Surface Morphology, Wall Structure, and Initial Adhesion of Conidia of the Powdery Mildew Fungus<i>Uncinuliella australiana</i>

Mims, C.

doi:10.1094/phyto-85-352

Cited by 24 publications

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“…1994). Initial adhesion could also depend on the presence of extracellular material deposited on the spore surface to ensure attachment of the spore to the plant surface, as has been postulated for powdery mildew fungi (Mims et al 1995;Nicholson and Kunoh 1995). For U. necalor.…”

Section: Discussionmentioning

confidence: 97%

An important role for secreted esterase in disease establishment of the wheat powdery mildew fungus Blumeria graminis f. sp.tritici

et al. 2011

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Development and adhesion of infection structures of the grapevine powdery mildew fungus. U~cinu/a necator (Schw.) Burr.. were investigated during the early stages of leaf colonization. Light microscopy showed that primary appressoria occurred 3.5 h post inoculation (p.i.) and that hyphae on the leaf surface, indicative of successful host colonization, appeared 14 h p.i. Low temperature scanning electron microscopy revealed deposits of extracellular material at the contact zone of fungal structures and plant cuticle, suggesting firm attachment of the pathogen. To investigate whether or not esterase or cutinase activity is involved in establishing the fungus on the host cuticle, histochemical assays and inhibitor studies were performed. Results indicated that esterase activity was associated with conidia and infection structures. A single fungal extracellular protein was identified as a cutinase by its ability to hydrolyze 3H-cutin. Probing Southern blots of genomic DNA of U necalor, Magnaporlhe grisea, and Fusarium so/ani fsp. pisi with the cutinase gene of F so/ani fsp. pisi suggested that the cutinase gene of U necalor shares only limited sequence similarities with the cutinase genes of the other fungi investigated. Adhesion assays showed that the presence of esterase-cutinase inhibitors on the cuticle did not significantly affect adhesion. The role of the enzyme in fungal adhesion is discussed.Key words: grapevine powdery mildew, Vilis vinifera, cutinase, extracellular matrix, cryofixation, low temperature scanning electron microscopy.Resume: Le developpement et l' adhesion 'des structures infectieuses du champignon de I' o"idium de la vigne, Uncinu/a necator (Schw.) Burr., ont ete etudies pendant les premiers stades de la colonisation de la feuille. La microscopie optique a revele un appressorium primaire 3.5 h apres inoculation (p.i.) et un hyphe sur la feuil1e, indiquant le succes de la colonisation. 14 h p.i. En microscopie electronique it balayage des dep6ts de materiel extracellulaire ont pu etre observes sur la zone de contact entre les structures fongiques et la cuticule de la plante, suggerant un attachement ferme du pathogene. Pour rechercher si une activite cutinase ou esterase participait it l'etablissement du champignon sur la cuticule de l'h6te, des etudes histochimiques et avec des inhibiteurs ont ete conduites. Elles ont montre que l'activite esterase etait associee avec les conidies et les structures infectieuses. Une seule protei ne fongique extracel1ulaire a ete identifiee comme une cutinase par sa capacite it hydrolyser de la 3H-cutine. Des Southern blots d' ADN genomique d' U necalor. Magnaporlhe grisea et Fusarium so/ani fsp. pisi utilisant corn me probe le gene de la cutinase de F so/ani fsp. pisi suggerent que le gene de la cutinase d' U necator ne partage que peu de zones de similarite de sequence avec les genes de la cutinase des autres especes etudiees. Des essais d' adhesion ont montre que la presence d' inhibiteurs d' esterase-cutinase sur la cuticule n' affectent pas sig...

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Section: Discussionmentioning

confidence: 97%

An important role for secreted esterase in disease establishment of the wheat powdery mildew fungus Blumeria graminis f. sp.tritici

et al. 2011

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“…Conidia of M. grisea stick to the repellant surface of rice plants by releasing an adhesive from the apex of the spore. This release is triggered by wetting of the conidium [27]. The surface of conidia from the powdery mildew fungus Uncinuliella australiana is coated with a thin network of extracellular mucilage which on contact with a wet surface, spreads instantly to form sticky adhesion pads [28].…”

Section: Conidial Adhesionmentioning

confidence: 99%

The molecular mechanisms of conidial germination

Osherov

2001

FEMS Microbiology Letters

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The asexual spore, or conidium, is critical in the life cycle of many fungi because it is the primary means for dispersion and serves as a`safe house' for the fungal genome in adverse environmental conditions. This review discusses the physiological process of germination, conidial adhesion and initiation of protein synthesis and also the regulatory pathways used to activate conidial germination. These include Ca 2 / calmodulin-mediated signaling, the cyclic AMP/protein kinase A and the ras/mitogen-activated protein kinase pathways. Insights into the process of conidial germination will increase our understanding of the mechanisms of dormancy and sensing of environmental stimuli, and permit identification of novel therapeutic targets for the treatment of spore-borne fungal infections in plants and animals. ß

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“…By necessity, adhesion must be a rapid process and to facilitate this fungal spores are either precoated with adhesive or contain stores of preformed adhesive material ready for rapid release. The conidia of both the powdery mildew Unicinuliella australiana (Mims et al, 1995a) and the aquatic Hyphomycete Mycocentrospora filiformis (Au et al, 1996) are examples of the former situation. The conidia of these species are coated with mucilage which acts to instantly attach them to a suitable surface.…”

Section: Adhesionmentioning

confidence: 99%

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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Surface Morphology, Wall Structure, and Initial Adhesion of Conidia of the Powdery Mildew FungusUncinuliella australiana

Cited by 24 publications

References 0 publications

An important role for secreted esterase in disease establishment of the wheat powdery mildew fungus Blumeria graminis f. sp.tritici

An important role for secreted esterase in disease establishment of the wheat powdery mildew fungus Blumeria graminis f. sp.tritici

The molecular mechanisms of conidial germination

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

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