Association of a Myosin Immunoanalogue with Cell Envelopes of Aspergillus fumigatus Conidia and Its Participation in Swelling and Germination

Abstract

A myosin immunoanalogue was identified in conidia ofAspergillus fumigatus by Western blotting, indirect immunofluorescence assay, and gold immunoelectron microscopy with two different antimyosin antibodies. The distribution pattern of this protein was followed during the early stages of germination. A single 180-kDa polypeptide, detected predominantly in a cell envelope extract, was found to cross-react with monoclonal and polyclonal antibodies raised against vertebrate muscle myosin. Immunoelectron microscopy permitted precise localization of this polypeptide, indicating that myosin analogue was mainly distributed along the plasma membrane of resting and swollen conidia. In germinating conidia, indirect immunofluorescence microscopy revealed myosin analogue at the periphery of germ tubes, whereas actin appeared as dispersed punctate structures in the cytoplasm that were more concentrated at the site of germ tube emergence. A myosin ATPase inhibitor, butanedione monoxime, greatly reduced swelling and blocked germination. In contrast, when conidia were treated with cytochalasin B, an inhibitor of actin polymerization, swelling was not affected and germination was only partially reduced. Butanedione monoxime-treated conidia showed accumulation of cytoplasmic vesicles and did not achieve cell wall reorganization, unlike swollen conidia. Collectively, these results suggest an essential role for this myosin analogue in the deposition of cell wall components during germination of A. fumigatus conidia and therefore in host tissue colonization.

Vesicular Trans-Cell Wall Transport in Fungi: A Mechanism for the Delivery of Virulence-Associated Macromolecules?

“…In yeast cells, wall remodeling for vesicle passage could be facilitated during budding, when the cell wall is thinner in the bud than in nondividing areas of the cell surface (Linnemans et al 1977). Finally, a myosin analog was described as a cell wall component of Aspergillus fumigatus (Esnault et al 1999). In the cytosolic space, motor proteins like myosin and dynein contribute with the movement of transport vesicles (Schliwa and Woehlke, 2003).…”

The cytoskeleton in plant and fungal cell tip growth

“…Myosins or myosin homologues have been identified and/or immunolocalized in numerous tip‐growing cells (fungi and oomycetes, Turian, 1988; Kaminskyj & Heath, 1996; May et al ., 1998; Esnault et al ., 1999: pollen tubes, Heslop‐Harrison & Heslop‐Harrison, 1989b; Kohno et al ., 1992; Terasaka & Niitsu, 1994; Yokota & Shimmen, 1994; Miller et al ., 1995; Yokota et al ., 1995; Cai et al ., 1997; Ren et al ., 1998: algal rhizoids, Braun, 1996). Immunolocalization denoted that myosin is present preferentially in the apical cytoplasm of hyphae (Turian, 1988; Esnault et al ., 1999) and pollen tubes (Yokota et al ., 1995; Pierson & Cresti, 1992), often associated with cytoplasmic organelles and vesicles. In pollen tubes and algal rhizoids different classes of myosin have been identified, leading to the suggestion that different types of organelle might move with the help of different types of myosin, thus exhibiting distinct characteristics of movement (Miller et al ., 1995; Braun, 1996; Cai et al ., 1997).…”

“…Inhibition of myosin ATPase activity indicated that tip growth processes, which involve the actin cytoskeleton, also require myosin activity (May et al ., 1998; Steinberg & McIntosh, 1998). In Aspergillus fumigatus myosin inhibition was even more effective than actin inhibition on bulge formation and germination, thus demonstrating its important role in these processes (Esnault et al ., 1999). The ATPase activity of myosins seems to be positively related to the growth rate of tip‐growing cells, as shown in pollen tubes of Lilium davidii (Ren et al ., 1998).…”

“…Some cell types seem to be less affected by cytoskeleton drugs than others. In Aspergillus fumicatus (Esnault et al ., 1999) and Pinus pollen (Terasaka & Niitsu, 1994) cytochalasins have only a minor effect on germination. A lack of effect of cytochalasin on root hair bulging has been observed in trichoblasts of Vicia faba which correlates to the lack of polar organization of AFs preceding bulge formation in these cells (Miller et al ., 1999).…”

Viability and infectivity of Toxoplasma gondii tachyzoites exposed to Butanedione monoxime

“…Streinberg et al evaluated the effects of BDM on the morphological characteristics of Saccharomyces species and indicated a gradual reduction in the formation and growth of colonies on Agar medium at 1-30 lm BDM concentrations (Steinberg and McIntosh 1998). In another study by Esnault et al, BDM decreased inflation and budding capability of Aspergillus Fumigatus species and led to impaired cell wall disruption (Esnault et al 1999). Furthermore, Schmidt and Wetzel et al showed that the motility and invasion of Cryptosporidium Parvum were hindered by Cytochalasin D and BDM, respectively (Wetzel et al 2005).…”