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Conditional neutrality at two adjacent NBS‐LRR disease resistance loci in natural populations of Arabidopsis lyrata
Author(s) -
GOS GESSECA,
WRIGHT STEPHEN I
Publication year - 2008
Publication title -
molecular ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.619
H-Index - 225
eISSN - 1365-294X
pISSN - 0962-1083
DOI - 10.1111/j.1365-294x.2008.03968.x
Subject(s) - biology , genetics , balancing selection , nonsynonymous substitution , locus (genetics) , gene , outcrossing , natural selection , nucleotide diversity , single nucleotide polymorphism , population , arabidopsis , local adaptation , allele , candidate gene , genome , haplotype , genotype , mutant , ecology , pollen , demography , sociology
We examined patterns of nucleotide diversity at a genomic region containing two linked candidate disease resistance (NBS‐LRR) genes in seven populations of the outcrossing plant Arabidopsis lyrata . In comparison with two adjacent control genes and neutral reference genes across the genome, the NBS‐LRR genes exhibited elevated nonsynonymous variation and a large number of major‐effect polymorphisms causing early stop codons and/or frameshift mutations. In contrast, analysis of synonymous diversity provided no evidence that the region was subject to long‐term balancing selection or recent selective sweeps in any of the seven populations surveyed. Also in contrast with earlier surveys of one of these R genes, there was no evidence that the resistance genes or the major‐effect mutations were subject to elevated differentiation between populations. We suggest that conditional neutrality in the absence of the corresponding pathogen, rather than long‐term balancing selection or local adaptation, may in some circumstances be a significant cause of elevated functional polymorphism at R genes. In contrast with the R genes, analysis of diversity and differentiation at the flanking FERONIA locus showed high population divergence, suggesting local adaptation on this locus controlling male–female signalling during fertilization.