A Botrytis cinerea putative 3-keto reductase gene (ERG27) that is homologous to the mammalian 17β-hydroxysteroid dehydrogenase type 7 gene (17β-HSD7)

Botrytis cinerea (anamorph of Botryotinia fuckeliana) is a filamentous ascomycete that causes grey mould on grapevine. We had previously described two distinct populations, named HydR1 and non-HydR1, that comprise two distinct genetic entities based on genetic polymorphism, natural resistance towards the fungicide hydroxyanilide fenhexamid, and vegetative incompatibility between them. Here, we used PCR to isolate the 3-keto reductase gene ERG27 by virtue of sequence homology with Saccharomyces cerevisiae ERG27. The gene product was longer than the yeast's enzyme but possessed the main characteristic features of reductases. It displayed striking homology with mammalian 17beta-HSD7, therefore confirming the hypothesis of a common function between Erg27p like protein and 17beta-HSD7 in sterol biosynthesis (i.e. cholesterol, ergosterol). On the other hand, we analysed the polymorphism of the B. cinerea gene product and found a dozen of amino-acid differences between strains of HydR1 and non-HydR1 types that could underlie HydR1 natural resistance to fenhexamid. First, this polymorphism analysis showed that HydR1 strains form a homogeneous group distinct from the non-HydR1 group of strains. These results support our hypothesis that HydR1 and non-HydR1 strains constitute two different species. Second, Erg27p like protein sequence analysis showed that a high resistant phenotype to fenhexamid, HydR3, found in treated populations of non-HydR1 strains, had two mutations ( usually found in mammalian 17beta-HSD7) that could be useful as population markers.