Allelic Variation in the Effector Genes of the Tomato Pathogen Cladosporium fulvum Reveals Different Modes of Adaptive Evolution
The allelic variation in four avirulence (Avr) and four extracellular protein (Ecp)–encoding genes of the tomato pathogen Cladosporium fulvum was analyzed for a worldwide collection of strains. The majority of polymorphisms observed in the Avr genes are deletions, point mutations, or insertions of t...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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The American Phytopathological Society
2007-10-01
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| Series: | Molecular Plant-Microbe Interactions |
| Subjects: | |
| Online Access: | https://apsjournals.apsnet.org/doi/10.1094/MPMI-20-10-1271 |
| Summary: | The allelic variation in four avirulence (Avr) and four extracellular protein (Ecp)–encoding genes of the tomato pathogen Cladosporium fulvum was analyzed for a worldwide collection of strains. The majority of polymorphisms observed in the Avr genes are deletions, point mutations, or insertions of transposon-like elements that are associated with transitions from avirulence to virulence, indicating adaptive evolution of the Avr genes to the cognate C. fulvum resistance genes that are deployed in commercial tomato lines. Large differences in types of polymorphisms between the Avr genes were observed, especially between Avr2 (indels) and Avr4 (amino-acid substitutions), indicating that selection pressure favors different types of adaptation. In contrast, only a limited number of polymorphisms were observed in the Ecp genes, which mostly involved synonymous modifications. A haplotype network based on the polymorphisms observed in the effector genes revealed a complex pattern of evolution marked by reticulations that suggests the occurrence of genetic recombination in this presumed asexual fungus. This, as well as the identification of strains with identical polymorphisms in Avr and Ecp genes but with opposite mating-type genes, suggests that development of complex races can be the combined result of positive selection and genetic recombination. |
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| ISSN: | 0894-0282 1943-7706 |