SlRLK-like is a malectin-like domain protein affecting localization and abundance of LeEIX2 receptor resulting in suppression of EIX-induced immune responses

Orian Sussholz, Lorena Pizarro, Silvia Schuster, Adi Avni*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

The first line of plant defense occurs when a plant pattern recognition receptor (PRR) recognizes microbe-associated molecular patterns. Plant PRRs are either receptor-like kinases (RLKs), which have an extracellular domain for ligand binding, a single-pass transmembrane domain, and an intracellular kinase domain for activating downstream signaling, or receptor-like proteins (RLPs), which share the same overall structure but lack an intracellular kinase domain. The tomato (Solanum lycopersicum) LeEIX2 is an RLP that binds ethylene-inducing xylanase (EIX), a fungal elicitor. To identify LeEIX2 receptor interactors, we conducted a yeast two-hybrid screen and found a tomato protein that we termed SlRLK-like. The interaction of LeEIX2 with SlRLK-like was verified using co-immunoprecipitation and bimolecular fluorescence complementation assays. The defense responses induced by EIX were markedly reduced when SlRLK-like was overexpressed in Nicotiana benthamiana or Nicotiana tabacum, and knockout of SlRLK-like using the CRISPR/Cas9 system increased EIX-induced ethylene production and 1-aminocyclopropane-1-carboxylate synthase (SlACS2) gene expression in tomato. Co-expression of SlRLK-like with LeEIX2 led to a reduction in its abundance, apparently through an endoplasmic reticulum-associated degradation process. Notably, truncation of SlRLK-like protein revealed that the malectin-like domain is sufficient and essential for its function. Moreover, SlRLK-like associated with the RLK FLS2, resulting in its degradation and concomitantly a reduction of the flagellin 22 (flg22)-induced burst of reactive oxygen species. In addition, SlRLK-like co-expression with other RLPs, Ve1 and AtRLP23, also led to a reduction in their abundance. Our findings suggest that SlRLK-like leads to a decreased stability of various PRRs, leading to a reduction in their abundance and resulting in attenuation of defense responses.

Original languageEnglish
Pages (from-to)1369-1381
Number of pages13
JournalPlant Journal
Volume104
Issue number5
DOIs
StatePublished - Dec 2020

Funding

FundersFunder number
Department of Life Sciences
United States - Israel Binational Agricultural Research and Development Fund
Imperial College London
United States-Israel Binational Science Foundation2013227
Israel Academy of Sciences and Humanities550/18, IS‐4842‐15 R
Israel Science Foundation
Ministry of Agriculture and Rural Development13‐37‐0001

    Keywords

    • malectin-like domain
    • pattern recognition receptor
    • plant immunity receptor-like kinase
    • receptor-like protein

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