高温下植物气孔散热新机制：UBP24分子电荷开关

比利时根特大学VIB植物系统生物学中心Ive De Smet团队在《Nature Plants》发表研究，揭示了植物在高温下打开气孔进行蒸腾散热的新机制。

研究发现，高温首先激活B4类RAF激酶，进而激活OST1蛋白激酶，使去泛素化酶UBP24的Ser360位点磷酸化，如同给UBP24“充电”，增强其在高温下的稳定性；随后UBP24去除质膜质子泵AHA1上的泛素修饰，阻止其内吞降解，维持质子泵活性与气孔开放。值得注意的是，这条通路不依赖脱落酸（ABA），表明OST1并非只负责ABA介导的关孔，而能随环境信号切换功能，这一“负电荷开关”在植物进化中亦被保留。

该研究将单个氨基酸位点的电荷状态与蛋白进化、信号转导和器官运动联系起来，为作物耐热育种提供了UBP24稳定性、AHA1周转等新靶点。
Protein evolution is shaped by sequence variation that modulates protein properties—for example, through the 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, which is activated by B4 RAF kinases in response to heat stress. This phosphorylation stabilizes UBP24, enabling the deubiquitylation of a plasma membrane H+-ATPase to promote stomatal opening. This reveals a 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 homologue 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 in plants and yeast and highlighting how charge-based regulation promotes cellular resilience under stress.