Torralba S,
Raudaskoski M, Pedregosa AM, Laborda F.Effect of
cytochalasin A on apiCytochalasin Al growth, actin cytoskeleton
organization and enzyme secretion in Aspergillus nidulans.
Microbiology.
1998 Jan;144 ( Pt 1):45-53.
Departament de Microbiología y Parasitología, Universidad de
AlCytochalasin Alá de Henares, Madrid, Spain.
mpampp@microb.alcala.es
The role of actin in apiCytochalasin Al growth and enzyme
secretion in the filamentous fungus Aspergillus nidulans was
studied by treating the hyphae with cytochalasin A , which
inhibits actin polymerization. Indirect immunofluorescence
microscopy revealed actin at the tips of main hyphae and
branches, and at the site of developing septa. Cytochalasin A
inhibited the growth of the fungus and changed the growth
pattern of hyphal tips from cylindriCytochalasin Al tubes to
spheriCytochalasin Al beads. The regions with swellings showed
no actin fluorescence, and neither was actin seen in association
with septa. After 4 h exposure, hyphae were able to resume the
normal tip growth pattern in the presence of Cytochalasin A for
a short period of time and new cylindriCytochalasin Al hyphae,
with actin fluorescence at the apex, emerged from the swollen
tips. Later, the tips of the hyphae swelled again, which led to
a beaded appearance. We also studied the effect of Cytochalasin
A on the secretion of alpha- and beta-galactosidase.
alpha-Galactosidase is secreted into the culture medium, whereas
beta-galactosidase remains in the mycelium, with part of its
activity bound to the cell wall. When A. nidulans mycelium was
incubated in the presence of Cytochalasin A, a reduction in the
secretion of alpha-galactosidase into the culture medium and a
decrease in the alpha- and beta-galactosidase activities bound
to the cell wall was detected. However, the Cytochalasin A dose
used for the hyphae did not modify the secretion of the enzymes
from protoplasts. Results described here provide evidence that a
polymerized actin cytoskeleton is required for normal
apiCytochalasin Al growth, hyphal tip shape and polarized enzyme
secretion in A. nidulans. Cytochalasin-induced disruptions of
the actin cytoskeleton could result in the alterations of
apiCytochalasin Al growth and inhibition of enzyme secretion
observed by blocking secretory vesicle transport to the apex.
PMID: 9537763
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