Grant, Murray, McDowell, J. M., Sharpe, A. G., de Torres Zabala, M., Lydiate, D. J. and Dangl, J. L. (1998) Independent deletions of a pathogen-resistance gene in Brassica and Arabidopsis. Proceedings of the National Academy of Sciences of the United States of America, 95 (26). pp. 15843-15848. doi:10.1073/pnas.95.26.15843 ISSN 0027-8424.

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Abstract

Plant disease resistance (R) genes confer race-specific resistance to pathogens and are genetically defined on the basis of intra-specific functional polymorphism. Little is known about the evolutionary mechanisms that generate this polymorphism. Most R loci examined to date contain alternate alleles and/or linked homologs even in disease-susceptible plant genotypes. In contrast, the resistance to Pseudomonas syringae pathovar maculicola (RPM1) bacterial resistance gene is completely absent (rpm1-null) in 5/5 Arabidopsis thaliana accessions that lack RPM1 function. The rpm1-null locus contains a 98-bp segment of unknown origin in place of the RPM1 gene. We undertook comparative mapping of RPM1 and flanking genes in Brassica napus to determine the ancestral state of the RPM1 locus. We cloned two B. napus RPM1 homologs encoding hypothetical proteins with ≈81% amino acid identity to Arabidopsis RPM1. Collinearity of genes flanking RPM1 is conserved between B. napus and Arabidopsis. Surprisingly, we found four additional B. napus loci in which the flanking marker synteny is maintained but RPM1 is absent. These B. napus rpm1-null loci have no detectable nucleotide similarity to the Arabidopsis rpm1-null allele. We conclude that RPM1 evolved before the divergence of the Brassicaceae and has been deleted independently in the Brassica and Arabidopsis lineages. These results suggest that functional polymorphism at R gene loci can arise from gene deletions.

Item Type:	Journal Article
Divisions:	Faculty of Science, Engineering and Medicine > Science > Life Sciences (2010- )
Journal or Publication Title:	Proceedings of the National Academy of Sciences of the United States of America
Publisher:	National Academy of Sciences
ISSN:	0027-8424
Official Date:	1998
Dates:	Date Event 1998 UNSPECIFIED
Volume:	95
Number:	26
Page Range:	pp. 15843-15848
DOI:	10.1073/pnas.95.26.15843
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access

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