ISSN:
1432-2048
Keywords:
Actin
;
Calmodulin
;
Ernodesmis
;
Membrane skeleton
;
Microfilaments
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Ultrastructural changes in the cortical cytoskeleton during wound-induced cytoplasmic contraction were examined in the coenocytic green alga Ernodesmis verticillata. Both calmodulin (CaM) and actin were localized in intact and contracting cells by immunogold labeling. Within 5 min after wounding, compact microfilament (MF) bundles were observed which increase in diameter as cytoplasmic contraction proceeds. Calmodulin labeling is associated with amorphous material studding the MF bundles, whereas actin labeling occurs along the individual MFs. No MF bundles were ever observed during contraction that were not also labeled with anti-CaM antibodies. In cells treated with the CaM antagonist W-7 (N-[6-aminohexyl]-5-chloro-1-naphtha-lenesulfonamide), MF bundles do not form, and the formation of loosely arranged MFs (similar to nascent bundles in untreated cells) is greatly retarded. We propose that CaM binds indirectly to actin by activating an actin-binding regulatory protein which functions in early stages of the transduction sequence leading to functional MF bundles. Additionally, ultrastructural evidence is presented for a plasma-membrane skeleton or undercoating in this alga.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00201493
