Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 102, Issue 21, Pages 7766-7771Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0500113102
Keywords
microsynteny; Phytophthora infestans; hypersensitive response; linkage disequilibrium; hemibiotroph
Categories
Funding
- Biotechnology and Biological Sciences Research Council [P20029] Funding Source: Medline
- Biotechnology and Biological Sciences Research Council [P20029] Funding Source: researchfish
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The oomycete Phytophthora infestans causes late blight, the potato disease that precipitated the Irish famines in 1846 and 1847. It represents a reemerging threat to potato production and is one of > 70 species that are arguably the most devastating pathogens of dicotyledonous plants. Nevertheless, little is known about the molecular bases of pathogenicity in these algae-like organisms or of avirulence molecules that are perceived by host defenses. Disease resistance alleles, products of which recognize corresponding avirullence molecules in the pathogen, have been introgressed into the cultivated potato from a wild species, Solanum demissum, and R1 and R3a have been identified. We used association genetics to identify Avr3a and show that it encodes a protein that is recognized in the host cytoplasm, where it triggers R3a-dependent cell death. Avr3a resides in a region of the P. infestans genome that is colinear with the locus containing avirulence gene ATR1(NdWsB) in Hyaloperonospora parasitica, an oomycete pathogen of Arabidopsis. Remarkably, distances between conserved genes in these avirullence loci were often similar, despite intervening genomic variation. We suggest that Avr3a has undergone gene duplication and that an allele evading recognition by R3a arose under positive selection.
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