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. 2020 Dec;104(5):1369-1381.
doi: 10.1111/tpj.15006. Epub 2020 Oct 23.

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  1 , Lorena Pizarro  1 , Silvia Schuster  1 , Adi Avni  1
Affiliations

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 et al. Plant J. 2020 Dec.

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.

Keywords: malectin-like domain; pattern recognition receptor; plant immunity receptor-like kinase; receptor-like protein.

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References

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