Protoplasmic Organization of Hyphal Tips Among Fungi: Vesicles and Spitzenkörper

Abstract

Hyphal tips of fungi representing OQmycetes, Zygomycetes, Ascomycetes, Basidiomycetes, and Deuteromycetes were examined by light and electron microscopy and compared with respect to their protoplasmic organization. In all fungi studied, there is a zone at the hyphal apex which is rich irn cytoplasmic vesicles but nearly devoid of other cell components. Some vesicle profiles are continuous with the plasma membrane at the apices of these tip-growing cells. The subapical zones of hyphae contain an endomembrane system which includes smooth-surfaced cisternae associated with small clusters of vesicles. The findings are consistent with the hypothesis that vesicles produced by the endomembrane system in the subapical region become concentrated in the apex where they are incorporated at the expanding surface. Septate fungi (Ascomycetes, Basidiomycetes, and Deuteromycetes) have an apical body (Spitzenkorper) which is associated with growing hyphal tips. In electron micrographs of these fungi, an additional specialized region within the accumulation of apical vesicles is shown for the first time. This region corresponds on the bases of distribution among fungi, location in hyphae, size, shape and boundary characteristics to the Spitzenkorper seen by light microscopy. This structure is not universally associated with tip growth, whereas apical vesicles are widespread among tip-growing systems.

Branched absorbing structures (BAS): a feature of the extraradical mycelium of symbiotic arbuscular mycorrhizal fungi

“…To the best of our knowledge the present work describes for the first time the cytological features of for many fungal hyphae (Grove & Bracker, 1970 ;Sward, 1981) BAS hyphae can be divided into three developmental zones : (i) apical zone ; (ii) subapical zone ; and (iii) mature (vacuolation) zone. (i) Apical zones of BAS extend 4-5 µm back from the hyphal tips.…”

Clathrin localization and dynamics in Aspergillus nidulans

“…Despite the supposed ubiquity of clathrin in eukaryotic endocytosis, coated vesicles have rarely been seen in micrographs produced by transmission electron microscopy in hyphae and other filamentous fungal cell types (Bracker, 1967;Grove and Bracker, 1970;Howard, 1981;That et al, 1987;Hoffmann and Mendgen, 1998;Fischer-Parton et al, 2000;Hohmann-Marriott et al, 2006;Bourett et al, 2007), and whether endocytosis in filamentous fungi is primarily clathrin-dependent or Clathrin in A. nidulans 311 independent has remained unresolved. Mechanisms for clathrin-independent endocytosis are well known in mammals and have recently been analyzed in yeast, where they are controlled by proteins generally associated with actin cables, such as formin (Prosser et al, 2011;Mayor et al, 2014).…”

Acute inactivation of the Aspergillus nidulans Golgi membrane fusion machinery: correlation of apical extension arrest and tip swelling with cisternal disorganization

“…One is the Spitzenkörper, a structure located underneath the apical plasma membrane. Ultrastructural studies have shown that the Spitzenkörper largely consists of vesicles (Grove and Bracker, 1970;Howard, 1981;Hohmann-Marriott et al, 2006). Intermingled with these vesicles is a dense mesh of actin microfilaments (Hohmann-Marriott et al, 2006), corresponding to the apical spot seen with GFP-actin and Lifeact-GFP/TagRFP in A. nidulans and Neurospora crassa respectively (Taheri-Talesh et al, 2008;Berepiki et al, 2010).…”