title: Function of genes encoding acyl-CoA synthetase and enoyl-CoA hydratase for host-selective act-toxin biosynthesis in the tangerine pathotype of Alternaria alternata.
abstract: The tangerine pathotype of Alternaria alternata produces host-selective ACT-toxin and causes Alternaria brown spot disease. Sequence analysis of a genomic cosmid clone identified a part of the ACTT gene cluster and implicated two genes, ACTT5 encoding an acyl-CoA synthetase and ACTT6 encoding an enoyl-CoA hydratase, in the biosynthesis of ACT-toxin. Genomic Southern blots demonstrated that both genes were present in tangerine pathotype isolates producing ACT-toxin and also in Japanese pear pathotype isolates producing AK-toxin and strawberry pathotype isolates producing AF-toxin. ACT-, AK-, and AF-toxins from these three pathotypes share a common 9,10-epoxy-8-hydroxy-9-methyl-decatrienoic acid moiety. Targeted gene disruption of two copies of ACTT5 significantly reduced ACT-toxin production and virulence. Targeted gene disruption of two copies of ACTT6 led to complete loss of ACT-toxin production and pathogenicity and a putative decatrienoic acid intermediate in ACT-toxin biosynthesis accumulated in mycelial mats. These results indicate that ACTT5 and ACTT6 are essential genes in ACT-toxin biosynthesis in the tangerine pathotype of A. alternata and both are required for full virulence of this fungus.
authors.affiliation: United Graduate School and Faculty of Agriculture, Kagawa University, Miki, Kagawa 761-0795 Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Miyamoto
authors.forename: Y
authors.initials: Y
authors.lastname: Ishii
authors.forename: A
authors.initials: A
authors.lastname: Honda
authors.forename: A
authors.initials: A
authors.lastname: Masunaka
authors.forename: T
authors.initials: T
authors.lastname: Tsuge
authors.forename: M
authors.initials: M
authors.lastname: Yamamoto
authors.forename: K
authors.initials: K
authors.lastname: Ohtani
authors.forename: T
authors.initials: T
authors.lastname: Fukumoto
authors.forename: K
authors.initials: K
authors.lastname: Gomi
authors.forename: T L
authors.initials: TL
authors.lastname: Peever
authors.forename: K
authors.initials: K
authors.lastname: Akimitsu
mesh_terms: D000528:Alternaria / Q000201:enzymology / Q000235:genetics* / Q000472:pathogenicity; D002957:Citrus / Q000382:microbiology; D003066:Coenzyme A Ligases / Q000235:genetics*; D004746:Enoyl-CoA Hydratase / Q000235:genetics*; D005800:Genes, Fungal; D023281:Genomics; D054884:Host-Pathogen Interactions / Q000235:genetics; D009183:Mycotoxins / Q000096:biosynthesis*; D014774:Virulence
chemical_list: D009183:Mycotoxins; D004746:Enoyl-CoA Hydratase; D003066:Coenzyme A Ligases