PT  - JOURNAL ARTICLE
AU  - Cristina A. Barragan
AU  - Rui Wu
AU  - Sang-Tae Kim
AU  - Wanyan Xi
AU  - Anette Habring
AU  - Jörg Hagmann
AU  - Anna-Lena Van de Weyer
AU  - Maricris Zaidem
AU  - William Wing Ho Ho
AU  - George Wang
AU  - Ilja Bezrukov
AU  - Detlef Weigel
AU  - Eunyoung Chae
TI  - RPW8/HR Repeats Predict NLR-dependent Hybrid Performance
AID  - 10.1101/559864
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 559864
4099  - http://biorxiv.org/content/early/2019/02/24/559864.short
4100  - http://biorxiv.org/content/early/2019/02/24/559864.full
AB  - Hybrid offspring can look very different from their parents, including having greatly increased or decreased fitness. In many plant species, conflicts between divergent elements of the immune system can cause hybrids to express autoimmunity, a generally deleterious syndrome known as hybrid necrosis. We are investigating multiple hybrid necrosis cases in Arabidopsis thaliana that are caused by allele-specific interactions between different variants at two unlinked resistance (R) gene clusters. One is the RESISTANCE TO PERONOSPORA PARASITICA 7 (RPP7) cluster, which encodes an intracellular nucleotide binding site-leucine rich repeat (NLR) immune receptors that confer strain-specific resistance to oomycetes. The other is the RESISTANCE TO POWDERY MILDEW 8 (RPW8)/HOMOLOG OF RPW8 (HR) locus, which encodes atypical resistance proteins that can confer broad-spectrum resistance to filamentous pathogens. There is extensive structural variation in the RPW8/HR cluster, both at the level of gene copy number and at the level of C-terminal protein repeats of unknown function. We demonstrate that the number of RPW8/HR repeats correlate, albeit in a complex manner, with the severity of hybrid necrosis when these alleles are combined with specific RPP7 variants. This observation suggests that gross structural differences, rather than individual amino acid polymorphisms, guide the genetic interaction between RPW8/HR and RPP7 alleles. We discuss these findings in light of the similarity of RPW8/HR proteins with pore-forming toxins, MLKL and HET-S, from mammals and fungi.