Intramolecular disulfide bonds can modulate overall peptide rigidityimprove structural stability, thereby serving as essential post-translational modifications for signaling small secreted peptides (SSPs). Despite the widespread distribution of signaling SSPs with a single intramolecular disulfide bond, such as oxytocin, urotensin Ⅱ, vasopressin,somatostatin in animals, few analogous SSPs have been characterized in plants (DalyWilson, 2021). To date, only delta-like phytocytokines (DEPs) (Wang et al., 2025) have been functionally characterized as such SSPs in plants. SMALL PHYTOCYTOKINES REGULATING DEFENSEWATER LOSS (SCREW) (Liu et al., 2022)/CTNIPs (Rhodes et al., 2022) are phytocytokines that activate immune responses (e.g., mitogen-activated protein kinase [MAPK] phosphorylation)regulate stomatal closure through PLANT SCREW UNRESPONSIVE RECEPTOR (NUT)/HAESA-LIKE 3 (HSL3), which belongs to the leucine-rich repeat receptor-like kinase (LRR-RLK) XI subfamily. SCREW peptides activate NUT by promoting its heterodimerization with BRASSINOSTEROID INSENSITIVE 1-ASSOCIATED KINASE 1 (BAK1) (Liu et al., 2022). However, whether the biological function of SCREW2 depends on conformational changes induced by its disulfide bondthe underlying mechanisms governing the assembly of NUT–SCREW–BAK1 complexes remain elusive.