Immunocytochemical Localization of Phytotoxins inBipolaris sorokiniana

Åkesson, Helena; Carlemalm, Eric; Everitt, Einar; Gunnarsson, Torsten; Odham, Göran; Jansson, Hans

doi:10.1006/fgbi.1996.0036

Cited by 12 publications

(2 citation statements)

References 28 publications

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“…(iii) The intermediates stimulate a feedback repression system downregulating activities of one or both enzymes. Nevertheless, it was clear that CS10 could convert either sterigmatocystin or O-methylsterigmatocystin to aflatoxin B 1 , while LW1432 and LW1418 could convert Omethylsterigmatocystin to aflatoxin B 1 but were unable to convert sterigmatocystin to either O-methylsterigmatocystin or aflatoxin B 1 . These data clearly demonstrate that OmtA is necessary for efficient conversion of sterigmatocystin to Omethylsterigmatocystin in vivo in A. parasiticus CS10 under the specified growth and assay conditions.…”

Section: Discussionmentioning

confidence: 99%

Function of Native OmtA In Vivo and Expression and Distribution of This Protein in Colonies of Aspergillus parasiticus

Lee¹,

Chiou²,

Linz

2002

Appl Environ Microbiol

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The activities of two enzymes, a 168-kDa protein and a 40-kDa protein, OmtA, purified from the filamentous fungus Aspergillus parasiticus were reported to convert the aflatoxin pathway intermediate sterigmatocystin to O-methylsterigmatocystin in vitro. Our initial goal was to determine if OmtA is necessary and sufficient to catalyze this reaction in vivo and if this reaction is necessary for aflatoxin synthesis. We generated A. parasiticus omtA-null mutant LW1432 and a maltose binding protein-OmtA fusion protein expressed in Escherichia coli. Enzyme activity analysis of OmtA fusion protein in vitro confirmed the reported catalytic function of OmtA. Feeding studies conducted with LW1432 demonstrated a critical role for OmtA, and the reaction catalyzed by this enzyme in aflatoxin synthesis in vivo. Because of a close regulatory link between aflatoxin synthesis and asexual sporulation (conidiation), we hypothesized a spatial and temporal association between OmtA expression and conidiospore development. We developed a novel time-dependent colony fractionation protocol to analyze the accumulation and distribution of OmtA in fungal colonies grown on a solid medium that supports both toxin synthesis and conidiation. OmtA-specific polyclonal antibodies were purified by affinity chromatography using an LW1432 protein extract. OmtA was not detected in 24-h-old colonies but was detected in 48-h-old colonies using Western blot analysis; the protein accumulated in all fractions of a 72-h-old colony, including cells (0 to 24 h) in which little conidiophore development was observed. OmtA in older fractions of the colony (24 to 72 h) was partly degraded. Fluorescence-based immunohistochemical analysis conducted on thin sections of paraffin-embedded fungal cells from time-fractionated fungal colonies demonstrated that OmtA is evenly distributed among different cell types and is not concentrated in conidiophores. These data suggest that OmtA is present in newly formed fungal tissue and then is proteolytically cleaved as cells in that section of the colony age.

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Section: Discussionmentioning

confidence: 99%

Function of Native OmtA In Vivo and Expression and Distribution of This Protein in Colonies of Aspergillus parasiticus

Lee¹,

Chiou²,

Linz

2002

Appl Environ Microbiol

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“…Major labelling was seen in membrane‐bound organelles identified as Woronin bodies. These spherical, hexagonal, or rectangular proteinaceous crystals plug the septal pores, thereby distinguishing old damaged fungal hyphae from the rest of the mycelium (Akesson et al ., 1996).…”

Section: Disease Resistance and Controlmentioning

confidence: 99%

Bipolaris sorokiniana, a cereal pathogen of global concern: cytological and molecular approaches towards better control‡

Kumar

Schäfer

Hückelhoven

et al. 2002

Molecular Plant Pathology

305

221

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Summary Bipolaris sorokiniana (teleomorph Cochliobolus sativus ) is the causal agent of common root rot, leaf spot disease, seedling blight, head blight, and black point of wheat and barley. The fungus is one of the most serious foliar disease constraints for both crops in warmer growing areas and causes significant yield losses. High temperature and high relative humidity favour the outbreak of the disease, in particular in South Asia's intensive ‘irrigated wheat–rice’ production systems. In this article, we review the taxonomy and worldwide distribution, as well as strategies to counteract the disease as an emerging threat to cereal production systems. We also review the current understanding of the cytological and molecular aspects of the interaction of the fungus with its cereal hosts, which makes B. sorokiniana a model organism for studying plant defence responses to hemibiotrophic pathogens. The contrasting roles of cell death and H 2O2 generation in plant defence during biotrophic and necrotrophic fungal growth phases are discussed.

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Use of Molecular Cytology to Study the Structure and Biology of Phytopathogenic and Mycorrhizal Fungi

Hardham

Mitchell

1998

Fungal Genetics and Biology

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Immunocytochemical Localization of Phytotoxins inBipolaris sorokiniana

Cited by 12 publications

References 28 publications

Function of Native OmtA In Vivo and Expression and Distribution of This Protein in Colonies of Aspergillus parasiticus

Function of Native OmtA In Vivo and Expression and Distribution of This Protein in Colonies of Aspergillus parasiticus

Bipolaris sorokiniana, a cereal pathogen of global concern: cytological and molecular approaches towards better control‡

Use of Molecular Cytology to Study the Structure and Biology of Phytopathogenic and Mycorrhizal Fungi

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