The Botrytis cinerea phytotoxin botcinic acid requires two polyketide synthases for production and has a redundant role in virulence with botrydial

Authors

  • BÉRENGÈRE DALMAIS,

    1. Unité de Recherches BIOGER-CPP, INRA, Avenue Lucien Brétignières, 78850 Thiverval-Grignon, France
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    • These authors contributed equally to this work.

  • JULIA SCHUMACHER,

    1. Institut für Botanik der Westfälischen Wilhelms-Universität Münster, Schlossgarten 3, D-48149 Münster, Germany
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    • These authors contributed equally to this work.

  • JAVIER MORAGA,

    1. Departamento de Química Orgánica, Facultad de Ciencias, Universidad de Cádiz, 11510 Puerto Real, Spain
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    • These authors contributed equally to this work.

  • PASCAL LE PÊCHEUR,

    1. Unité de Recherches BIOGER-CPP, INRA, Avenue Lucien Brétignières, 78850 Thiverval-Grignon, France
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  • BETTINA TUDZYNSKI,

    Corresponding author
    1. Institut für Botanik der Westfälischen Wilhelms-Universität Münster, Schlossgarten 3, D-48149 Münster, Germany
      Email: bettina.tudzynski@uni-muenster.de; isidro.gonzalez@uca.es; viaud@versailles.inra.fr
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  • ISIDRO GONZALEZ COLLADO,

    Corresponding author
    1. Departamento de Química Orgánica, Facultad de Ciencias, Universidad de Cádiz, 11510 Puerto Real, Spain
      Email: bettina.tudzynski@uni-muenster.de; isidro.gonzalez@uca.es; viaud@versailles.inra.fr
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  • MURIEL VIAUD

    Corresponding author
    1. Unité de Recherches BIOGER-CPP, INRA, Avenue Lucien Brétignières, 78850 Thiverval-Grignon, France
      Email: bettina.tudzynski@uni-muenster.de; isidro.gonzalez@uca.es; viaud@versailles.inra.fr
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Email: bettina.tudzynski@uni-muenster.de; isidro.gonzalez@uca.es; viaud@versailles.inra.fr

SUMMARY

The grey mould fungus Botrytis cinerea produces two major phytotoxins, the sesquiterpene botrydial, for which the biosynthesis gene cluster has been characterized previously, and the polyketide botcinic acid. We have identified two polyketide synthase (PKS) encoding genes, BcPKS6 and BcPKS9, that are up-regulated during tomato leaf infection. Gene inactivation and analysis of the secondary metabolite spectra of several independent mutants demonstrated that both BcPKS6 and BcPKS9 are key enzymes for botcinic acid biosynthesis. We showed that BcPKS6 and BcPKS9 genes, renamed BcBOA6 and BcBO9 (for B. cinerea botcinic acid biosynthesis), are located at different genomic loci, each being adjacent to other putative botcinic acid biosynthetic genes, named BcBOA1 to BcBOA17. Putative orthologues of BcBOA genes are present in the closely related fungus Sclerotinia sclerotiorum, but the cluster organization is not conserved between the two species. As for the botrydial biosynthesis genes, the expression of BcBOA genes is co-regulated by the Gα subunit BCG1 during both in vitro and in planta growth. The loss of botcinic acid production does not affect virulence on bean and tomato leaves. However, double mutants that do not produce botcinic acid or botrydial (bcpks6Δbcbot2Δ) exhibit markedly reduced virulence. Hence, a redundant role of botrydial and botcinic acid in the virulence of B. cinerea has been demonstrated.

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