Genomic screens identify a new phytobacterial microbe-associated molecular pattern and the cognate Arabidopsis receptor-like kinase that mediates its immune elicitation

Abstract

BackgroundThe recognition of microbe-associated molecular patterns during infection is central to the mounting of an effective immune response. In spite of their importance, it remains difficult to identify these molecules and the host receptors required for their perception, ultimately limiting our understanding of the role of these molecules in the evolution of host-pathogen relationships.ResultsWe employ a comparative genomics screen to identify six new immune eliciting peptides from the phytopathogenic bacterium Pseudomonas syringae. We then perform a reverse genetic screen to identify Arabidopsis thaliana leucine-rich repeat receptor-like kinases required for the recognition of these elicitors. We test the six elicitors on 187 receptor-like kinase knock-down insertion lines using a high-throughput peroxidase-based immune assay and identify multiple lines that show decreased immune responses to specific peptides. From this primary screen data, we focused on the interaction between the xup25 peptide from a bacterial xanthine/uracil permease and the Arabidopsis receptor-like kinase xanthine/uracil permease sensing 1; a family XII protein closely related to two well-characterized receptor-like kinases. We show that xup25 treatment increases pathogenesis-related gene induction, callose deposition, seedling growth inhibition, and resistance to virulent bacteria, all in a xanthine/uracil permease sensing 1-dependent manner. Finally, we show that this kinase-like receptor can bind the xup25 peptide directly. These results identify xup25 as a P. syringae microbe-associated molecular pattern and xanthine/uracil permease sensing 1 as a receptor-like kinase that detects the xup25 epitope to activate immune responses.ConclusionsThe present study demonstrates an efficient method to identify immune elicitors and the plant receptors responsible for their perception. Further exploration of these molecules will increase our understanding of plant-pathogen interactions and the basis for host specificity.Electronic supplementary materialThe online version of this article (doi:10.1186/s13059-016-0955-7) contains supplementary material, which is available to authorized users.

Receptor Kinases in Plant-Pathogen Interactions: More Than Pattern Recognition

“…These findings directly led to the discovery of flgII-28 as a pattern recognized by LRR-RK FLS3 (see below) and Ave1 as an effector recognized by LRR-RLP Ve1 in tomato plants. Most recently, this approach was applied to identify six new peptides, including xup25, from Pseudomonas syringae that trigger immune responses in Arabidopsis (Mott et al, 2016). This important work further illustrates the power of the comparative genomics approach in revealing novel microbial patterns and in isolating their corresponding PRRs.…”

The population genetic test Tajima's D identifies genes encoding pathogen‐associated molecular patterns and other virulence‐related genes in Ralstonia solanacearum

“…Therefore, fliC probably evolves neutrally in R. solanacearum because all extant R. solanacearum fliC alleles are derived from an ancestral allele that had already evolved to escape recognition. Another P. syringae PAMP that was not flagged in our screen and for which the R. solanacearum allele was not found to trigger any ROS was Xup 25 (Mott et al ., ) (Fig. and Table ).…”

“…() and Mott et al . (), which is based on the hypothesis that PAMPs are encoded by core genome genes that are under selection to escape recognition by plant PRRs. We decided to identify core genome genes that do not evolve neutrally by calculating Tajima's D , which is a measure of deviation from neutral evolution (Tajima, ).…”

Pattern Recognition Receptors—Versatile Genetic Tools for Engineering Broad-Spectrum Disease Resistance in Crops

“…Furthermore, the identification of various PRRs for chemically diverse types of MAMPs has revealed that plant PRRs are typically RLKs or RLPs. Thus, these protein families can now also be systematically tested for a putative role in plant immunity, for instance through screening for altered resistance against the pathogen of interest in loss-or gain-of-function mutants or natural accessions, or through heterologous expression in suitable model plants (e.g., Arabidopsis thaliana or N. benthamiana) [64][65][66][67][68][69].…”