Regulation of immune receptor kinases plasma membrane nanoscale landscape by a plant peptide hormone and its receptors

Abstract

Cell surface receptors survey and relay information to ensure the development and survival of multicellular organisms. In the model plant Arabidopsis thaliana, the Catharanthus roseus RLK1-like receptor kinase FERONIA (FER) regulates myriad of biological processes to coordinate development, growth and responses to the environment. We recently showed that FER positively regulates immune signaling by controlling the ligand-induced complex formation between the leucine-rich repeat receptor kinase (LRR-RK) FLAGELLIN SENSING 2 (FLS2) and its co-receptor BRASSINOSTEROID INSENSITIVE 1-ASSOCIATED KINASE 1/SOMATIC EMBRYOGENESIS RECEPTOR KINASE 3 (BAK1/SERK3). In this context, FER function is inhibited by binding of its peptide ligand RAPID ALKALINIZATION FACTOR 23 (RALF23). However, the mechanisms by which FER regulates FLS2-BAK1 complex formation remain unclear. Here, we show that FER-dependent regulation of immune signaling is independent of its kinase activity, indicating that FER rather plays a structural role. FER has been proposed to bind directly to the plant cell wall, but we found that a FER mutant unable to bind pectin is still functional in regulating immune signaling. Instead, FER- and cell wall-associated LEUCINE RICH REPEAT-EXTENSIN proteins are required for this regulation. Using high-resolution live-imaging and single-particle tracking, we observed that FER regulates FLS2 plasma membrane nanoscale dynamics, which may explain its role in controlling ligand-induced FLS2-BAK1 association. We propose that FER acts as an anchoring point connecting cell wall and plasma membrane nano-environments to enable the nucleation of pre-formed receptor/co-receptor complexes at the cell surface.

Salicylic acid regulates PIN2 auxin transporter hyperclustering and root gravitropic growth via Remorin‐dependent lipid nanodomain organisation in Arabidopsis thaliana

“…Steroid hormone brassinosteroid (BR) promotes the partitioning of the BR receptor Brassinosteroid Insensitive 1 (BRI1) to membrane nanodomains that in turn stimulates BRI1 internalisation in response to BR (Wang et al ., 2015). The modulation of the nanoclustering of receptor Flagellin Sensing 2 (FLS2) on the plant cell surface fine tunes the flagellum‐mediated innate immune responses under different conditions during plant–bacteria communication (Cui et al ., 2018; Gronnier et al ., 2020; Tran et al ., 2020). Despite both immune receptor FLS2 and the growth receptor BRI1 forming nanoclusters on the cell surface, they distribute within distinct nanodomains, suggesting a spatial separation within the PM when responding to developmental or defence signals (Bucherl et al ., 2017).…”

A hetero-oligomeric remorin-receptor complex regulates plant development

“…Images time series were recorded at 10 frames per second (100 ms exposure time). To analyze single particle tracking experiments, we used the plugin TrackMate 2.7.4 (Tinevez et al, 2016) in Fiji (Schindelin et al, 2012) as previously described (Gronnier et al, 2020).…”

“…PM functionality depends on multiprotein entities that can form higher order assemblies in the nanometer (nanodomains) or micrometer (microdomains) range (Ott, 2017; Jaillais and Ott, 2019). Among others, membrane-resident receptors have been reported to localizes to such nanodomains ((Haney et al, 2011; Bücherl et al, 2017; Burkart and Stahl, 2017; Liang et al, 2018; Gronnier et al, 2020)). Using fluorescently-tagged fusion proteins, membrane nanodomains appear as punctate structures at the cell surface with a low degree of lateral mobility (Ott, 2017).…”

Molecular mechanisms of early plant pattern-triggered immune signaling

“…Mammalian RTKs also localize to specific plasma membrane nanodomains, which can be arranged in a polar manner across the cell (Gao et al, 2015). Cell biological work has now shown that plant RKs also localize to distinct nanodomains within the plasma membrane, which may facilitate pathway-specific signaling (B€ ucherl et al, 2017;Gronnier et al, 2020). However, the nature and stoichiometry of these nanodomains remains to be definitively resolved.…”