Ultrastructure of the host-pathogen interface in daylily leaves infected by the rust fungus Puccinia hemerocallidis

Abstract

Transmission electron microscopy was used to examine details of the host-pathogen interface in daylily leaf cells infected by the rust fungus Puccinia hemerocallidis. Samples were prepared for study by high-pressure freezing followed by freeze substitution. The outstanding preservation of ultrastructural details afforded by this fixation protocol greatly facilitated the study of this host-pathogen interface. The extrahaustorial membrane that separated each dikaryotic haustorium from the cytoplasm of its host cell was especially well preserved and appeared almost completely smooth in profile. Large aggregations of tubular cytoplasmic elements were present near haustoria in infected host cells. Many of these tubular elements were found to be continuous with the extrahaustorial membrane and conspicuous electron-dense deposits present in the extrahaustorial matrix extended into these elements. The use of gold-conjugated wheat germ agglutinin for labeling of chitin revealed that these deposits were not part of the haustorial wall. Portions of many of the tubular elements associated with haustoria were conspicuously beaded in appearance. Some tubular elements were found to be continuous with flattened cisternae that in turn bore short beaded chains. Distinctive tubular-vesicular complexes previously reported only in cryofixed rust haustoria also were found in the haustoria of P. hemerocallidis.

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

“…The haustorium of P. pimpinellae showed the ultrastructural characteristics described by other investigators for other club-shaped dikaryotic haustoria with two nuclei in their bodies (Baka, 1992;Baka and Gjaerum, 1996;Baka, 2002;Baka and Lösel, 1992a;Classen et al, 2001;Mims et al, 2002). It is generally assumed that, at maturity, two nuclei are present in the haustorium body.…”

Internalization of Flax Rust Avirulence Proteins into Flax and Tobacco Cells Can Occur in the Absence of the Pathogen

“…However, these mechanisms are not yet understood; likewise, we still know little of the uptake pathway of rust effector proteins. Ultrastructure studies have detected tubular extensions of the extrahaustorial membrane with associated budding vesicles that reach into the host cell cytoplasm and can form close contact with host ER and dictyosomes (Mims et al, 2002). Although this suggests that endocytosis may be a key process in the uptake of effector proteins, it remains to be determined what uptake pathways are involved in rust Avr protein delivery.…”

Studies on leaf spot disease of Withania somnifera and its impact on secondary metabolites

“…1a). Such protuberance could be because of the presence of a hyphal mat that accumulates beneath the epidermis [24].…”