2007 Fiscal Year Final Research Report Summary
Evolution and differentiation of plant pathogenic fungi mediated by pathogenicity chromosomes
| Project/Area Number |
18580041
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Plant pathology
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| Research Institution | Tottori University |
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Principal Investigator |
KODAMA Motoichiro Tottori University, Faculty of Agriculture, Professor (00183343)
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| Co-Investigator(Kenkyū-buntansha) |
OTANI Hiroshi Tottori University, Faculty of Agriculture, Professor (50032305)
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| Project Period (FY) |
2006 – 2007
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| Keywords | plant pathogen / pathogenicity gene / CD chromosome / host-specific toxin |
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| Research Abstract |
The tomato pathotype of A. alternata (A. alternata f. sp. lycopersici) produces host-specific AAL-toxins and causes Alternaria stem canker. A 120 kb genomic region that contains the AAL-toxin biosynthetic (ALT) gene cluster in the tomato pathotype was sequenced and compared with corresponding sequences of the fumonisin biosynthetic (FUM) gene cluster in Gibberella moniliformis. The genomic region includes 19 putative ORFs and 12 of those showed similarity to the genes in the FUM gene cluster. The ALT gene cluster resides on a 1.0 Mb conditionally dispensable chromosome (CDC) found only in the pathogenic and AAL-toxin-producing strains of A. alternata, and homologues of the genes were not detected in non-pathogenic strains of A. alternata. Genomic sequences of ALT1 and another PKS gene located outside of the ALT gene cluster, both of which reside on CDCs in the tomato pathotype strains were compared to tomato pathotype strains collected worldwide. This revealed that the sequences of the genes located on the CDCs, in the strains with different geographical origins, are identical. On the other hand, sequences of other genes located on the chromosomes other than CDCs are not identical in each strain, indicating that the origin of the CDCs might be different from other chromosomes in the tomato pathotype. We propose a hypothesis whereby the ability to produce AAL-toxins determining specific pathogenicity of the pathogen could be potentially distributed among A. alternata strains by horizontal transfer of the CDCs, and thus provide a possible mechanism whereby new pathogens can arise in nature.
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