms of transport are involved in acquisition of Pi and maintenance of cellular Pi homeostasis. Kinetic analysis has shown that Pi uptake occurs in a bi-phasic manner, and consists of high-affinity (K m 1-10 µM) and low-affinity (K m 100-1000 µM) uptake mechanisms in plants (Clarkson, 1984), bacteria (Rao & Torriani, 1990), yeast (Borst-Pauwels, 1981) and other fungi (Burns & Beever, 1977), including germ tubes of the mycorrhizal fungus, Gigaspora margarita (Thomson et al, 1990).…”

Section: mentioning

confidence: 99%

A Lycopersicon esculentum phosphate transporter (LePT1) involved in phosphorus uptake from a vesicular–arbuscular mycorrhizal fungus

et al. 1999

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In vesicular-arbuscular mycorrhizal symbioses, specialized fungal structures (the arbuscules) are formed which are in intimate contact with plant root cortical cells. It is assumed that these arbuscules are the major sites of solute transfer between the plant and fungus, but there have been no studies that definitively show the extent or types of transfer processes that occur in this structure. Phosphate is one of the major nutrients that is acquired by mycorrhizal fungi and transferred to plants. In this study a single Lycopersicon esculentum cDNA was cloned and shown to be identical to LePT1, a previously cloned inorganic-phosphate transporter. Expression studies revealed that LePT1 transcript levels remained constant in mycorrhizal plants, but increased in phosphate-starved, nonmycorrhizal plants. Localization of the LePT1 transcript by in situ hybridization showed that this gene is highly expressed in arbuscule-containing cortical cells in mycorrhizal plants. In non-mycorrhizal plants LePT1 expression was localized to the stele and cortex. The expression studies suggest that this transporter is involved in phosphate nutrition of L. esculentum and its localization in cells that contain arbuscules indicate that it may be the mechanism used by the plant to take up phosphate that is effluxed across the fungal plasma membrane of the arbuscule. Based on our findings and those of others, an integrated model of inorganic phosphate uptake and transfer in mycorrhizal and non-mycorrhizal plants is presented.Key words : mycorrhiza, transport, phosphate, tomato, in situ RNA localization, arbuscule. Inorganic phosphate (Pi) is required in relatively large amounts and is often a limiting nutrient for plant growth. The low concentration of Pi in the soil solution (1-10 µM) and its relative immobility leads to the formation of zones depleted in Pi around the actively absorbing roots. These depletion zones effectively limit Pi uptake in non-mycorrhizal plants. The symbiotic association formed between plants and vesicular-arbuscular (VA) mycorrhizal fungi allows plants to access Pi beyond the depletion zone

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“…Notwithstanding morphological and membrane changes, differential partitioning of nutrients within hyphae might also contribute to spatial differences in absorption along the hyphal length. Early work by Beever & Burns (1977) indicated that phosphorus absorption by N. crassa mycelia is regulated by the internal inorganic phosphate (PJ concentrations. Subsequent workers have confirmed that a similar regulation of phosphate transport occurs in mycelia of soil-borne basidiomycete saprotrophs (Clipson et al, 1987), AM (Thomson, Clarkson & Brain, 1990) and ECM fungi (Cairney & Smith, 1992).…”

Section: Nutrient Absorptionmentioning

confidence: 99%

“…Swenson, 1960) or rapidlygrowing germlings of filamentous fungi (e.g. Burns & Beever, 1977). It has therefore been suggested that modified conditions favouring efflux of phosphate from the fungus must exist in the apoplast of the fungus-root interface to stimulate rates of efflux sufficiently high to meet the demands of the host (Smith & Smith, 1989.…”

Section: Ectomycorrhizal Symbiosismentioning

confidence: 99%

Physiological heterogeneity within fungal mycelia: an important concept for a functional understanding of the ectomycorrhizal symbiosis

Cairney

Burke²

1996

New Phytologist

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SUMM.ARYIndividual mycelia of filamentous fungi display considerable heterogeneity at the physiological level. Important physiological processes such as nutrient absorption, extracellular enzyme secretion and solute translocation occur differentially within an individual mycelium, and vary according to spatio-temporal changes in patterns of gene expression as the mycelium develops and senesces. In ectomycorrhiza] (ECM) fungi, gene expression appears to be strongly influenced by interaction with the soil environment and the host root. The ECM mycelium is thus a complex and dynamic entity wherein discrete regions display particular physiological attributes. Physiological heterogeneity is important in the overall functioning of the symbiosis. In the particular case of movement of phosphorus from soil to host root in the ECM symbiosis, heterogeneity might provide the driving force for the integrated processes of absorption, translocation and transfer. It is suggested that it is only by considering the sum of the seemingly disparate physiological processes within the heterogeneous mycelium that mycorrhizal functioning can be fully understood.

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Kinetic characterization of the two phosphate uptake systems in the fungus Neurospora crassa

Cited by 58 publications

References 28 publications

Purification and chemical characterization of the rodlet layer of Neurospora crassa conidia

Purification and chemical characterization of the rodlet layer of Neurospora crassa conidia

A Lycopersicon esculentum phosphate transporter (LePT1) involved in phosphorus uptake from a vesicular–arbuscular mycorrhizal fungus

Physiological heterogeneity within fungal mycelia: an important concept for a functional understanding of the ectomycorrhizal symbiosis

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