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We document here for the first time ultrastructural details of the cellular interaction of Asteridiella callista and its host Stachytarpheta mutabilis var. violacea from Costa Rica. A. callista attaches to the host with appressoria, invades the epidermal cell wall and forms an apoplastic complex cisternal net, presumably for nutrient uptake from its host. This unique structure, called an interaction apparatus (Ia), consists of cisternae surrounded by a membrane continuous with the fungal cytoplasmic membrane. Subsequently the apoplastic trunk of the Ia extends into the host epidermal cell wall and contacts the host cytoplasmic membrane. Electron-opaque material, probably of fungal origin appears at the host cytoplasmic membrane. Finally these electron-opaque deposits are encased by host material. Functional and systematical aspects of this interaction scenario are discussed. [ABSTRACT FROM AUTHOR]

In this study, a biomonitoring project using the moss Scorpiurum circinatum was carried out to evaluate the deposition and biological effects of heavy metals in the area of Acerra (Naples, S Italy), one of the vertices of the sadly called ¿Italian triangle of death¿ owing to the dramatic increase in tumours. The results clearly indicated that the study area is heavily polluted by heavy metals, a large proportion of which is likely present in the atmosphere in particulate form. The ultrastructural organization of exposed samples was essentially preserved, but cell membrane pits, cytoplasm vesicles and concentric multilamellar/multivesicular bodies, probably induced by pollution, were found, which may be involved in the tolerance mechanisms to metal pollution in this moss species. Although severe biological effects were not found at the ultrastructural level in the exposed moss, effects on humans, especially after long-term exposure, are to be expected. [Copyright &y& Elsevier]

Abstract: Spined conidia and hyphae of Ustilaginoidea virens were examined by light and electron microscopy. Bright-field light microscopy showed that conidia were round to elliptical and warty on the surface with diameters approximately ranging from 3 to 5μm. Scanning electron microscopy revealed the globose to irregularly rounded and ornamented conidia with prominent spines. The spines were pointed at the apex or irregularly curved, and approximately 200–500nm long. Ultrastructure of spined conidia and hyphae revealed by transmission electron microscopy showed lipid globules and vacuoles in the cytoplasm enclosed by an electron-transparent cell wall. Conspicuous electron-dense spines were evident on the surface of conidia, and had obclavate or irregularly protruding shapes with varying heights along the conidial cell wall. Microfibrillar structures with stretching or branching patterns were evident in the spine matrix. Some conidia were interconnected by spines from the neighboring conidia by their extended outgrowth. Hyphae had concentric bodies that showed an electron-transparent core surrounded by an electron-dense layer. One or more intrahyphal hyphae were found in hyphal cytoplasm. The fungus is thought to form concentric bodies and intrahyphal hyphae as survival mechanisms against the water- and nutrient-deficient environments that may occur in the necrotic regions of host plants. [Copyright &y& Elsevier]

The ultrastructure of soredia of the foliose epiphytic lichen Hypogymnia physodes cultivated on agar plates for 11 days with three different concentrations of MnCl2 (7 μM [control], 500 μM, 7 mM) was compared by means of transmission electron microscopy. Photobiont cells (Trebouxia jamesii) of Mn-exposed soredia had swollen and contracted thylakoids. The chloroplasts were reduced in size, and numerous lysosome-like vesicles occurred in cells with degenerated chloroplast. At 500 μM, autospores of T. jamesii were more severely damaged than vegetative cells. At 7 mM, autospore formation was strongly reduced. Concentric bodies and mesosome-like structures were nearly completely absent from mycobiont cells of Mn-treated soredia at both 500 μM and 7 mM. At 500 μM, the photobiont of not grown soredia was more severely damaged compared to grown soredia (defined as soredia where division of algal cells had taken place). At 7 mM, ultrastructural damage was observed in both grown and not grown soredia. This suggests that even soredia that survived the first days of cultivation are probably not capable of forming thalli on Mn-rich substrates. The ultrastructural changes in Mn-exposed soredia support the hypothesis that high Mn concentrations in bark or stemflow are a limiting factor for the abundance of H. physodes and other epiphytic lichens in coniferous forests of Europe and North America. [Copyright &y& Elsevier]

Ultrastructural examinations revealed concentric bodies in hyphae of a parasitic ascomycete, infecting pollen of Malva sylvestris ssp.mauritiana. These structures consist of three concentric zones and are similar to those found in mycobionts of several lichens and only a few nonlichenized ascomycetes. Typical septal pores of ascomycete hyphae were present, usually plugged by electron-dense material and associated with one or more Woronin bodies. [ABSTRACT FROM AUTHOR]

The pyenidium of a Stagonospora sp. observed in degenerating leaf sheath and blade tissues of Lolium perenne L. contained concentric bodies similar to those found in the mycobiont of several lichens and a few other free-living ascomycetes. These bodies occurred in vegetative hyphae, hyphae of the pycnidial wall, in conidiogenous cells and in conidia and comprised a central electron-translucent core surrounded by a granular zone and an outer radially orientated fibrillar or lamellar zone. In some cases the entire body was surrounded by a translucent halo. A second feature of the interwoven hyphae of the pycnidial wall was the occurrence of pores connecting adjacent hyphae. These lateral pores appeared identical to pores in septa between cells of individual hyphae, and like them, were associated with Woronin bodies. [ABSTRACT FROM AUTHOR]