Using structure-guided sequence analysis we uncover previously uncharacterized CIF peptides conserved among higher plants.Quantitative binding assays with known and novel CIFs suggest that the homologous LRR-RKs GSO1/SGN3 and GSO2 have evolved unique peptide binding properties to control different developmental processes.A quantitative biochemical interaction screen, a CIF peptide antagonist and genetic analyses together implicate SERK proteins as essential coreceptor kinases required for GSO1/SGN3 and GSO2 receptor activation.
Our work provides a mechanistic framework for the recognition of sequence-divergent peptide hormones in plants.
Plants use leucine-rich repeat receptor kinases (LRR-RKs) to sense sequence diverse peptide hormones at the cell surface.A 3.0-Å crystal structure of the LRR-RK GSO1/SGN3 regulating Casparian strip formation in the endodermis reveals a large spiral-shaped ectodomain.The domain provides a binding platform for 21 amino acid CIF peptide ligands, which are tyrosine sulfated by the tyrosylprotein sulfotransferase TPST/SGN2.GSO1/SGN3 harbors a binding pocket for sulfotyrosine and makes extended backbone interactions with CIF2.
Quantitative biochemical comparisons reveal that GSO1/SGN3–CIF2 represents one of the strongest receptor–ligand pairs known in plants.Multiple missense mutations are required to block CIF2 binding in vitro and GSO1/SGN3 function in vivo.
Using structure-guided sequence analysis we uncover previously uncharacterized CIF peptides conserved among higher plants.Quantitative binding assays with known and novel CIFs suggest that the homologous LRR-RKs GSO1/SGN3 and GSO2 have evolved unique peptide binding properties to control different developmental processes.A quantitative biochemical interaction screen, a CIF peptide antagonist and genetic analyses together implicate SERK proteins as essential coreceptor kinases required for GSO1/SGN3 and GSO2 receptor activation.
Our work provides a mechanistic framework for the recognition of sequence-divergent peptide hormones in plants.
