7-Dehydrobrefeldin A, a naturally occurring brefeldin A derivative, inhibits secretion and causes a cis-to-trans breakdown of Golgi stacks in plant cells.
7-Dehydrobrefeldin A (7-oxo-BFA) is a brefeldin A (BFA) analog that, like BFA, is a potent phytotoxin of Alternaria carthami, a fungal pathogen of safflower (Carthamus tinctorius L.) plants. Both BFA and 7-oxo-BFA have been shown to be causal agents of the leaf spot disease of these plants. We have investigated the effects of 7-oxo-BFA on the secretion and the structure of the Golgi stacks of sycamore maple (Acer pseudoplatanus) suspension-cultured cells to determine whether 7-oxo-BFA affects these cells in the same manner as BFA. When applied at 10 micrograms/mL for 1 h, 7-oxo-BFA inhibits secretion of proteins by approximately 80%, the same value obtained for BFA. However, electron micrographs of high-pressure frozen/freeze-substituted cells demonstrated that 7-oxo-BFA is a more potent disrupter of the Golgi stacks of sycamore maple cells than BFA. In cells treated for 1 h with 10 micrograms/mL 7-oxo-BFA, very few Golgi stacks can be discerned. Most of those that are left consist of fewer than three cisternae, all of which stain like trans-Golgi cisternae. They are surrounded by clusters of large (150-300 nm in diameter), darkly staining vesicles that are embedded in a fine-filamentous, ribosome-excluding matrix. Similarly sized and stained vesicles are seen budding from the rims of the residual trans-Golgi cisternae. Both the large vesicles and the residual Golgi stack buds stain with anti-xyloglucan polysaccharide antibodies. Recovery of Golgi stacks after removal of 7-oxo-BFA from 1-h-treated cells takes 2 to 6 h, compared with 1 to 2 h for cells treated with BFA. In contrast to 7-oxo-BFA, the BFA breakdown product BFA acid had no effect either on secretion or on the secretory apparatus. This is the first report, to our knowledge of a BFA analog inhibiting secretion in a eukaryotic cell system.
Driouich
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A
Centre National de la Recherche Scientifique Unité de Recherche Associée 203, Université de Rouen, Mont Saint Aignan, France.
Jauneau
A
A
Staehelin
L A
LA
D020126:Brefeldin A; D002478:Cells, Cultured; D003517:Cyclopentanes / Q000494:pharmacology; D005057:Eukaryotic Cells / Q000187:drug effects; D006056:Golgi Apparatus / Q000187:drug effects* / Q000648:ultrastructure; D007783:Lactones / Q000494:pharmacology*; D009183:Mycotoxins / Q000494:pharmacology*; D010940:Plant Proteins / Q000378:metabolism*; D014197:Trees / Q000187:drug effects* / Q000648:ultrastructure
D003517:Cyclopentanes; D007783:Lactones; D009183:Mycotoxins; D010940:Plant Proteins; D020126:Brefeldin A; C104900:7-dehydrobrefeldin A