title: A conditionally dispensable chromosome controls host-specific pathogenicity in the fungal plant pathogen Alternaria alternata.
abstract: The filamentous fungus Alternaria alternata contains seven pathogenic variants (pathotypes), which produce host-specific toxins and cause diseases on different plants. Previously, the gene cluster involved in host-specific AK-toxin biosynthesis of the Japanese pear pathotype was isolated, and four genes, named AKT genes, were identified. The AKT homologs were also found in the strawberry and tangerine pathotypes, which produce AF-toxin and ACT-toxin, respectively. This result is consistent with the fact that the toxins of these pathotypes share a common 9,10-epoxy-8-hydroxy-9-methyl-decatrienoic acid structural moiety. In this study, three of the AKT homologs (AFT1-1, AFTR-1, and AFT3-1) were isolated on a single cosmid clone from strain NAF8 of the strawberry pathotype. In NAF8, all of the AKT homologs were present in multiple copies on a 1.05-Mb chromosome. Transformation-mediated targeting of AFT1-1 and AFT3-1 in NAF8 produced AF-toxin-minus, nonpathogenic mutants. All of the mutants lacked the 1.05-Mb chromosome encoding the AFT genes. This chromosome was not essential for saprophytic growth of this pathogen. Thus, we propose that a conditionally dispensable chromosome controls host-specific pathogenicity of this pathogen.
authors.affiliation: Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya, Japan.
authors.forename: Rieko
authors.initials: R
authors.lastname: Hatta
authors.forename: Kaoru
authors.initials: K
authors.lastname: Ito
authors.forename: Yoshitsugu
authors.initials: Y
authors.lastname: Hosaki
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Tanaka
authors.forename: Aiko
authors.initials: A
authors.lastname: Tanaka
authors.forename: Mikihiro
authors.initials: M
authors.lastname: Yamamoto
authors.forename: Kazuya
authors.initials: K
authors.lastname: Akimitsu
authors.forename: Takashi
authors.initials: T
authors.lastname: Tsuge
mesh_terms: D000528:Alternaria / Q000235:genetics* / Q000472:pathogenicity*; D015825:Chromosomes, Fungal; D003360:Cosmids / Q000235:genetics; D031985:Fragaria / Q000382:microbiology; D005656:Fungal Proteins / Q000235:genetics; D018390:Gene Targeting; D005800:Genes, Fungal; D007621:Karyotyping; D016296:Mutagenesis; D009183:Mycotoxins / Q000235:genetics / Q000502:physiology; D017422:Sequence Analysis, DNA
chemical_list: D005656:Fungal Proteins; D009183:Mycotoxins