ISSN:
1615-6102
Keywords:
Brefeldin A
;
Callose
;
Cell wall
;
Golgi apparatus
;
Onion inner epidermis
;
Signal transduction
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Summary The antibiotic fungal toxin brefeldin A (BFA) causes synthesis of additional cell wall material in adult differentiated onion inner epidermal cells at concentrations of 5–30 μg/ml. This tertiary wall contains callose and is layered on the secondary cellulosic wall in a time- and dose-dependent manner. Initially, callose is found in pit fields in the form of small vesicular patches. With time and dose, depositions grow in size and form large plugs invaginating into the cell, where the adjacent cytoplasm forms bulky accumulations and contains many organelles including endomembranes. Within the cytoplasm, BFA exerts the characteristic morphological effects on the secretory system including changes of the Golgi stacks, formation of large vesicles, and proliferation of dilated cisternae of the endoplasmic reticulum. Higher concentrations of BFA (60 μg/ml) lead to disintegration of the Golgi apparatus; they have no effects on the cell wall, no callose synthesis occurs. We conclude from these observations that BFA has two independent targets in onion cells. BFA acts on the plasma membrane, hence operating as an elicitor of plant defense reactions and thus activates callose synthesis. BFA acts also on the membranes of the secretory system and influences budding and fusion of vesicles at the endoplasmic reticulum and at the dictyosomes. These two mechanisms occur in parallel, suggesting that the secretory system still can play its presumed role in callose synthesis. Only when dictyosomes are completely disintegrated, no more callose is formed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01282925
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