Complex regulation of secondary metabolism controlling pathogenicity in the phytopathogenic fungus Alternaria alternata

Shinya Takaoka, Mariko Kurata, Yoshiaki Harimoto, Rieko Hatta, Mikihiro Yamamoto, Kazuya Akimitsu, Takashi Tsuge

Research output: Contribution to journalArticlepeer-review

19 Citations (Scopus)

Abstract

The filamentous fungus Alternaria alternata includes seven pathogenic variants (pathotypes), which produce different host-selective toxins and cause disease on different plants. The Japanese pear, strawberry and tangerine pathotypes produce AK-toxin, AF-toxin and ACT-toxin, respectively, which have a common structural moiety, 9,10-epoxy-8-hydroxy-9-methyl-decatrienoic acid (EDA). Here, we identified a new gene, AKT7 (AK-toxin biosynthetic gene 7), from the Japanese pear pathotype, which encodes a cytochrome P450 monooxygenase and functions to limit AK-toxin production. AKT7 homologs were found in the strawberry pathotype, but not the tangerine pathotype. However, the strawberry pathotype homolog appeared to include a premature stop codon. Although the Japanese pear pathotype strain has multiple copies of AKT7, a single-copy disruption resulted in mutants with increased production of AK-toxin and EDA. AKT7 overexpression in the three pathotypes caused marked reductions of toxin and EDA production, suggesting that Akt7 catalyzes a side reaction of EDA or its precursor. AKT7 overexpression caused reduced virulence in these pathotypes. We also found that AKT7 transcripts predominantly include misspliced mRNAs, which have premature stop codons. Our observations suggest that the AK-toxin production required for full virulence is regulated in a complex way by the copy number and intron information content of AKT7.

Original languageEnglish
Pages (from-to)1297-1309
Number of pages13
JournalNew Phytologist
Volume202
Issue number4
DOIs
Publication statusPublished - Jun 2014

Keywords

  • Alternaria alternata
  • Biosynthetic gene cluster
  • Cytochrome P450 monooxygenase
  • Host-selective toxin
  • Secondary metabolism
  • Splicing error

ASJC Scopus subject areas

  • Physiology
  • Plant Science

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