Receptor-like kinases (RLKs) are the most important protein kinases in plants that sense environmental signals, similar to how G protein-coupled receptors (GPCRs) function in animals. Throughout the plant life cycle, RLKs play pivotal roles in the regulation of diverse biological processes, including growth, development, and response to stress stimuli, helping plants adapt to challenging habitats. The RLK family composes Receptor Kinases (RKs) and Receptor-like Cytoplasmic Kinases (RLCKs). A typical RK in plant is structured with an extracellular domain (ECD), a hydrophobic transmembrane domain (TM), and a cytoplasmic kinase domain (KD). The ECD perceives external stimuli, and the signal is transduced along the TM region, activating the cytoplasmic KD to phosphorylate substrate. This event can induce protein complex formation or position proteins correctly.

Since the discovery of the first RLK in 1990, research on RLKs has primarily focused on specific RLKs and RLCKs. While a limited number of RLKs in model plants have been annotated, functional clues are even scarcer for non-model plants. Herein, we have established the metaRLK database, offering a comprehensive characterization and cataloging of RLKs from 528 plant genomes across seven plant groups. We have formulated a coherent gene nomenclature (PENGUIN) and a topology classification that elucidates the topology distinctions between RK and RLCK, including the presence or absence of ECDs and the presence and location of Leucine-Rich Repeats (LRR). Furthermore, metaRLK provides a valuable framework for annotating data from RLK experimental assays, elucidating RLK functions and regulation. The database also incorporates search tools using Gene ID, Species ID, Gene Name, and Uniprot ID, facilitating researchers in locating RLKs relevant to their research interests.