Abstract
The filamentous fungus Alternaria alternata encompasses seven distinct pathogenic variants, commonly referred to as pathotypes, each renowned for producing unique host-specific toxins that lead to various plant diseases. Previously, researchers isolated the gene cluster responsible for the synthesis of the host-specific AK-toxin associated with the Japanese pear pathotype, identifying four crucial genes designated as AKT genes. Notably, homologs of these AKT genes were discovered within the strawberry and tangerine pathotypes, which are known to produce AF-toxin and ACT-toxin, respectively. This aligns with the observation that the toxins associated with these pathotypes share a fundamental structural component: a 9,10-epoxy-8-hydroxy-9-methyl-decatrienoic acid moiety. In our study, we successfully isolated three of the AKT homologs—AFT1-1, AFTR-1, and AFT3-1—from a singular cosmid clone sourced from the NAF8 strain of the strawberry pathotype. Our findings revealed that, in strain NAF8, all AKT homologs were represented in multiple copies located on a chromosome measuring 1.05 megabases. Using transformation-mediated targeting, we generated AF-toxin-deficient, nonpathogenic mutants by manipulating genes AFT1-1 and AFT3-1 in NAF8. Notably, these mutants completely lacked the 1.05-Mb chromosome that encodes the AFT genes, further demonstrating that this chromosome is non-essential for the saprophytic growth of the pathogen. Consequently, we propose a paradigm in which a conditionally dispensable chromosome governs the host-specific pathogenicity of this remarkable fungal pathogen.
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Selected References
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Articles from Genetics are provided here courtesy of Oxford University Press
How do the molecular karyotypes of *Alternaria* plant pathogens influence their ability to produce host-specific toxins?
It seems you’re sharing references from scientific literature focusing on fungal genetics and pathogens, specifically involving *Alternaria* fungi and their ability to produce host-specific toxins. Here’s a summary of the items you’ve mentioned:
1. **Molecular Karyotypes for Alternaria Plant Pathogens**
– **Authors:** H. Akamatsu, M. Taga, M. Kodama, R. Johnson, H. Otani
– **Published in:** Current Genetics, 1999
– **DOI:** 10.1007/s002940050464
– **Focus:** The study presents molecular karyotypes relevant to *Alternaria* plant pathogens that produce specific toxins targeted to particular hosts.
2. **Gapped BLAST and PSI-BLAST**
– **Authors:** S. F. Altschul et al.
– **Published in:** Nucleic Acids Research, 1997
– **DOI:** 10.1093/nar/25.17.3389
– **Focus:** This seminal paper introduces enhancements to protein database search programs that improve bioinformatics research.
3. **New Cosmid Vectors for Library Construction in Filamentous Fungi**
– **Authors:** Z. An et al.
– **Published in:** Gene, 1996
– **DOI:** 10.1016/0378-1119(96)00225-9
– **Focus:** Discusses the development of new vectors for constructing genomic libraries, enhancing molecular biology techniques in filamentous fungi.
4. **Nuclear Ribosomal DNA Variation and Pathogenic Specialization in Alternaria Fungi**
– **Authors:** M. Kusaba, T. Tsuge
– **Published in:** Applied and Environmental Microbiology, 1994
– **DOI:** 10.1128/aem.60.9.3055-3062.1994
– **Focus:** Examines the variation in nuclear ribosomal DNA as it relates to the pathogenic specialization of *Alternaria* species known for producing toxins.
5. **A Fungal Gene for Antibiotic Resistance on a Dispensable (“B”) Chromosome**
– **Authors:** V. P. Miao, S. F. Covert, H. D. VanEtten
– **Published in:** Science, 1991
- **DOI:** 10.1126/science.1763326
– **Focus:** Reports the identification of a gene associated with antibiotic resistance located on a dispensable chromosome in fungi, which has implications for understanding resistance mechanisms.
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