Endomembrane system of aspen root cells plays a key role in defense against a common fungal root endophyte,Cryptosporiopsis radicicola

Abstract

The host-endophyte interaction between roots of aspen (Populus tremuloides) and Cryptosporiopsis radicicola was examined primarily by transmission electron microscopy. Hyphae growing on the exterior of the inoculated roots had a thick, electron-dense, adhesive sheath. At hyphal contact and penetration, host epidermal cells exhibited a series of defense responses (viz. formation of papillae and partition walls, general wall thickening and walling-off of internal hyphae). In papilla formation, loop-shaped, rough endoplasmic reticula (rER) gave rise to globose secretory vesicles that accumulated around and then fused to the developing papilla. Unlike papillae, general wall thickening was associated with the Golgi apparatus (GA) that produced cell wall materials; 1-3 layers of Golgi cisternae were in contact with or in the immediate proximity (mostly within 0-0.5 microm) of and lying parallel to the host cell wall, where they budded out numerous subglobose vesicles that fused directly to the host cell wall and made it thicker. Partition wall formation and walling-off of internal hyphae also were common; the former was associated with an extended single cisterna, which was indistinguishable from rER or individual cisternae of GA, and in the latter phenomenon internal hyphae were encased by electron-dense material containing numerous ribosomes and membranous elements that were derived apparently from proliferated rER. These pronounced defense responses protected the stele and contributed to making C. radicicola endophytic rather than pathogenic.

Fungal root endophytes ofQuercus robursubjected to flooding

“…The aspen– P. radicicola and larch– Pezicula interactions, when evaluated on the basis of anatomical contacts and secondary metabolite production, were defined as antagonism (Tsuneda et al. ) or balanced antagonism (Schulz et al. ).…”

“…It colonizes epidermal cells and cortical regions. This results in defensive anatomical responses in the plant, which prevent the fungus from further colonization but also affect the water-conducting function and nutrient uptake of the host (Tsuneda et al 2009). Thus, the colonized plants remain asymptomatic and the fungus functions as an endophyte and not as a pathogen.…”

“…Thus, the colonized plants remain asymptomatic and the fungus functions as an endophyte and not as a pathogen. The aspen-P. radicicola and larch-Pezicula interactions, when evaluated on the basis of anatomical contacts and secondary metabolite production, were defined as antagonism (Tsuneda et al 2009) or balanced antagonism (Schulz et al 1999). The latter was involved in the creation of disease resistance correlated with concentration of phenolic metabolites in barley and larch (Schulz et al 1999).…”

New insights into the survival strategy of the invasive soilborne pathogen Phytophthora cinnamomi in different natural ecosystems in Western Australia

“…; Schulz and Boyle ; Tsuneda et al. ; Tellenbach ). In the present study, many of the affected cortex cells examined in living fine roots of the susceptible hosts B. grandis , E. marginata and X. preissii and in particular of the resistant species E. megacarpa and C. calophylla were apparently still alive even though they were partly filled with a 3‐dimensional tube‐like system of lignitubers.…”

Xylariales): Physiological characterization and structural features of its association with wheat.

“…There are very few studies that analyze the DSE plant-fungus interaction at the ultrastructural level (Peterson et al, 2008, Tsuneda et al, 2009. Here, no defense responses were found when the interaction between T. aestivum and M. bolleyi was studied with TEM, only an electronically dense material was observed around the intercellular hyphae.…”