Distinct resistance genes arrest development of the oomycete rust Albugo candida in Arabidopsis thaliana at different infection stages
V. CEVIK (1), S. Huh (1), A. Cooper (2), O. Furzer (1), S. Fairhead (3), J. Taylor (2), J. Carlier (4), P. Sarris (5), J. Jones (1), E. Holub (2) (1) The Sainsbury Laboratory, United Kingdom; (2) University of Warwick, School of Life Sciences, Warwick Crop Centre, United Kingdom; (3) University of Warwick, School of Life Sciences, Warwick Crop Centre, United Kingdom; (4) University of Algarve, Laboratory of Genomics and Genetic Improvement, Portugal; (5) Division of Plant and Microbial Sciences, School of Biosciences, University of Exeter, United Kingdom

The biotrophic oomycete Albugo candida causes white rust disease in many Brassicaceae species. Some A. candida races can also infect various Arabidopsis accessions.  This provides an excellent experimental pathosystem for molecular dissection of defense at different stages of rust development.  The Arabidopsis accession Col-0 allele of the TIR-NB-LRR (TNL) protein encoding gene WRR4 confers an early, full immunity to multiple races of A. candida. Further genetic analysis showed that WRR4-mediated immunity is epistatic to additional resistance genes in Col-0 that confer chlorotic and necrotic resistance phenotypes.  Both phenotypes are associated with colonization of mesophyll, but the parasite does not reproduce. The chlorotic resistance phenotype requires Col-0 alleles of paired TIR-NB-LRR genes (WRR5A and WRR5B) to confer resistance to A. candida.  Interestingly, WRR5B encodes a TNL protein with non-canonical domain architecture.  It contains a C-terminal zinc-binding LIM (Lin-11,Isl-1,Mec-3) domain and was previously implicated in cold stress and defense response (CHS3). The WRR5A encodes a typical TNL protein and was previously implicated in shade avoidance (CSA1). We also cloned the gene (WRR7) that provides necrotic resistance phenotype. The WRR7 gene codes for CC-NB-LIM type of resistance protein.  Based on the ‘Integrated Decoy’ model, our results indicate that LIM domain present both in WRR5B and WRR7 may mimic the effector substrate property of the original target in the host cell, enabling the detection of the pathogen. 

Abstract Number: P17-505
Session Type: Poster