Receptor Kinase THESEUS1 Is a Rapid Alkalinization Factor 34 Receptor in Arabidopsis

Abstract

The growth of plants, like that of other walled organisms, depends on the ability of the cell wall to yield without losing its integrity. In this context, plant cells can sense the perturbation of their walls and trigger adaptive modifications in cell wall polymer interactions. Catharanthus roseus receptor-like kinase 1-like (CrRLK1L) THESEUS1 (THE1) was previously shown in Arabidopsis to trigger growth inhibition and defense responses upon perturbation of the cell wall, but so far, neither the ligand nor the role of the receptor in normal development was known. Here, we report that THE1 is a receptor for the peptide rapid alkalinization factor (RALF) 34 and that this signaling module has a role in the fine-tuning of lateral root initiation. We also show that RALF34-THE1 signaling depends, at least for some responses, on FERONIA (FER), another RALF receptor involved in a variety of processes, including immune signaling, mechanosensing, and reproduction [1]. Together, the results show that RALF34 and THE1 are part of a signaling network that integrates information on the integrity of the cell wall with the coordination of normal morphogenesis.

Function and solution structure of the Arabidopsis thaliana RALF8 peptide

“…This observation indicates that FER either directly or indirectly mediates RALF8‐induced signaling downstream events leading to root growth suppression. The involvement of FER in cellular responses to RALF isoforms other than RALF1 was also observed in previous studies of RALF4, RALF19, RALF23, and RALF34 . Further molecular, genetic, and biochemical experiments examining how different isoforms of RALFs and CrRLKs including FER interact to transmit downstream signaling are currently underway in our laboratories.…”

“…RALF peptides are shown to act as growth regulatory factors that suppress growth by receptor‐mediated rapid events involving protein phosphorylation, cytoplasmic calcium elevation, and extracellular pH alkalinization . A family of CrRLKs ( Catharanthus roseus receptor‐like kinases) consisting of 17 members in Arabidopsis is known to comprise receptors for RALF peptides, consistent with a model that CrRLKs are the receptors for RALFs. Arabidopsis knockout mutants of CrRLKs, including FERONIA receptor (FER), lack cellular responses to RALF‐induced rapid cytoplasmic calcium elevation.…”

Extracellular matrix sensing by FERONIA and Leucine‐Rich Repeat Extensins controls vacuolar expansion during cellular elongation in Arabidopsis thaliana

“…On the other hand, not only FER, but also THE1, binds to RALF peptides, proposing conserved interaction partners for CrRLK1Ls (Gonneau et al, 2018). It is similarly likely that LRX proteins also interact with a variety, if not all, CrRLK1Ls.…”

CrRLK1L receptor‐like kinases HERK1 and ANJEA are female determinants of pollen tube reception

“…Interactions between HERK1/ANJ, FER and LRE lead us to propose receptor complexes containing HERK1-LRE-FER and ANJ-LRE-FER at the filiform apparatus. Given the multiple CrRLK1L-RALF interactions identified to date [12,14,38,45], pollen tube-derived RALF signals constitute a potential candidate to induce synergid responses to pollen tube perception. As related members of the CrRLK1L family, HERK1 and ANJ have the potential to perform similar roles to FER, and as reported here control pollen tube rupture.…”