ACTTS3 encoding a polyketide synthase is essential for the biosynthesis of ACT-Toxin and pathogenicity in the tangerine pathotype of alternaria alternata

Y. Miyamoto, A. Masunaka, T. Tsuge, Mikihiro Yamamoto, K. Ohtani, T. Fukumoto, K. Gomi, T. L. Peever, Y. Tada, K. Ichimura, K. Akimitsu

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The tangerine pathotype of Alternaria alternala produces host-selective ACT-toxin and causes Alternaria brown spot disease of tangerine and tangerine hybrids. Sequence analy-sis of a genomic BAC clone identified part of the ACT-toxin TOX (ACTT) gene cluster, and knockout experiments have implicated several open reading frames (ORF) contained within the cluster in the biosynthesis of ACT-toxin. One of the ORF, designated ACTTS3, encoding a putative poly-ketide synthase, was isolated by rapid amplification of cDNA ends and genomic/reverse transcription-polymerase chain reactions using the specific primers designed from the BAC sequences. The 7,374-bp ORF encodes a polyketide synthase with putative ß-ketoacyl synthase, acyltransferase, methyltransferase, ß-ketoacyl reductase, and phosphopante-theine attachment site domains. Genomic Southern blots demonstrated that ACTTS3 is present on the smallest chro-mosome in the tangerine pathotype of A. alternata, and the presence of ACTTS3 is highly correlated with ACT-toxin production and pathogenicity. Targeted gene disruption of two copies of ACTTS3 led to a complete loss of ACT-toxin production and pathogenicity. These results indicate that ACTTS3 is an essential gene for ACT-toxin biosynthesis in the tangerine pathotype of A. alternata and is required for pathogenicity of this fungus.

Original languageEnglish
Pages (from-to)406-414
Number of pages9
JournalMolecular Plant-Microbe Interactions
Issue number4
Publication statusPublished - Apr 2010


ASJC Scopus subject areas

  • Physiology
  • Agronomy and Crop Science

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