Functional, Organizational, and Biochemical Analysis of Actin in Hyphal Tip Cells of Allomyces macrogynus

Srinivasan, Srijayanthi; Vargas, Maria M.; Roberson, Robert W.

doi:10.2307/3760784

Cited by 40 publications

(44 citation statements)

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“…The primary effect of cytochalasins is the inhibition of actin polymerization (Srinivasan et al, 1996) but these compounds also affect functions not yet known to be related to the actin cytoskeleton, such as glucose transport across cell membranes (Lin 8c Spudich, 1974) and mitochondria1 respiration (Manavanthu et al, 1980). In the present work, the effect of different concentrations of CA on the growth of A. nidulans mycelium in both solid (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…However, these studies have not led to conclusive results (Howard & Aist, 1980 , 1996). Cytochalasins are known for their ability to inhibit polymerization of actin in uivo and can be used to study the functions of the actin cytoskeleton (Srinivasan et al, 1996). Among cytoskeletal components, actin seems to be the most important for apical growth in yeast and in filamentous fungi (Heath, 1990).…”

Section: Introductionmentioning

confidence: 99%

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Effect of cytochalasin A on apical growth, actin cytoskeleton organization and enzyme secretion in Aspergillus nidulans

et al. 1998

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The role of actin in apical growth and enzyme secretion in the filamentous fungus Aspery(illuJ nidulans was studied by treating the hyphae with cytochalasin A (CA), which inhibits actin polymerization. Indirect immunofluorescence microscopy revealed actin at the tips of main hyphae and branches, and a t the sites of developing septa. CA inhibited the growth of the fungus and changed the growth pattern of hyphal tips from cylindrical tubes to spherical 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 CA for a short period of time and new cylindrical hyphae, with actin fluorescence a t the apex, emerged from the swollen tips. Later, the tips of the hyphae swelled again, which led to a beaded apperance. We also studied the effect of CA on the secretion of a-and pgalactosidase. a-Galactosidase is secreted into the culture medium, whereas pgalactosidase remains in the mycelium, with part of its activity bound to the cell wall. When A. nidulans mycelium was incubated in the presence of CA, a reduction in the secretion of a-galactosidase into the culture medium and a decrease in the a-and / % galactosidase activities bound to the cell wall was detected. However, the CA 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 apical growth, hyphal tip shape and polarized enzyme secretion in A. nidulans. Cytochalasin-induced disruptions of the actin cytoskeleton could result in the alterations of apical growth and inhibition of enzyme secretion observed by blocking secretory vesicle transport to the apex.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of cytochalasin A on apical growth, actin cytoskeleton organization and enzyme secretion in Aspergillus nidulans

et al. 1998

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“…Tip growth, as seen in fungal hyphae, moss protonemata, pollen tubes and root hairs, is a highly polarized process with extension occurring purely at the apex (Heath, 1990;Hepler et al, 2001). F-actin is a vital component of tip growth, being concentrated at the apex and with growth disruption resulting from exposure to anti-actin drugs (Bachewich & Heath, 1998;Geitmann & Emons, 2000;Heath, 2000;Heath et al, 2000;Ketelaar et al, 2003;Srinivasan et al, 1996;). …”

Section: Introductionmentioning

confidence: 99%

The dynamic behaviour of microtubules and their contributions to hyphal tip growth in Aspergillus nidulans

Sampson

Heath

2005

Microbiology

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Creating and maintaining cell polarity are complex processes that are not fully understood. Fungal hyphal tip growth is a highly polarized and dynamic process involving both F-actin and microtubules (MTs), but the behaviour and roles of the latter are unclear. To address this issue, MT dynamics and subunit distribution were analysed in a strain of Aspergillus nidulans expressing GFP-a-tubulin. Apical MTs are the most dynamic, the bulk of which move tipwards from multiple subapical spindle pole bodies, the only clear region of microtubule nucleation detected. MTs populate the apex predominantly by elongation at rates about three times faster than tip extension. This polymerization was facilitated by the tipward migration of MT subunits, which generated a tip-high gradient. Subapical regions of apical cells showed variable tubulin subunit distributions, without tipward flow, while subapical cells showed even tubulin subunit distribution and low MT dynamics. Short MTs, of a similar size to those reported in axons, also occasionally slid into the apex. During mitosis in apical cells, MT populations at the tip varied. Cells with less distance between the tip and the first nucleus were more likely to loose normal MT populations and dynamics. Reduced MTs in the tip, during mitosis or after exposure to the MT inhibitor carbendazim (MBC), generally correlated with reduced, but continuing growth and near-normal tip morphology. In contrast, the actin-disrupting agent latrunculin B reduced growth rates much more severely and dramatically distorted tip morphology. These results suggest substantial independence between MTs and hyphal tip growth and a more essential role for F-actin. Among MT-dependent processes possibly contributing to tip growth is the transportation of vesicles. However, preliminary ultrastructural data indicated a lack of direct MT-organelle interactions. It is suggested that the population of dynamic apical MTs enhance migration of the 'cytomatrix', thus ensuring that organelles and proteins maintain proximity to the constantly elongating tip.

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“…Likewise, physiological studies have demonstrated the existence of protons gradients, Ca 2+ and an abundance of cytoskeletal proteins in the tip region (Turian, 1981;Turian, 1983;Schmid and Harold, 1988;Jackson and Heath, 1993;Barja et al, 1991;Barja et al, 1993;Gow, 1994;Robson et al, 1996;Srinivasan et al, 1996;Hyde and Heath, 1997). The presence of Spitzenköper in chytridiomycetes was not known until recently.…”

Section: Discussionmentioning

confidence: 99%

“…In growing hyphal tips many investigators have documented the abundance of cytoskeletal proteins (Jackson and Heath, 1990;Kaminskyj and Heath, 1995;Barja et al, 1993;Huber and Ojha, 1994;Srinivasan et al, 1996), Ca 2+ (Jackson and Heath, 1993;Hyde and Heath, 1997) and the presence of a pH gradient (Robson et al, 1996). The intracellular pH gradient (a pH of 8.2 in the tip and 6.8 in the distal region) in the growing hyphae of N. crassa showed a steep correlation between the magnitude and length of the pH gradient and the rate of hyphal extension (Robson et al, 1996).…”

Section: Discussionmentioning

confidence: 99%

Spatial and cellular localization of calcium-dependent protease (CDP II)inAllomyces arbuscula

Ojha

Barja

2003

Journal of Cell Science

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Immunogold labeling of calcium-dependent neutral protease II (CDPII) with specific antibodies in near median longitudinal ultrathin sections of Allomyces arbuscula showed that the enzyme is predominantly localized in the growing hyphal and rhizoidal apices. The tips in both cell type had more enzyme than the distal regions and showed a gradient distribution. Labeling of the ultrathin sections and western blot analysis of purified subcellular fractions showed that CDPII is mainly cytosolic. Catalytic activity of the enzyme measured with synthetic substrate (Bz-Arg-pNA) showed that 90% of its activity is present in the soluble fraction, although a small amount is associated with the nuclei (0.2%), plasma membranes (0.7%) and microsomes (3.9%). This association is discussed in the context of the functional role of the enzyme and its possible localized activation. Western blot analysis of the crude extract and indirect immunofluorescence of the fixed permeabilized hypahe after treatment with CDPII showed that theα-tubulin is a specific target of the enzyme.

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Functional, Organizational, and Biochemical Analysis of Actin in Hyphal Tip Cells of Allomyces macrogynus

Cited by 40 publications

References 0 publications

Effect of cytochalasin A on apical growth, actin cytoskeleton organization and enzyme secretion in Aspergillus nidulans

Effect of cytochalasin A on apical growth, actin cytoskeleton organization and enzyme secretion in Aspergillus nidulans

The dynamic behaviour of microtubules and their contributions to hyphal tip growth in Aspergillus nidulans

Spatial and cellular localization of calcium-dependent protease (CDP II)inAllomyces arbuscula

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