An RLP23–SOBIR1–BAK1 complex mediates NLP-triggered immunity

Abstract

Plants and animals employ innate immune systems to cope with microbial infection. Pattern-triggered immunity relies on the recognition of microbe-derived patterns by pattern recognition receptors (PRRs). Necrosis and ethylene-inducing peptide 1-like proteins (NLPs) constitute plant immunogenic patterns that are unique, as these proteins are produced by multiple prokaryotic (bacterial) and eukaryotic (fungal, oomycete) species. Here we show that the leucine-rich repeat receptor protein (LRR-RP) RLP23 binds in vivo to a conserved 20-amino-acid fragment found in most NLPs (nlp20), thereby mediating immune activation in Arabidopsis thaliana. RLP23 forms a constitutive, ligand-independent complex with the LRR receptor kinase (LRR-RK) SOBIR1 (Suppressor of Brassinosteroid insensitive 1 (BRI1)-associated kinase (BAK1)-interacting receptor kinase 1), and recruits a second LRR-RK, BAK1, into a tripartite complex upon ligand binding. Stable, ectopic expression of RLP23 in potato (Solanum tuberosum) confers nlp20 pattern recognition and enhanced immunity to destructive oomycete and fungal plant pathogens, such as Phytophthora infestans and Sclerotinia sclerotiorum. PRRs that recognize widespread microbial patterns might be particularly suited for engineering immunity in crop plants.

Techniques for the analysis of protein-protein interactions in vivo

“…6B; Grefen and Blatt, 2012a). This ratiometric BiFC system has been utilized successfully by a number of different laboratories with a diverse range of PPIs (Karnik et al, 2013b;Lipka et al, 2014;Albert et al, 2015;Kumar et al, 2015;Le et al, 2016;Perrella et al, 2016).…”

“…Additionally, an interaction in CoIP could be due to the presence of a protein complex of multiple interactors, with an apparent binary interaction facilitated by known or unknown cofactors (Hall, 2005). This comes as a blessing in disguise, as it allows higher order protein complexes or ligand-induced dimerization to be dissected, a phenomenon that is neatly exploited when an interaction between two POIs is either induced by an exogenously applied factor (ligand, pathogen, and so on) or disrupted in a knockout line of the endogenous bridging factor (Chinchilla et al, 2007;Albert et al, 2015;Fuchs et al, 2016) Recently, two novel techniques have been developed that circumvent the limitations of traditional CoIP. Both developments, single-molecule pull down (Jain et al, 2011) and real-time single-molecule CoIP (Lee et al, 2013), use total internal reflection microscopy (Axelrod, 2001) to detect interactions on a coverslip.…”

New insights into receptor-like protein functions in Arabidopsis

“…It has been demonstrated that SOBIR1 physically interacted with Cf-4, Ve1, LepR3, Rlm2, AtRLP1, AtRLP23, AtRLP30 and AtRLP42, and was required for the proper function of these RLPs. 9,10,12,13,15,16,[24][25][26] However, it is unclear about the biological relevance of the physical interaction between SOBIR1 and two developmental RLPs CLV2 and TMM, respectively. It could postulate that SOBIR1 may involve in the CLV2-and/or TMM-mediated developmental processes.…”

“…11,12 Although the biological functions of most AtRLP genes still remain unknown, a number of AtRLP genes have been assigned functions. In addition to CLV2 and TMM, the functionally characterized AtRLP proteins comprise AtRLP1/ReMAX that mediates recognition of eMAX, 13 AtRLP3/RFO that involves in resistance to the vascular wilt fungus Fusarium oxysporum, 14 AtRLP23 that perceives a conserved fragment present in most necrosis and ethyleneinducing peptide (NEP) 1-like proteins and subsequently activate the immunity, 15 AtRLP30 that implicates in resistance against Pseudomonas syringae pv. phaseolicola, 12 AtRLP42/ RBPG1 that confers resistance to endopolygalacturonases, 16 AtRLP44 that activates brassinosteroid signaling through interaction BAK1, 17 and AtRLP51/SNC2 and AtRLP55 that implicate in basal defense against the bacterial pathogen Pseudomonas syringae pv tomato DC3000.…”

“…1 Nevertheless, the generation of gain-of-function mutants has produced invaluable information on the function of AtRLP genes such as TMM, Ve1, AtRLP23 and AtRLP44. 6,15,17,21 We thus performed a genome-wide functional analysis of AtRLP genes using overexpression analysis to gain additional insights into their potential roles in various aspects such as Arabidopsis growth and development, and salt tolerance. 20 Despite the absence of any phenotypic alterations under normal growth condition, the overexpression of AtRLP3 and AtRLP11 could rescue the clv2-1 mutant.…”