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Beticolins, Nonpeptidic, Polycyclic Molecules Produced by the Phytopathogenic Fungus Cercospora beticola, as a New Family of Ion Channel-Forming Toxins

February 2000 , Volume 13 , Number  2
Pages  203 - 209

Cyril Goudet , 1 Marie-Louise Milat , 2 Hervé Sentenac , 1 and Jean-Baptiste Thibaud 1

1Laboratoire de Biochimie et Physiologie Moléculaire des Plantes, CNRS URA 2133/ENSA-M/INRA/UM2, 2, Place Pierre Viala, 34060 Montpellier Cedex 1, France; 2Laboratoire de Phytopharmacie et Biochimie des Interactions Cellulaires, UA 692 INRA/Université de Bourgogne, BV 1540, 21034 Dijon Cedex, France

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Accepted 19 October 1999.

Beticolins are toxins produced by Cercospora beticola, a phytopathogenic fungus responsible for the leaf spot disease of sugar beet. They form a family of 20 nonpeptidic compounds (named B0 to B19) that share the same polycyclic skeleton but differ by isomeric configuration (ortho- or para-) and by a variable residue R (bridging two carbons in one of the six cycles). It has been previously shown that B0 assembles itself into a multimeric structure and forms ion channels into planar lipid bilayers (C. Goudet, A.-A. Véry, M.-L. Milat, M. Ildefonse, J.-B. Thibaud, H.Sentenac, and J.-P. Blein, Plant J. 14:359-364, 1998). In the present work, we investigate pore formation by three ortho-beticolins, B0, B2, and B4, and their related (i.e., same R) para-isomers, B13, B1, and B3, respectively, using planarlipid bilayers. All beticolins were able to form ionchannels with multiple conductance states, although the type of cyclization (ortho- or para-) and residue (R) result in variations of channel conductance and ionic permeability, respectively. Channel formation by beticolins is likely to be involved in the biological activity of these toxins.

© 2000 The American Phytopathological Society