Amplification generates modular diversity at an avirulence locus in the pathogen Phytophthora

Area of Science:

• Plant Pathology
• Genomics
• Molecular Biology

Background:

• The late blight pathogen Phytophthora infestans rapidly evolves to evade plant resistance (R) genes.
• Understanding pathogen genome dynamics is crucial for managing crop diseases.

Purpose of the Study:

• To identify genome rearrangements in Phytophthora infestans associated with virulence changes.
• To pinpoint candidate genes responsible for overcoming plant R gene-mediated resistance.

Main Methods:

• Comparative genomic hybridization on microarrays (array-CGH) for genome-wide copy number variation.
• Positional cloning, cDNA-AFLP, and Affymetrix array expression profiling to identify candidate genes.
• Sequence analysis and comparison of P. infestans field isolates.

Main Results:

• Six loci with copy number variation were identified, including an amplification at the Avr3b-Avr10-Avr11 locus.
• The candidate gene pi3.4, encoding a transcription factor, showed amplification correlated with avirulence.
• Amplification of pi3.4 may generate modular diversity and facilitate novel gene assembly.

Conclusions:

• The pi3.4 gene amplification is a dynamic mechanism for Phytophthora infestans adaptation.
• This modular diversity offers a novel strategy for pathogens to adapt to environmental changes, specifically plant defenses.
• Understanding pi3.4 dynamics is key to developing durable disease resistance strategies.