Mutations Suppressing Immune Hybrid Incompatibility and Their Effects on Disease Resistance.

Genetic divergence between populations can lead to reproductive isolation. Hybrid incompatibilities (HI) represent intermediate points along a continuum toward speciation. In plants, genetic variation in disease resistance () genes underlies several cases of HI. The progeny of a cross between Arabidopsis () accessions Landsberg (L, Poland) and Kashmir2 (Kas2, central Asia) exhibits immune-related HI. This incompatibility is due to a genetic interaction between a cluster of eight ) (- genes (-) from L and central Asian alleles of a -family receptor-like kinase () from Kas2. In characterizing mutants altered in L/Kas2 HI, we mapped multiple mutations to the -like L locus. Analysis of these () mutants reveals complex, additive and epistatic interactions underlying - L locus activity. The effects of these mutations were measured on basal defense, global gene expression, primary metabolism, and disease resistance to a local isolate ( Gw) collected from Gorzów (Gw), where the Landsberg accession originated. Gene expression sectors and metabolic hallmarks identified for HI are both dependent and independent of - L members. We establish that mutations suppressing immune-related L/Kas2 HI do not compromise resistance to Gw. QTL mapping analysis of Gw resistance point to as the causal locus. This work provides insight into the complex genetic architecture of the - L locus and immune-related HI in Arabidopsis and into the contributions of - genes to HI and defense.