Classification and Interactions of LRR Receptors and Co-receptors Within the Arabidopsis Plasma Membrane - An Overview.

Lin Xi,Xu Na Wu,Waltraud X Schulze,Max Gilbert

doi:10.3389/fpls.2019.00472

Abstract

Receptor kinases (RK) constitute the largest protein kinase family in plants. In particular, members of the leucine-rich repeat-receptor kinases (LRR-RKs) are involved in the perception of various signals at the plasma membrane. Experimental evidence over the past years revealed a conserved activation mechanism through ligand-inducible heterodimer formation: a ligand is recognized by a receptor kinase with a large extracellular domain (ECD). This ligand binding receptor directly interacts with a so-called co-receptor with a small ECD for ligand fixation and kinase activation. A large proportion of LRR-RKs is functionally still uncharacterized and the dynamic complexity of the plasma membrane makes it difficult to precisely define receptor kinase heterodimer pairs and their functions. In this review, we give an overview of the current knowledge of LRR receptor and co-receptor functions. We use ECD lengths to classify the LRR receptor kinase family and describe different interaction properties of ligand-binding receptors and their respective co-receptor from a network perspective.

Highlights

Receptor kinases (RK) form the largest phylogenetic kinase family in Arabidopsis (Shiu and Bleecker, 2003)
Based on various experimental evidence, leucine-rich repeat-receptor kinases (LRR-RKs) can mainly be grouped into either regulating plant growth and development, or being involved in plant immunity and defence (He et al, 2018; Jamieson et al, 2018)
Initiation of different signaling pathways by heteromeric interactions of ligand binding leucine-rich repeats (LRR)-RK and their respective co-receptors were especially well established by biochemical and genetics experiments on brassinosteroid receptor BRI1, phytosulfokine receptor PSKR1, the inflorescence deficient in abscission (IDA)-receptor HASEA involved in floral organ abscission, or the flagellin-receptor FLS2 (Nam and Li, 2002; Chinchilla et al, 2006; Albert and Felix, 2010; Mueller et al, 2012; Endo et al, 2014; Meng et al, 2015, 2016; Jorda et al, 2016; Song et al, 2016; Wang et al, 2016; Zhang et al, 2016c; Li et al, 2017; Hohmann et al, 2018b; Hu et al, 2018)

Summary

Introduction

Receptor kinases (RK) form the largest phylogenetic kinase family in Arabidopsis (Shiu and Bleecker, 2003). Initiation of different signaling pathways by heteromeric interactions of ligand binding LRR-RK and their respective co-receptors were especially well established by biochemical and genetics experiments on brassinosteroid receptor BRI1, phytosulfokine receptor PSKR1, the inflorescence deficient in abscission (IDA)-receptor HASEA involved in floral organ abscission, or the flagellin-receptor FLS2 (Nam and Li, 2002; Chinchilla et al, 2006; Albert and Felix, 2010; Mueller et al, 2012; Endo et al, 2014; Meng et al, 2015, 2016; Jorda et al, 2016; Song et al, 2016; Wang et al, 2016; Zhang et al, 2016c; Li et al, 2017; Hohmann et al, 2018b; Hu et al, 2018). SERKs and CIKs are the only members of the ‘co-receptor group’ with short ECD for which experimental evidence of their function as co-receptors is available (Figure 1B).

Results

Conclusion