|
|
|
|
|
||
|
|||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | |||||
Journal of Cell Science, Vol 102, 611-627, Copyright © 1992 by Company of Biologists
Submitted on December 2, 1991
Accepted on March 13, 1992
1 Biology Department, York University, 4700 Keele Street, North York, Ontario M3J 1P3, Canada
2 Department of Biochemistry, Colorado State University, Fort Collins, Colorado 80523, USA
Author for correspondence
Very similar changing patterns of actin are described with rhodamine-phalloidin labelling during the zoosporic life cycle of the oomycetes, Saprolegnia ferax and Achlya bisexualis. By comparing the changes with previously described ultrastructural and functional changes, we show that actin functions in numerous previously unrecognized processes.
Most spectacularly, the directed vesicle expansions of the cytokinetic system involve newly formed actin which outlines the developing zoospores. Disruption of this actin with cytochalasins leads to abnormal cleavage as witnessed by the formation of enlarged and irregular cysts. Prior to cytokinesis, two new types of organelle are synthesized and one, known as K bodies, clusters around the nuclei. These organdies are actin-rich during development and clustering, consistent with actin functioning in their positioning.
In the zoospores, actin is concentrated around the water expulsion vacuoles, indicating that they are contractile, and permeates the cytoplasm, probably with a skeletal role. This concept is supported by the first demonstration of actin specifically associated with a microtubular root in the secondary zoospore. Upon encystment there is a dramatic increase in stained actin in the form of peripheral plaques associated with the newly synthesized cell wall.
When the cysts germinate, a fibrillar actin cap, comparable to that previously described in hyphal tips, forms in the germ tube apex, but only after cell wall softening to permit germ tube protrusion. This sequence is consistent with the actin cap modulating turgor-driven expansion of the tip as previously discussed for hyphae.
In addition to disrupting cleavage-associated actin, cytochalasins show developmental stage, dose and drug (CE
CDCB) specific effects on zoosporulation-related actin, which indicates that, contrary to previous suggestions, rhodamine-phalloidin staining is a useful indicator of actin behaviour in response to cytochalasins. These responses include differential effects on adjoining actin arrays, some of which are transient in the continued presence of the drugs, indicating a mechanism of drug adaptation.
Key words: actin, rhodamine-phalloidin, flagellate cells, cytokinesis, organelle positioning, cytochalasins, fungi, contractile vacuoles, tip growth, oomycetes
Submitted on December 2, 1991
Accepted on March 13, 1992
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati 
Twitter What's this?
This article has been cited by other articles:
|
|
 |
|
  R. R. Lew Mass flow and pressure-driven hyphal extension in Neurospora crassa Microbiology, August 1, 2005; 151(8): 2685 - 2692. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. S. Lowry, K. E. Fisher, and R. W. Roberson Functional necessity of the cytoskeleton during cleavage membrane development and zoosporogenesis in Allomyces macrogynus Mycologia, March 1, 2004; 96(2): 211 - 218. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Kopecka, M. Gabriel, K. Takeo, M. Yamaguchi, A. Svoboda, and K. Hata Analysis of microtubules and F-actin structures in hyphae and conidia development of the opportunistic human pathogenic black yeast Aureobasidium pullulans Microbiology, April 1, 2003; 149(4): 865 - 876. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C Bachewich and I. Heath Radial F-actin arrays precede new hypha formation in Saprolegnia: implications for establishing polar growth and regulating tip morphogenesis J. Cell Sci., June 8, 2000; 111(14): 2005 - 2016. [Abstract] [PDF]
|
|
|
|
|
|
N. Levina, R. Lew, and I. Heath Cytoskeletal regulation of ion channel distribution in the tip-growing organism Saprolegnia ferax J. Cell Sci., January 1, 1994; 107(1): 127 - 134. [Abstract] [PDF]
|
|
