An update on evolutionary, structural, and functional studies of receptor-like kinases in plants

Abstract

All living organisms must develop mechanisms to cope with and adapt to new environments. The transition of plants from aquatic to terrestrial environment provided new opportunities for them to exploit additional resources but made them vulnerable to harsh and ever-changing conditions. As such, the transmembrane receptor-like kinases (RLKs) have been extensively duplicated and expanded in land plants, increasing the number of RLKs in the advanced angiosperms, thus becoming one of the largest protein families in eukaryotes. The basic structure of the RLKs consists of a variable extracellular domain (ECD), a transmembrane domain (TM), and a conserved kinase domain (KD). Their variable ECDs can perceive various kinds of ligands that activate the conserved KD through a series of auto- and trans-phosphorylation events, allowing the KDs to keep the conserved kinase activities as a molecular switch that stabilizes their intracellular signaling cascades, possibly maintaining cellular homeostasis as their advantages in different environmental conditions. The RLK signaling mechanisms may require a coreceptor and other interactors, which ultimately leads to the control of various functions of growth and development, fertilization, and immunity. Therefore, the identification of new signaling mechanisms might offer a unique insight into the regulatory mechanism of RLKs in plant development and adaptations. Here, we give an overview update of recent advances in RLKs and their signaling mechanisms.

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“…RLKs play diverse roles in plant signaling, influencing defense responses, hormone perception, and development. They mediate extracellular signals, regulating growth, immunity, and environmental adaptation [51,[57][58][59]. Recent research highlights their involvement in complex signaling networks, interacting with other proteins dynamically [57].…”

“…They mediate extracellular signals, regulating growth, immunity, and environmental adaptation [51,[57][58][59]. Recent research highlights their involvement in complex signaling networks, interacting with other proteins dynamically [57]. Understanding RLK-mediated pathways is crucial for enhancing crop performance amid changing conditions.…”

“…Understanding RLK-mediated pathways is crucial for enhancing crop performance amid changing conditions. Some RLKs share signaling cascades, like BRI1, EMS1, and NILR1, suggesting intricate signaling mechanisms [4,39,51,57]. Advanced techniques such as domain swapping and single-cell omics analysis can deepen our understanding of RLK pathways with precision.…”

“…Functional redundancy among RLKs complicates their identification; for instance, BAK1 serves as a co-receptor for BRI1 and regulates immune responses through FLS2 and EFR pathways. Advanced methods like CRISPR and sophisticated phenotypic analysis can address this redundancy [4,57].…”

“…Liu et al [57] studied the effects of homobrassinolide (HBR) on barley root growth and observed enhanced mitotic activity and significant root tip enlargement compared to the control group.…”