Work

Evolutionary tuning of the molecular charge state of UBP24 shapes responses to high temperature

Year: 2026

Type: article

Abstract: Protein evolution is shaped by sequence variation that modulates protein properties, e.g., through gain or loss of post-translational modifications. Among these, reversible phosphorylation alters a protein’s overall electrical charge and enables organisms to dynamically respond to environmental fluctuations. In plants, the hydro-active opening of stomata, microscopic pores that regulate gas exchange and leaf temperature, is governed by phosphorylation-dependent signalling. Here, we identify a mechanism involving the deubiquitylase UBIQUITIN-SPECIFIC PROTEASE 24 (UBP24) that promotes stomatal opening in Arabidopsis thaliana under heat. UBP24 is phosphorylated at serine 360 by the kinase OPEN STOMATA 1 (OST1), which is activated by B4 RAF kinases in response to heat stress. This phosphorylation stabilizes UBP24, enabling deubiquitylation of a plasma membrane H⁺-ATPase to promote stomatal opening. This reveals a novel heat-responsive signalling pathway that evolved in vascular plants to regulate stomatal function. Strikingly, a similar evolutionary feature exists in Saccharomyces cerevisiae, where the UBP24 homolog Ubp3 requires a constitutively negatively charged residue at the homologous site to support growth after heat shock. Our findings uncover a conserved molecular mechanism in which negative charge, via phosphorylation or acidic residues, modulates deubiquitylase function, supporting adaptive thermal responses across eukaryotes and highlighting how charge-based regulation promotes cellular resilience under stress.

Source: Nature Plants

DOI: 10.1038/s41477-026-02345-1