Dissection of the host range of the fungal plant pathogen Alternaria alternata by modification of secondary metabolism

Kaoru Ito, Takayoshi Tanaka, Rieko Hatta, Mikihiro Yamamoto, Kazuya Akimitsu, Takashi Tsuge

Research output: Contribution to journalArticlepeer-review

80 Citations (Scopus)


The filamentous fungus Alternaria alternata contains seven pathogenic variants (pathotypes), which produce different host-specific toxins and cause diseases on different plants. The strawberry pathotype produces host-specific AF-toxin and causes Alternaria black spot of strawberry. This pathotype is also pathogenic to Japanese pear cultivars susceptible to the Japanese pear pathotype that produces AK-toxin. The strawberry pathotype produces two related molecular species, AF-toxins I and II: toxin I is toxic to both strawberry and pear, and toxin II is toxic only to pear. Previously, we isolated a cosmid clone pcAFT-1 from the strawberry pathotype that contains three genes involved in AF-toxin biosynthesis. Here, we have identified a new gene, designated AFTS1, from pcAFT-1. AFTS1 encodes a protein with similarity to enzymes of the aldo-ketoreductase superfamily. Targeted mutation of AFTS1 diminished the host range of the strawberry pathotype: ΔaftS1 mutants were pathogenic to pear, but not to strawberry, as is the Japanese pear pathotype. These mutants were found to produce AF-toxin II, but not AF-toxin I. These data represent a novel example of how the host range of a plant pathogenic fungus can be restricted by modification of secondary metabolism.

Original languageEnglish
Pages (from-to)399-411
Number of pages13
JournalMolecular Microbiology
Issue number2
Publication statusPublished - Apr 2004
Externally publishedYes

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology


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