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Zusammenfassung:
The maintenance of allelic diversity at loci encoding components of the non-self recognition system is expected to be evolutionarily favorable because it allows individuals within a species to recognize and defend themselves against a broad range of pathogens. However, such diversity can also inadvertently lead to the formation of reproductive barriers, as was observed for an intraspecific cross between the Uk-1 and Uk-3 accessions of Arabidopsis thaliana. The F1 hybrid progeny exhibited a constitutively active pathogen defense response that led to reproductive failure during growth at the ecologically relevant temperature of 16°C. This incompatibility, known as hybrid necrosis, was due to an epistatic interaction between two loci associated with the pathogen defense response, suggesting that diversification of pathogen recognition loci could result in the restriction of gene flow among individuals within a species. his restriction could be reinforced or overcome, however, by the presence of alleles at additional loci that enhance or suppress deleterious hybrid phenotypes. Here, we report that the Er-0, Hl-0, Dr-0, and Is-0 accessions of A. thaliana carry dominant suppressors of the Uk-1/Uk-3 hybrid necrosis, while dominant enhancers are carried by the Bur-0 and Jl-2 accessions. Using high-throughput sequencing of pooled individuals with a complex genetic make-up, we mapped the Er-0 suppressor to a roughly 500-kb interval on chromosome 5. Ongoing work towards identifying the genes that modify hybrid necrosis will provide insight into the evolutionary forces that lead to reproductive isolation and may uncover novel components of the plant defense response mechanism.
