Disulfide bond sculpts a peptide fold that mediates phytocytokine recognition

Jimenez Sandoval, P.; Johanndrees, O.; Snoeck, S.; Harshith, C. Y.; Omary, M.; Broyart, C.; Rhodes, J.; Bender, K. W.; Zipfel, C.; Santiago, J.

doi:10.1101/2025.10.24.684422

bioRxiv · 10.1101/2025.10.24.684422

Disulfide bond sculpts a peptide fold that mediates phytocytokine recognition

Jimenez Sandoval, P.·Johanndrees, O.·Snoeck, S.·Harshith, C. Y.·Omary, M.·Broyart, C.·Rhodes, J.·Bender, K. W.·Zipfel, C.·Santiago, J.

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Abstract

Precise ligand recognition by closely related leucine-rich repeat receptor kinases (LRR-RKs) is essential for plants to coordinate immunity, development, and environmental adaptation. Here, we show how HAESA-LIKE 3 (HSL3) specifically recognizes the folded, disulfide-stabilized CTNIP/SCREW phytocytokines in Arabidopsis. Quantitative binding assays define a minimal CTNIP4 region required for high-affinity HSL3 interaction and signaling activation. A 2.12 [A] crystal structure of the HSL3-CTNIP4 complex reveals a unique C-terminal receptor pocket that accommodates the peptides cyclic architecture through a combination of hydrophobic and polar contacts, a feature absent in the closely related HAE/HSL LRR-RKs. The cyclic CTNIP4 fold further establishes a largely hydrophobic interface that bridges HSL3 to the SERK co-receptor, forming a distinct activation surface. Together, these structural, biochemical and physiological insights uncover a previously unrecognised mechanism of peptide perception and receptor activation, highlighting how subtle architectural variations enable precise ligand selectivity among highly conserved plant receptor kinases.

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Jimenez Sandoval, P., Johanndrees, O., Snoeck, S., Harshith, C. Y., Omary, M., Broyart, C., Rhodes, J., Bender, K. W., Zipfel, C., Santiago, J.. 2025-10-24. Disulfide bond sculpts a peptide fold that mediates phytocytokine recognition. https://doi.org/10.1101/2025.10.24.684422

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