Molecular mechanism for the recognition of sequence-divergent CIF peptides by the plant receptor kinases GSO1/SGN3 and GSO2

Abstract

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 novel 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 LRR-RKs as essential co-receptor kinases required for GSO1/SGN3 and GSO2 receptor activation. 0ur work provides a mechanistic framework for the recognition of sequence-divergent peptide hormones in plants.Significance StatementTwo sequence-related plant membrane receptor kinases and their shape-complementary co-receptors are shown to selectively sense members of a small family of secreted peptide hormones to control formation of an important diffusion barrier in the plant root.

A two-way molecular dialogue between embryo and endosperm required for seed development

“…Consistent with the hypothesis that TPST acts in the same pathway as GSO1 and GSO2, no difference was observed between the phenotype of tpst-1 gso1-1 gso2-1 triple and gso1-1 gso2-1 10 double mutants (Fig. S2E).…”

“…We would like to thank Loïc Lepiniec for providing the tws1-1 and tws1-2 10 seeds and Carlos Galvan Ampudia for the pPIN1::GFP seeds. We would like to acknowledge…”

“…This pathway regulates the deposition of the embryonic cuticle which forms an essential hydrophobic barrier separating the apoplasts of the embryo and endosperm. After germination, the cuticle -one of the critical innovations underlying the transition of plants from 10 their original, aqueous environment to dry land -protects the seedling from catastrophic water loss (1,2).…”

“…1L). Mass spectroscopy analysis 10 of the TWS1 cleavage product purified from tobacco leaves showed that ALE1 cleaves TWS1 between His54 and Gly55 (Fig. S5).…”

“…Transformants could be obtained in tws1 mutants, but not in the wild-type background. Furthermore, when tws1 plants carrying the pTWS1:ALE1 transgene were pollinated with wild-type pollen to introduce a functional TWS1 allele into the zygotic compartments and thus induce colocalization of TWS1 precursors, ALE1 and the GSO receptors 10 in the embryo, premature embryo arrest was observed ( Fig. 3F-M) (Fig.…”