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MPG1 Encodes a Fungal Hydrophobin Involved in Surface Interactions during Infection-Related Development of
N. J. Talbot1, M. J. Kershaw, G. E. Wakley
1Department of Biological Sciences, University of Exeter, Washington Singer Laboratories, Perry Road, Exeter EX4 4QG, United Kingdom.
Abstract:
The rice blast fungus expresses a pathogenicity gene, MPG1, during appressorium formation, disease symptom development, and conidiation. The MPG1 gene sequence predicts a small protein belonging to a family of fungal proteins designated hydrophobins. Using random ascospore analysis and genetic complementation, we showed that MPG1 is necessary for infection-related development of Magnaporthe grisea on rice leaves and for full pathogenicity toward susceptible rice cultivars. The protein product of MPG1 appears to interact with hydrophobic surfaces, where it may act as a developmental sensor for appressorium formation. Ultrastructural studies revealed that MPG1 directs formation of a rodlet layer on conidia composed of interwoven ~5-nm rodlets, which contributes to their surface hydrophobicity. Using combined genetic and biochemical approaches, we identified a 15-kD secreted protein with characteristics that establish it as a class I hydrophobin. The protein is able to form detergent-insoluble high molecular mass complexes, is soluble in trifluoroacetic acid, and exhibits mobility shifts after treatment with performic acid. The production of this protein is directed by MPG1.
Insights
The MPG1 gene is crucial for the rice blast fungus Magnaporthe grisea to infect rice plants. This gene encodes a hydrophobin protein essential for infection-related development and pathogenicity.
Area of Science:
- Plant Pathology
- Mycology
- Molecular Biology
Background:
- The rice blast fungus, Magnaporthe grisea, causes significant crop damage.
- Pathogenicity in fungi often involves specific secreted proteins.
- Hydrophobins are a class of fungal proteins known for their role in surface interactions.
Purpose of the Study:
- To investigate the role of the MPG1 gene in the pathogenicity of Magnaporthe grisea.
- To characterize the protein product of MPG1 and its function in infection-related development.
Main Methods:
- Random ascospore analysis and genetic complementation were used to assess MPG1 function.
- Ultrastructural studies examined the effect of MPG1 on conidia.
- Biochemical approaches were employed to characterize the MPG1 protein.
Main Results:
- MPG1 is essential for Magnaporthe grisea's infection-related development on rice.
- The MPG1 gene product is a class I hydrophobin, directing the formation of a rodlet layer on conidia.
- This rodlet layer contributes to conidial surface hydrophobicity and pathogenicity.
Conclusions:
- MPG1 is a key pathogenicity factor in Magnaporthe grisea.
- The hydrophobin MPG1 plays a critical role in fungal development and host interaction.
- Understanding MPG1 function offers potential targets for controlling rice blast disease.