RPW8/HR repeats control NLR activation in Arabidopsis thaliana.

• Main Authors: Cristina A Barragan, Rui Wu, Sang-Tae Kim, Wanyan Xi, Anette Habring, Jörg Hagmann, Anna-Lena Van de Weyer, Maricris Zaidem, William Wing Ho Ho, George Wang, Ilja Bezrukov, Detlef Weigel, Eunyoung Chae
• Format: Article
• Language: English
• Published: Public Library of Science (PLoS) 2019-07-01
• Series: PLoS Genetics
• Online Access: https://doi.org/10.1371/journal.pgen.1008313

In many plant species, conflicts between divergent elements of the immune system, especially nucleotide-binding oligomerization domain-like receptors (NLR), can lead to hybrid necrosis. Here, we report deleterious allele-specific interactions between an NLR and a non-NLR gene cluster, resulting in not one, but multiple hybrid necrosis cases in Arabidopsis thaliana. The NLR cluster is RESISTANCE TO PERONOSPORA PARASITICA 7 (RPP7), which can confer strain-specific resistance to oomycetes. The non-NLR cluster is RESISTANCE TO POWDERY MILDEW 8 (RPW8) / HOMOLOG OF RPW8 (HR), which can confer broad-spectrum resistance to both fungi and oomycetes. RPW8/HR proteins contain at the N-terminus a potential transmembrane domain, followed by a specific coiled-coil (CC) domain that is similar to a domain found in pore-forming toxins MLKL and HET-S from mammals and fungi. C-terminal to the CC domain is a variable number of 21- or 14-amino acid repeats, reminiscent of regulatory 21-amino acid repeats in fungal HET-S. The number of repeats in different RPW8/HR proteins along with the sequence of a short C-terminal tail predicts their ability to activate immunity in combination with specific RPP7 partners. Whether a larger or smaller number of repeats is more dangerous depends on the specific RPW8/HR autoimmune risk variant.