Ultrastructure and cytochemistry of extramural substances associated with intercellular hyphae of several rust fungi

HARDER, D. E., CHONG, 1., RoHRJNGER, R., MENDGEN, K., SCHNEIDER, A., WELTER, K., and KNAUF, G. 1989. lTItrastruc ture and cytochemistry of extramural substances associated with intercellular hyphae of several rust fungi. Can. J. Bot. 67: 2043-205l. Several types of extramural substance(s) associated with rust fungal intercellular hyphae were identified using a variety of tissue processing techniques. With conventional glutaraldehyde-OsO. fixing and uranyl acetate - lead citrate staining, little material could be discerned on the hyphal surfaces in nonsporulating areas except at locations of cell-cell contact, where a lightly staining fibrous or darker staining amorphous material was apparent. Freeze-substitution or freeze-fracturing pre served greater amounts Of coating material, which could be distinguished from the outer fungal wall layers. In freeze substituted samples the extramural material was amorphous in nonsporulating areas, whereas near sporulating zones it had a fibrous consistency, with the fibrils oriented perpendicularly to the fungal wall. At locations of cell-cell contact there was additional extramural material that was composed of randomly oriented fibrils or was amorphous and densely staining. All types of extramural material stained positively with the periodate - thiocarbahydrazide - silver proteinate or periodate chromate-phosphotungstate stains, but Concanavalin A bound only to some of the dense 'amorphous material. Sodium ethoxide etching and platinum -carbon shadowing also revealed the extramural material. When rust-infected wheat leaves were flooded with suspensions of colloidal gold, adhesion of gold particles occurred outside the hyphal walls and coincided with the location of extramural material. HARDER, D. E., CHONG, J., ROHRJNGER, R., MENDGEN, K., SCHNEIDER, A., WELTER, K., et KNAUF, G. 1989. lTItrastruc ture and cytochemistry of extramural substances associated with intercellular hyphae of several rust fungi. Can. J. Bot. 67 : 2043 - 205l. En traitaDt les tissus de diverses fa90ns, les auteurs ont pu identifier plusieurs types de substance(s) parietales associees avec les hyphes intra-cellulaires de rouille. En traitant avec la methode conventionnelle soit la fixation au gluteralde hyde-OsO. et la coloration a l'acetate d'uranyle - citrate de plomb, tres peu de materiel peut etre rni.s en evidence sur la surface des hyphes dans les regions non-sporulantes, excepte aux endroits de contacts intercellulaires ou on observe un mate riel fibreux legerement colore ou un mareriel amorphe plus fortement colore .. La substitution en congelation ou le cryo decapage conservent de plus grandes quantires de materiel de recouvrement qU'on peut distinguer des couches parietales externes du champignon. Dans les echantillons' 'substitues en congelation, le marerie1 extra-parietal des regions non sporulantes est amorphe, alors que dans les regions en sporulation il montre une consistance fibreuse, avec des fibrilles orientes perpendiculairement par rapport a la paroi fongique. Aux sites de contacts inter-cellulaires, il y a du materiel extra parietal additionnel compose de fibres orientees au hazard, ou amorphe et densement colore. Tous les types de materiel extra-parietal prennent la coloration avec le periodate - chromo-phosphotungstate d'argent proteine ou le periodate chromo-phosphotungstate, mais laConcanavaline A ne s'attache qu'a du mareriel amorphe dense. Le traitement a l'ethoxyde de sodium et l'ombrage au platine-carbone revelent egalement le materiel extra-parietal. Lorsqu'on immerge des feuilles de ble infectees par la rouille dans une suspension d'or collOIdal, l'adhesion des particules d'or se fait a l'exterieur des parois de l'hyphe et coincide avec la localisation du materiel extra-parietal. [Traduit par la revue]