Heterogeneous evolutionary processes affect R gene diversity in natural populations of Solanum pimpinellifolium
- 6 December 2004
- journal article
- Published by Proceedings of the National Academy of Sciences in Proceedings of the National Academy of Sciences
- Vol. 101 (50) , 17444-17449
- https://doi.org/10.1073/pnas.0407899101
Abstract
Resistance (R) genes of plants are responsible for pathogen recognition and encode proteins that trigger a cascade of responses when a pathogen invades a plant. R genes are assumed to be under strong selection, but there is limited knowledge of the processes affecting R gene diversity in the wild. In this study, DNA sequence variation of Cf-2 homologs was surveyed in populations of Solanum pimpinellifolium, a wild relative of the cultivated tomato. The Cf-2 locus is involved in resistance to strains of the fungus Cladosporium fulvum. At least 26 different Cf-2 homologs were detected in natural populations of S. pimpinellifolium. These homologs differ by single base pair substitutions as well as indels in regions coding for leucine-rich repeats. Molecular population genetic analyses suggest that natural selection has acted heterogeneously on Cf-2 homologs, with selection against amino acid substitutions occurring in the 5' portion of the genes, and possible restricted positive selection in the 3' end. Balancing selection may have maintained haplotypes at the 5' end of the genes. Limited sequence exchange between genes has also contributed to sequence variation. S. pimpinellifolium individuals differ in the number of Cf-2 homologs they contain, obscuring the relationships of orthology and paralogy. This survey of Cf-2 variation in S. pimpinellifolium illustrates the wealth of R gene diversity that exists in wild plant populations, as well as the complexity of interacting genetic and evolutionary processes that generate such diversity.Keywords
This publication has 51 references indexed in Scilit:
- Population structure and phylogeography ofSolanum pimpinellifoliuminferred from a nuclear geneMolecular Ecology, 2004
- Evolutionary dynamics of an Arabidopsis insect resistance quantitative trait locusProceedings of the National Academy of Sciences, 2003
- Variable leucine‐rich repeats of tomato disease resistance genes Cf‐2 and Cf‐5 determine specificityMolecular Plant Pathology, 2003
- The leucine-rich repeat as a protein recognition motifPublished by Elsevier ,2001
- Ancient Diversification of the Pto Kinase Family Preceded Speciation in SolanumMolecular Plant-Microbe Interactions®, 2001
- The C-terminal Dilysine Motif for Targeting to the Endoplasmic Reticulum Is Not Required for Cf-9 FunctionMolecular Plant-Microbe Interactions®, 2001
- Domain Swapping and Gene Shuffling Identify Sequences Required for Induction of an Avr-Dependent Hypersensitive Response by the Tomato Cf-4 and Cf-9 ProteinsPlant Cell, 2001
- DnaSP version 3: an integrated program for molecular population genetics and molecular evolution analysis.Bioinformatics, 1999
- The Tomato Cf-5 Disease Resistance Gene and Six Homologs Show Pronounced Allelic Variation in Leucine-Rich Repeat Copy NumberPlant Cell, 1998
- Genetic variation inLycopersicon pimpinellifolium: Evidence of evolutionary change in mating systemsÖsterreichische botanische Zeitschrift, 1977