Present address: Institute of Arable Crop Research, Rothamsted, Harpenden, Hertfordshire AL25 2JQ, UK.
RPP13 is a simple locus in Arabidopsis thaliana for alleles that specify downy mildew resistance to different avirulence determinants in Peronospora parasitica
Article first published online: 25 DEC 2001
The Plant Journal
Volume 21, Issue 2, pages 177–188, January 2000
How to Cite
Bittner-Eddy, P. D., Crute, I. R., Holub, E. B. and Beynon, J. L. (2000), RPP13 is a simple locus in Arabidopsis thaliana for alleles that specify downy mildew resistance to different avirulence determinants in Peronospora parasitica . The Plant Journal, 21: 177–188. doi: 10.1046/j.1365-313x.2000.00664.x
- Issue published online: 25 DEC 2001
- Article first published online: 25 DEC 2001
- Received 30 September 1999;revised 6 December 1999;accepted 7 December 1999.
Disease resistance (R) genes are found in plants as either simple (single allelic series) loci, or more frequently as complex loci of tandemly repeated genes. These different loci are likely to be under similar evolutionary forces from pathogens, but the contrast between them suggests important differences in mechanisms associated with DNA structure and recombination that generate and maintain R gene diversity. The RPP13 locus in Arabidopsis represents an important paradigm for studying the evolution of an R gene at a simple locus. The RPP13 allele from the accession Nd-1, designated RPP13-Nd, confers resistance to five different isolates of the biotrophic oomycete, Peronospora parasitica (causal agent of downy mildew), and encodes an NBS-LRR type R protein with a putative amino-terminal leucine zipper. The RPP13-Rld allele, cloned from the accession Rld-2, encodes a different specificity. Comparison of three RPP13 alleles revealed a high rate of amino acid divergence within the LRR domain, less than 80% identity overall, compared to the remainder of the protein (>95% identity). We also found evidence for positive selection in the LRR domain for amino acid diversification outside the core conserved β-strand/β-turn motif, suggesting that more of the LRR structure is available for interaction with target molecules than has previously been reported for other R gene products. Furthermore, an amino acid sequence (LLRVLDL) identical in an LRR among RPP13 alleles is conserved in other LZ NBS-LRR type R proteins, suggesting functional significance.