title: Independent S-locus mutations caused self-fertility in Arabidopsis thaliana.
abstract: A common yet poorly understood evolutionary transition among flowering plants is a switch from outbreeding to an inbreeding mode of mating. The model plant Arabidopsis thaliana evolved to an inbreeding state through the loss of self-incompatibility, a pollen-rejection system in which pollen recognition by the stigma is determined by tightly linked and co-evolving alleles of the S-locus receptor kinase (SRK) and its S-locus cysteine-rich ligand (SCR). Transformation of A. thaliana, with a functional AlSRKb-SCRb gene pair from its outcrossing relative A. lyrata, demonstrated that A. thaliana accessions harbor different sets of cryptic self-fertility-promoting mutations, not only in S-locus genes, but also in other loci required for self-incompatibility. However, it is still not known how many times and in what manner the switch to self-fertility occurred in the A. thaliana lineage. Here, we report on our identification of four accessions that are reverted to full self-incompatibility by transformation with AlSRKb-SCRb, bringing to five the number of accessions in which self-fertility is due to, and was likely caused by, S-locus inactivation. Analysis of S-haplotype organization reveals that inter-haplotypic recombination events, rearrangements, and deletions have restructured the S locus and its genes in these accessions. We also perform a Quantitative Trait Loci (QTL) analysis to identify modifier loci associated with self-fertility in the Col-0 reference accession, which cannot be reverted to full self-incompatibility. Our results indicate that the transition to inbreeding occurred by at least two, and possibly more, independent S-locus mutations, and identify a novel unstable modifier locus that contributes to self-fertility in Col-0.
authors.affiliation: Department of Plant Biology, Cornell University, Ithaca, NY, USA.
authors.forename: Nathan A
authors.initials: NA
authors.lastname: Boggs
authors.forename: June B
authors.initials: JB
authors.lastname: Nasrallah
authors.forename: Mikhail E
authors.initials: ME
authors.lastname: Nasrallah
mesh_terms: D017360:Arabidopsis / Q000235:genetics*; D005075:Biological Evolution; D005298:Fertility / Q000235:genetics*; D006239:Haplotypes; D009154:Mutation; D010940:Plant Proteins / Q000235:genetics*; D011494:Protein Kinases / Q000235:genetics*; D040641:Quantitative Trait Loci; D011995:Recombination, Genetic
chemical_list: D010940:Plant Proteins; D011494:Protein Kinases; C079832:S-receptor kinase