Epistasis, the spice of life: Lessons from the study of the plant immune system

My group is addressing fundamental questions in evolutionary biology, using both genome- and phenotype-first approaches. A few years ago, we discovered that Arabidopsis thaliana is a great model for the study of hybrid necrosis. This widespread syndrome of hybrid failure in plants is caused by plant paranoia – regardless of the presence of enemies, plants “think” they are being attacked by pathogens. Over the past decade, we have studied in detail the underlying genetics, finding that often one or two loci encoding NLR immune receptors are causal. NLRs make up the most variable gene family in plants, and it is not surprising that they are often involved in genome-genome conflicts. Hybrid necrosis results when NLR genes meet that have not been co-adapted. I will describe how our unique lens for the plant immune system has led to insights that were not obtained with conventional laboratory genetics. Our goal for the next decade is to understand the genomic and geographic patterns of immune system diversity. Last year, we initiated a project, Pathodopsis in which we aim to describe genetic diversity in the host and two important pathogens, the generalist Pseudomonas and the specialist Hyaloperonospora arabidopsidis. The long-term vision is to produce maps of resistance alleles in the host, and of effector alleles in the pathogens, in order to learn who normally wins in a wild plant pathosystem – the host or the pathogen