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Evolution of plant pathogenicity in Streptomyces
Rosemary Loria1, Johan Kers, Madhumita Joshi
1Department of Plant Pathology, Cornell University, Ithaca, New York 14853-4203, USA. rl21@cornell.edu
Annual Review of Phytopathology
|May 25, 2006
Summary
Soil bacteria Streptomyces scabies cause potato scab by producing toxins like thaxtomin and proteins like Nec1. These pathogens spread via mobile genetic elements, leading to new agricultural diseases.
Area of Science:
- Microbiology
- Plant Pathology
- Genetics
Background:
- Soil-dwelling Streptomyces species include plant pathogens causing significant agricultural diseases like potato scab.
- Streptomyces scabies is a primary cause of potato scab, but other species induce similar symptoms.
- Understanding pathogen mechanisms is crucial for managing plant diseases.
Purpose of the Study:
- To investigate the molecular mechanisms underlying host manipulation by plant pathogenic Streptomyces species.
- To identify key virulence factors and their genetic basis in Streptomyces scabies.
- To elucidate the role of mobile genetic elements in the emergence of new plant pathogens.
Main Methods:
- Molecular genetic analysis of Streptomyces scabies.
- Identification and characterization of phytotoxins (thaxtomin) and necrogenic proteins (Nec1).
- Analysis of pathogenicity-associated islands (PAIs) and their mobilization via conjugation.
Main Results:
- Thaxtomin inhibits plant cellulose biosynthesis, induces Ca2+ spiking, and causes cell death.
- Nec1 contributes to virulence across various plant species.
- Thaxtomin and Nec1 genes are located on a mobilizable PAI, which integrates into the host chromosome, facilitating pathogen evolution.
Conclusions:
- Mobile genetic elements like PAIs play a critical role in the emergence and spread of plant pathogenic Streptomyces species.
- Thaxtomin and Nec1 are key virulence factors contributing to disease development.
- The availability of the S. scabies genome sequence will advance research into plant-pathogen interactions.
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