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

Abstract

G. 1989. lTItrastructure 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 preserved greater amounts Of coating material, which could be distinguished from the outer fungal wall layers. In freezesubstituted 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 periodatechromate-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. lTItrastructure 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 gluteraldehyde-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 materiel fibreux legerement colore ou un mareriel amorphe plus fortement colore . . La substitution en congelation ou le cryodecapage 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 nonsporulantes 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 extraparietal additionnel compose de fibres orientees au hazard, ou...

High Pressure Freezing of Rust Infected Plant Leaves

“…5e) and that of Arachis hypogea (PNA-Gold) (Fig. 5f) as described by Rohringer et al [30] and Harder et al [8]. A quite dense labeling with both lectins was observed over the cytoplasm of the host plant, Vicia faba and the parasite U. viciae-fabae.…”

Ultrastructure of the dikaryotic stage of anise rust, Puccinia pimpinellae (F. Strauss) Link.

“…The extramural substances between intercellular hyphae and host cell wall may have adhesive function and related to the establishment of compatibility or incompatibility. Harder et al (1989) concluded that these substances appear to be highly complex and variable according to the location of the hyphae within the rust colony. Components of this material of fungal origin may well be involved in adhesive functions, in conjunction with material of host origin and are thought to consist basically of glycoprotein (Harder et al, 1989).…”

“…These hyphal cells possess two nuclei, each with one nucleolus, mitochondria and glycogen appeared as electron-lucent areas (Plate 3A). An amorphous material (extramural substances as named by Harder et al, 1989) is present between the hyphae and host cell wall (Plate 3A).…”

Impact of freeze substitution on biological electron microscopy

“…Freeze-substituted fungal infection structures like appressoria, intercellular hyphae and haustoria are very clearly visualized. Ultrastructural studies have been performed on appressoria of Magnaporthe grisea (Howard et al, 19911, on intercellular hyphae of various rust fungi (Harder et al, 1989) and fungal haustoria: e.g., the apple scab fungus Venturia inaequalis on apple leaves (Dahmen and Hobot, 1986;Studer et al, 1988Studer et al, , 1989, the bean rust Uromyces appendiculatus on bean (Welter et al, 1988;Knauf et al, 1989;Mendgen et al, 19911, and wheat stem rust Puccinia graminis fsp. tritici (Figs.…”

“…Several types of extramural substance(s) associated with the intercellular hyphae of various rust fungi have been localized using freeze substitution of HPfrozen material (Harder et al 1989). Considerably less material has been discerned on the hyphal surface after conventional preparation.…”