Localized accumulation of cell wall mannoproteins and endomembranes induced by brefeldin A in hyphal cells of the dimorphic yeastCandida albicans

Abstract

Summary.Candido albicans, a dimorphic yeast, has the abililty to switch its growth form between budding growth and hyphal growth. Since fungal growth involves secretory processes, spatial control of secretion should play a crucial role in such a morphogenetic transition. Brefeldin A (BFA), an inhibitor of the membrane trafficking system of eukaryotes, increases the occurrence of Golgi-like cisternae in the yeast. In the present study, BFA was used to obtain further insights into the spatial organization of secretory processes in hyphal growth of C. albicans. BFA completely inhibited the formation and growth of germ tubes at a concentration of 35 .aM or higher. Electron microscopy of BFA-untreated germinated cells revealed many vesicles in the apical region and Golgi-like eistemae in the cytoplasm. In cells treated with 35 .aM BFA, the vesicles disappeared from the apical region, and, instead, stacked membrane cisternae and membrane-enclosed spherical dense bodies accumulated in the subapical region. These accumulated structures were positive for both polysaccharide staining and immunocytochemical staining with antibodies raised against cell surface antigens of C. albicans, as were Golgi cisternae in BFA-untreated cells. In cells treated with a higher concentration of BFA (140 `aM), the structures that appeared in cells treated with 35 aM BFA were no longer observed and the endoplasmic reticulum was extended and positive for polysaccharide staining. These results suggested that BFA affects different steps of membrane trafficking in a concentration-dependent manner. The accumulated structures induced by 35 ,aM BFA seemed to be the altered forms of Golgi cistemae. Their accumulation in the subapical region of the germ tube might indicate that tile step(s) in membrane trafticking that are associated with the Golgi pathway are vectorially organized in hyphal growth of C. albicans.

A Study of the Protein Secretory Pathway of Aspergillus niger Using a Glucoamylase–GFP Fusion Protein

“…In mammalian cells, BFA treatment results in the rapid arrest of secretion, accumulation of secretory proteins in the ER, disassembly of Golgi apparatus, and the mixing of the Golgi and ER membranes (Klausner et al, 1992). However, in contrast, BFA treatment does not generally appear to promote Golgi disassembly in the fungi but does lead to ER proliferation, suggesting that BFA inhibits ER to Golgi transport (Hayashi et al, 1982;Morré , 1990;Rupeš et al, 1995;Bourett and Howard, 1996;Akashi et al, 1997;Cole et al, 2000). This would account in this study for the lack of punctate fluorescence in BFA-treated cells, and the fluorescence staining of the ER seen in this study as transport of the fusion protein from the ER to the Golgi would be blocked.…”

Community participation in biofilm matrix assembly and function

“…Mannan accumulation was blocked with tunicamycin (TM), an antibiotic that inhibits N-glycosylation, and α-mannosidase, an enzyme that catalyzes the hydrolysis of terminal mannosides. We also examined the impact of Brefeldin A (BFA), an inhibitor of anterograde transport between the ER and the Golgi, with the goal of impairing matrix deposition of both mannan and β-1,6 glucan, as these are transported through the secretory pathway (28,29). The concentrations of agents used did not inhibit planktonic or biofilm growth or alter cellular morphology (Fig.…”

Brefeldin A induces callose formation in onion inner epidermal cells

“…The local distribution of callose depositions is correlated with the distribution of Golgi bodies because BFA in low doses leads to an activation of cytoplasmic streaming and hence to a clustering of organelles in bulky domains of cytoplasm where later callose is deposited, ttere also dictyosomes accumulate, similar to the aggregates of Golgi bodies in maize cells (Satiat-Jeunemaitre et aL 1996), where they form a so-called BFA complex (Satiat-Jeunemaitre et al 1992a), and to the aggregation of Golgi equivalents in yeast ~ Akashi et al 1997) and fungal hyphae (Bourett and Howard 1996).…”