Arabidopsis Transmembrane Receptor-Like Kinases (RLKs): A Bridge between Extracellular Signal and Intracellular Regulatory Machinery

Abstract

Receptors form the crux for any biochemical signaling. Receptor-like kinases (RLKs) are conserved protein kinases in eukaryotes that establish signaling circuits to transduce information from outer plant cell membrane to the nucleus of plant cells, eventually activating processes directing growth, development, stress responses, and disease resistance. Plant RLKs share considerable homology with the receptor tyrosine kinases (RTKs) of the animal system, differing at the site of phosphorylation. Typically, RLKs have a membrane-localization signal in the amino-terminal, followed by an extracellular ligand-binding domain, a solitary membrane-spanning domain, and a cytoplasmic kinase domain. The functional characterization of ligand-binding domains of the various RLKs has demonstrated their essential role in the perception of extracellular stimuli, while its cytosolic kinase domain is usually confined to the phosphorylation of their substrates to control downstream regulatory machinery. Identification of the several ligands of RLKs, as well as a few of its immediate substrates have predominantly contributed to a better understanding of the fundamental signaling mechanisms. In the model plant Arabidopsis, several studies have indicated that multiple RLKs are involved in modulating various types of physiological roles via diverse signaling routes. Here, we summarize recent advances and provide an updated overview of transmembrane RLKs in Arabidopsis.

Moonlighting Proteins Shine New Light on Molecular Signaling Niches

“…Animals can escape these challenges but plants due to their sessile nature need to withstand or tolerate them [ 46 , 64 , 65 , 66 , 68 , 70 ]. Plant RLK diversification has resulted in great variation in the extracellular domain that contributes to their diverse roles mediating all aspects of plant growth and development and responses to the environment, notably to biotic stresses (for reviews, see for instance: [ 65 , 71 , 72 , 73 ]). Many plant RLKs bind endogenous peptide ligands such as phytosulfokine [ 74 , 75 ] or pathogen associated molecular patterns (PAMPs) and damage associated molecular patterns (DAMPs) [ 73 , 76 ].…”

Transcriptomic Profiling of Populus Roots Challenged with Fusarium Reveals Differential Responsive Patterns of Invertase and Invertase Inhibitor-Like Families within Carbohydrate Metabolism

“…Some representative types are comprised of the G/S- locus lectin receptor-like kinases (LecRLKs), wall-associated kinases (WAKs), extensin-like, self-incompatibility domain (S-domain), cysteine-rich repeat secreted proteins (CRRSPs), thaumatin-like proteins (TLPs), leaf rust kinase-likes (LRKs), and other unknown receptor kinases. A few of them exerting essential roles in plant innate immunity have been unraveled [ 55 ]. A total of 379 LRR-RLKs and 231 LecRLKs genes have been identified in the Populus genome based on the genome-wide survey [ 56 , 57 ].…”

An Ancestry Perspective of the Evolution of PBS1 Proteins in Plants

“…RLKs are present in all Viridiplantae (Streptophytes and Chlorophytes), share several typical kinase subdomains, and are induced by abiotic and biotic stress [23,24]. The proteins involved in the defense response tend to be more diverse than those involved in growth and development [25]. RLCKs, a subgroup of RLKs, belong to the RLK/Pelle family and are clustered in the superfamily of eukaryotic serine/threonine/tyrosine kinases [8].…”