Phytocytokine signalling reopens stomata in plant immunity and water loss

Stomata exert considerable effects on global carbon and water cycles by mediating gas exchange and water vapour(1,2). Stomatal closure prevents water loss in response to dehydration and limits pathogen entry(3,4). However, prolonged stomatal closure reduces photosynthesis and transpiration and creates aqueous apoplasts that promote colonization by pathogens. How plants dynamically regulate stomatal reopening in a changing climate is unclear. Here we show that the secreted peptides SMALL PHYTOCYTOKINES REGULATING DEFENSE AND WATER LOSS (SCREWs) and the cognate receptor kinase PLANT SCREW UNRESPONSIVE RECEPTOR (NUT) counter-regulate phytohormone abscisic acid (ABA)- and microbe-associated molecular pattern (MAMP)-induced stomatal closure. SCREWs sensed by NUT function as immunomodulatory phytocytokines and recruit SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE (SERK) co-receptors to relay immune signalling. SCREWs trigger the NUT-dependent phosphorylation of ABA INSENSITIVE 1 (ABI1) and ABI2, which leads to an increase in the activity of ABI phosphatases towards OPEN STOMATA 1 (OST1)-a key kinase that mediates ABA- and MAMP-induced stomatal closure(5,6)-and a reduction in the activity of S-type anion channels. After induction by dehydration and pathogen infection, SCREW-NUT signalling promotes apoplastic water loss and disrupts microorganism-rich aqueous habitats to limit pathogen colonization. The SCREW-NUT system is widely distributed across land plants, which suggests that it has an important role in preventing uncontrolled stomatal closure caused by abiotic and biotic stresses to optimize plant fitness.

Automated summary

Stomatal reopening in plants is dynamically regulated by the interaction between secreted peptides SCREWs and the receptor kinase NUT. This system counter-regulates the closure of stomata induced by abscisic acid and microbe-associated molecular patterns. SCREWs trigger the phosphorylation of key proteins involved in stomatal closure, leading to increased activity of kinase OST1 and reduced activity of anion channels. The SCREW-NUT system plays an important role in preventing uncontrolled stomatal closure and optimizing plant fitness.