Irregular growth forms and cell wall modifications, polygalacturonase detection, and endocell formation in Fusarium oxysporum f. sp. radicis-lycopersici infecting tomato plants, as studied ultrastructurally and cytochemically

Simard

et al. 2005

Uncommon, opaque particles (of approximately 20-22 nm, referred to as OP), aggregating into paracrystalloids occurred only next to colonized cells in carnation plants of either a susceptible or resistant cultivar (cv.) infected with Fusarium oxysporum f.sp. dianthi. In the susceptible plant, those structures occurred in vessel lumina and host walls, apparently associated with their alterations, but not in parenchyma cells, a situation which was the exact opposite of that observed in resistant plants. In comparison with apparently similar structures reported in other systems, paracrystalloids and their OPs did not seem to have exact counterparts in plants infected with viruses or fungi, although similar paracrystalloids were observed in nematode-infected plants. The OPs were associated in both cvs. with fine opaque matter, often displaying fine filamentous structures, and were in addition connected to fungal cells in the susceptible cv. Similar structures also extended through host walls into adjoining cells; these relations with parenchyma cells in resistant plants were interpreted as if the particles therein were akin to, if not exactly of the same nature as those in susceptible plants. As the opaque matter, the filamentous structures and the OPs were interrelated and associated with pathogen cells, it seemed warranted to assume that the OPs were issued from the pathogen.

Section: Discussionsupporting

confidence: 82%

Occurrence of paracrystalloids and their particles in resistant and susceptible carnation plants infected with Fusarium oxysporum f.sp. dianthi race 2

Simard

et al. 2005

“…For example, O. novo-ulmi growing in its hosts as well as on various substrates, including growth through Millipore membranes (Ouellette et al 1995), may produce various irregular growth forms and subsequently revert to so-called typical growth forms. Similar irregular growth forms were reported for Fusarium infection in carnation and tomato (Charest et al 2004;Ouellette et al 2001). …”

Section: Introductionsupporting

confidence: 80%

“…If they were of pathogen origin, it means that they could maintain a potential for infection, as shown here and in other works for more typical larger fungal cells with defective walls, particularly in microhyphae spanning, non septate, long distances in host cell walls (Charest et al 2004;Ouellette et al 2001Ouellette et al , 2002Ouellette et al , 2004a, for example). Alterations or absence of fungal walls in hyphae penetrating host walls have numerous gold particles have attached to large IEs which are delimited solely by opaque bands.…”

Section: Discussionsupporting

confidence: 59%

Peculiar ultrastructural characteristics of fungal cells and of other elements apposed to and in vessel walls in plants of a susceptible carnation cultivar, infected with Fusarium oxysporum f.sp. dianthi race 2

Baayen²,

et al. 2005

Ultrastructural characteristics and cytochemical reactions of unusual, irregular elements (IE) in vessel elements in susceptible carnation plants infected with Fusarium oxysporum are reported. As revealed by labelling for chitin, fungal cells in contact with host cell walls or content had altered or defective lucent layers, and labelling was frequently associated with their outer, opaque layer or matter located outside the cells. Coating matter on vessel walls occurred at all stages of infection, and IEs only in later stages. IEs were delineated by opaque, often folded bands, some contouring pit borders, and contained membranous and vesicular structures mixed with other fine components. Only then, IEs were strongly but not uniformly labelled for chitin. Coating, IE-delineating bands, and the opaque outer layer of typical fungal cells were texturally similar, not labelled for chitin or cellulose, except where they impinged upon host walls. Both probes for chitin and cellulose strongly attached to vessel secondary walls. IEs were often confluent with coating, and with fungal cells connected to them by means of microfilamentous structures. Similar microfilamentous structures and opaque bands connected to IEs, the coating, and the microhyphae, or protruding from fungal cells reached into host walls, associated with alterations of these walls. The possible malleable IEs might be a counterpart of the coating, and although they do not occur in the initial stages of the disease, they could play an important role in the final stages of tissue degradation.

“…Observations of the apparent absence of a nuclear envelope in some fungal cells in the present study are also similar to those of O. novo-ulmi and of other F. oxysporum f. spp. (Chamberland and Ouellette 1977a;Charest et al 2004;Ouellette et al 2004c). It is not impossible that the components of high opacity in this OM concealed some structural DNA (see Fig.…”

Section: Discussionmentioning

confidence: 88%

Histopathology of Fusarium wilt of staghorn sumac (Rhus typhina) caused by Fusarium oxysporum f. sp. callistephi race 3. II. Characteristics of opaque matter associated with extensive host cell and cell wall alterations

Simard

2006

Self Cite

AbstractLight and transmission electron microscopy observations of staghorn sumac plants inoculated or naturally infected withFusarium oxysporumf. sp.callistephiare reported. One aspect of infection was the presence of large intercellular masses of opaque matter (OM) in middle lamellae between ray cells and/or fibres, often bypassing several intercellular areas; similar OM confluent with the intercellular OM also occurred in secondary walls and in the periphery of numerous cells. A gradual increase in the abundance of the OM in host tissues vertically from the inoculation point and then radially was noted over infection time and was related to host wall and cell alterations. In the region of recently deposited tissue, the OM was associated with pronounced cell hyperplasia and hypertrophy. The OM was delimited by thin, compact bands, and when it was less compact, displayed opaque particles and other fine structures. No indications were obtained that it contained or had contained intact or altered organelles. The DNA probe bound to OM in middle lamellae and in cell periplasmic areas, and to material of a similar texture lining vessel walls. Samples fromFusarium-infected plants, incubated on an agar medium before fixing to determine from which elements the pathogens could develop, displayed bodies as the sole elements present in mature xylem cells and in intercellular areas. These bodies were delimited by membranous structures and profiles of a wall layer and contained opaque particles and areas of fine structures. Certain inter- or intracellular fungal cells in the same tissue frequently had similar content. In the light of these observations it is proposed that the OM is primarily of a pathogen rather than of a host origin.