title: The P450 monooxygenase BcABA1 is essential for abscisic acid biosynthesis in Botrytis cinerea.
abstract: The phytopathogenic ascomycete Botrytis cinerea is known to produce abscisic acid (ABA), which is thought to be involved in host-pathogen interaction. Biochemical analyses had previously shown that, in contrast to higher plants, the fungal ABA biosynthesis probably does not proceed via carotenoids but involves direct cyclization of farnesyl diphosphate and subsequent oxidation steps. We present here evidence that this "direct" pathway is indeed the only one used by an ABA-overproducing strain of B. cinerea. Targeted inactivation of the gene bccpr1 encoding a cytochrome P450 oxidoreductase reduced the ABA production significantly, proving the involvement of P450 monooxygenases in the pathway. Expression analysis of 28 different putative P450 monooxygenase genes revealed two that were induced under ABA biosynthesis conditions. Targeted inactivation showed that one of these, bcaba1, is essential for ABA biosynthesis: DeltaBcaba1 mutants contained no residual ABA. Thus, bcaba1 represents the first identified fungal ABA biosynthetic gene.
authors.affiliation: Institut für Botanik, Westfälische Wilhelms-Universität Münster, Schlossgarten 3, 48149 Münster, Germany.
authors.forename: Verena
authors.initials: V
authors.lastname: Siewers
authors.forename: Jørn
authors.initials: J
authors.lastname: Smedsgaard
authors.forename: Paul
authors.initials: P
authors.lastname: Tudzynski
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D001483:Base Sequence; D020171:Botrytis / Q000378:metabolism*; D002338:Carotenoids / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000502:physiology*; D008969:Molecular Sequence Data
chemical_list: D002338:Carotenoids; D000040:Abscisic Acid; D003577:Cytochrome P-450 Enzyme System