A putative branched-chain-amino-acid transaminase gene required for HC-toxin biosynthesis and pathogenicity in Cochliobolus carbonum

Yi Qiang Cheng, Joong Hoon Ahn, Jonathan D. Walton

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26 Scopus citations

Abstract

The cyclic tetrapeptide HC-toxin is required for pathogenicity of the filamentous fungus Cochliobolus carbonum on maize. HC-toxin production is controlled by a complex locus, TOX2. The isolation and characterization of a new gene of the TOX2 locus, TOXF, is reported. It is shown that TOXF is specifically required for HC-toxin production and pathogenicity. It is present as two or three copies in all HC-toxin-producing (Tox2+) isolates and is absent in toxin-non-producing strains. The deduced amino acid sequence of TOXF has moderate homology to many known or putative branched-chain-amino-acid transaminases from various species. A strain of C. carbonum with all copies of TOXF disrupted grew normally but lost HC-toxin production and pathogenicity. It is proposed that TOXF has a biosynthetic role in HC-toxin synthesis, perhaps to aminate a precursor of Aeo (2-amino-9, 10-epoxi-8-oxodecanoic acid).

Original languageEnglish
Pages (from-to)3539-3546
Number of pages8
JournalMicrobiology
Volume145
Issue number12
DOIs
StatePublished - Dec 1999

Keywords

  • Branched-chain-amino-acid transaminase
  • Cochliobolus (Helminthosporium) carbonum
  • Cyclic peptide
  • HC-toxin
  • TOXF

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