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A cytoplasmic lectin produced by the fungus Arthrobotrys oligospora functions as a storage protein during saprophytic and parasitic growth

Author:
  • Stefan Rosén
  • Klaas Sjollema
  • Marten Veenhuis
  • Anders Tunlid
Publishing year: 1997-01-01
Language: English
Pages: 2593-2604
Publication/Series: Microbiology
Volume: 143
Issue: 8
Document type: Journal article
Publisher: MAIK Nauka/Interperiodica

Abstract english

It was recently shown that the nematode-infecting fungus Arthrobotrys oligospora contains a saline-soluble lectin (designated AOL) that is a member of a novel family of fungal lectins sharing similar primary sequences and binding specificities. During saprophytic growth in liquid cultures, levels of AOL and AOL mRNA were found to vary depending on the growth phase of the mycelium and the carbon/nitrogen (C/N) ratio of the medium. AOL was not detected in young mycelium. In older mycelium (stationary growth phase) grown in media with low UN ratios (1 or 6), AOL comprised 5-20% of the total amount of saline-soluble proteins present in the mycelium. Neither the lectin nor its transcript was detected in mycelia grown in medium with higher C/N ratios (≤ 150). Under conditions of nitrogen starvation, AOL was preferentially degraded in relation to the total amount of saline-soluble proteins present in the mycelium. During the infection of nematodes, the level of AOL protein and AOL mRNA increased significantly once the nematodes had been penetrated and digested. Large amounts of AOL accumulated in the trophic hyphae growing inside the nematode as visualized by immunofluorescence microscopy. Later, AOL labelling was detected outside the digested nematodes, preferentially in strands of aggregated hyphae and in newly developed trap cells. Electron microscopy showed that AOL was localized to the cytoplasm and the nucleus-of both vegetative mycelium and trap cells, and in the trophic hyphae growing inside the infected nematodes. These results indicate that AOL functions as a storage protein during both saprophytic and parasitic growth.

Keywords

  • Microbiology
  • Immunolocalization
  • Lectin
  • Nematophagous fungus
  • Storage protein

Other

Published
  • ISSN: 1350-0872
Anders Tunlid
E-mail: anders [dot] tunlid [at] biol [dot] lu [dot] se

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