Structural and Functional Complexity of the Genomic Region Controlling AK-Toxin Biosynthesis and Pathogenicity in the Japanese Pear Pathotype of Alternaria alternata
The Japanese pear pathotype of Alternaria alternata produces host-specific AK-toxin and causes black spot of Japanese pear. Previously, a cosmid clone, pcAKT-1, was isolated that contains two genes, AKT1 and AKT2, within a 5.0-kb region required for AK-toxin biosynthesis. The wild-type strain has mu...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
The American Phytopathological Society
2000-09-01
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| Series: | Molecular Plant-Microbe Interactions |
| Online Access: | https://apsjournals.apsnet.org/doi/10.1094/MPMI.2000.13.9.975 |
| Summary: | The Japanese pear pathotype of Alternaria alternata produces host-specific AK-toxin and causes black spot of Japanese pear. Previously, a cosmid clone, pcAKT-1, was isolated that contains two genes, AKT1 and AKT2, within a 5.0-kb region required for AK-toxin biosynthesis. The wild-type strain has multiple, nonfunctional copies of these genes. In the present study, two additional genes, AKTR-1 and AKT3-1, downstream of AKT2 were identified. Transformation of the wild type with AKTR-1- and AKT3-1-targeting vectors produced toxin-deficient (Tox¯), nonpathogenic mutants. DNA gel blot analysis, however, demonstrated that the fragments targeted in Tox¯ mutants were different from those containing AKTR-1 and AKT3-1 on the transforming vectors. A cosmid clone, pcAKT-2, containing the targeted DNA was isolated and shown to carry two genes, AKTR-2 and AKT3-2, with high similarity to AKTR-1 and AKT3-1, respectively. Transcripts from not only AKTR-2 and AKT3-2 but also AKTR-1 and AKT3-1 were found in the wild type. DNA gel blot analysis with pulsed-field gel electrophoresis showed that AKT1, AKT2, AKT3, and AKTR and their homologues are on a single chromosome. These results indicate the structural and functional complexity of the genomic region controlling AK-toxin biosynthesis. |
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| ISSN: | 0894-0282 1943-7706 |