The Galpha subunit BCG1 is essential for pathogenicity of the grey mould fungus Botrytis cinerea. Several processes such as the transition from primary
infection to secondary invasive growth and the production of the phytotoxin
botrydial are regulated by BCG1 via a cAMP-independent pathway. Our recent finding that the
botrydial biosynthesis genes belong to the group of Ca(2+)/
calcineurin-dependent genes suggested for the first time a connection between this Galpha subunit and the
calcineurin signalling pathway. To investigate whether this co-regulation of genes by BCG1 and
calcineurin is a common feature, a
cDNA macroarray approach was used to compare the gene expression pattern of the wild-type and the Deltabcg1 mutant, non-treated or treated with the
calcineurin inhibitor cyclosporin A. We identified three sets of genes whose expression was regulated either by both BCG1 and
calcineurin, or only by one of them. Among the BCG1/
calcineurin-co-regulated genes, we found a new gene cluster coding for a yet unknown
polyketide secondary metabolite. Furthermore, we show for the first time in a phytopathogenic fungus that the
phospholipase C (BcPLC1) is a component of the BCG1- and
calcineurin-dependent signalling pathway as several BCG1- and
calcineurin-dependent genes were downregulated in bcplc1 knock-down mutants.