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Functional Analysis of the Cytochrome P450 Monooxygenase Gene bcbot1 of Botrytis cinerea Indicates That Botrydial Is a Strain-Specific Virulence Factor

June 2005 , Volume 18 , Number  6
Pages  602 - 612

Verena Siewers , 1 Muriel Viaud , 2 Daniel Jimenez-Teja , 3 Isidro G. Collado , 3 Christian Schulze Gronover , 1 Jean-Marc Pradier , 2 Bettina Tudzynsk , 1 and Paul Tudzynski 1

1Institut für Botanik, Westf. Wilhelms-Universität Münster, Schlossgarten 3, D-48149 Münster, Germany; 2Unité de Phytopathologie et Meéthodologies de la Détection, Institut National de la Recherche Agronomique, Route de Saint-Cyr, F-78086 Versailles, France; 3Departamento de Quimica Organica, Facultad de Ciencias, Universidad de Cádiz, Apdo. 40, E-11510 Puerto Real, Spain

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Accepted 6 February 2005.

The micrographic phytopathogen Botrytis cinerea causes gray mold diseases in a large number of dicotyledonous crop plants and ornamentals. Colonization of host tissue is accompanied by rapid killing of plant cells ahead of the growing hyphen, probably caused by secretion of nonspecific phytotoxins, e.g., the sesquiterpene botrydial. Although all pathogenic strains tested so far had been shown to secrete botrydial and although the toxin causes comparable necrotic lesions as infection by the fungus, the role of botrydial in the infection process has not been elucidated so far. Here, we describe the functional characterization of bcbot1, encoding a P450 monooxygenase and provide evidence that it is involved in the botrydial pathway, i.e., it represents the first botrydial biosynthetic gene identified. We show that bcbot1 is expressed in planta and that expression in vitro and in planta is controlled by an α-subunit of a heterotrimeric GTP-binding protein, BCG1. Deletion of bcbot1 in three standard strains of B. cinerea shows that the effect on virulence (on several host plants) is strain-dependent; only deletion in one of the strains (T4) led to reduced virulence.

Additional keywords: secondary metabolism , signaling .

© 2005 The American Phytopathological Society