Ligand-Induced Receptor-like Kinase Complex Regulates Floral Organ Abscission in Arabidopsis

•The SERK family receptor-like kinases redundantly regulate floral organ abscission•SERKs act downstream of the IDA ligand and upstream of a MAPK cascade•SERKs associate with the HAE and HSL2 receptors in a ligand-induced manner•SERK3 and HAE transphosphorylate each other in their cytosolic domains

SummaryAbscission is a developmental process that enables plants to shed unwanted organs. In Arabidopsis, the floral organ abscission is regulated by a signaling pathway consisting of the peptide ligand IDA, the receptor-like kinases (RLKs) HAE and HSL2, and a downstream MAP kinase (MAPK) cascade. However, little is known about the molecular link between ligand-receptor pairs and intracellular signaling. Here, we report that the SERK family RLKs function redundantly in regulating floral organ abscission downstream of IDA and upstream of the MAPK cascade. IDA induces heterodimerization of HAE/HSL2 and SERKs, which transphosphorylate each other. The SERK3 residues mediating its interaction with the immune receptor FLS2 and the brassinosteroid receptor BRI1 are also required for IDA-induced HAE/HSL2-SERK3 interaction, suggesting SERKs serve as co-receptors of HAE/HSL2 in perceiving IDA. Thus, our study reveals the signaling activation mechanism in floral organ abscission by IDA-induced HAE/HSL2-SERK complex formation accompanied by transphosphorylation.

Graphical AbstractFigure optionsDownload full-size imageDownload as PowerPoint slide