Expression profiles of genes encoded by the supernumerary chromosome controlling AM-toxin biosynthesis and pathogenicity in the apple pathotype of Alternaria alternata

Yoshiaki Harimoto, Rieko Hatta, Motoichiro Kodama, Mikihiro Yamamoto, Hiroshi Otani, Takashi Tsuge

Research output: Contribution to journalArticle

41 Citations (Scopus)

Abstract

The apple pathotype of Alternaria alternata produces host-specific AM-toxin and causes Alternaria blotch of apple. Previously, we cloned two genes, AMT1 and AMT2, required for AM-toxin biosynthesis and found that these genes are encoded by small, supernumerary chromosomes of <1.8 Mb in the apple pathotype strains. Here, we performed expressed sequence tag analysis of the 1.4-Mb chromosome encoding AMT genes in strain IF08984. A cDNA library was constructed using RNA from AM-toxin-producing cultures. A total of 40,980 clones were screened with the 1.4-Mb chromosome probe, and 196 clones encoded by the chromosome were isolated. Sequence analyses of these clones identified 80 unigenes, including AMT1 and AMT2, and revealed that the functions of 43 (54%) genes are unknown. The expression levels of the 80 genes in AM-toxin-producing and nonproducing cultures were analyzed by real-time quantitative polymerase chain reaction (PCR). Most of the genes were found to be expressed in both cultures at markedly lower levels than the translation elongation factor 1-α gene used as an internal control. Comparison of the expression levels of these genes between two cultures showed that 21 genes, including AMT1 and AMT2, were upregulated (>10-fold) in AM-toxin-producing cultures. Two of the upregulated genes were newly identified to be involved in AM-toxin biosynthesis by the gene disruption experiments and were named AMT3 and AMT4. Thus, the genes upregulated in AM-toxin-producing cultures contain ideal candidates for novel AM-toxin biosynthetic genes.

Original languageEnglish
Pages (from-to)1463-1476
Number of pages14
JournalMolecular Plant-Microbe Interactions
Volume20
Issue number12
DOIs
Publication statusPublished - Dec 2007

Keywords

  • Host-specific toxin

ASJC Scopus subject areas

  • Physiology
  • Agronomy and Crop Science

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