OPEN STOMATA1 opens the door to ABA signaling in Arabidopsis guard cells

The plant hormone abscisic acid plays a crucial role in plant responses to drought, salinity and cold. A recent report shows that mutations in the OST1 gene, encoding a serine-threonine protein kinase, render Arabidopsis thaliana guard cells insensitive to abscisic acid, such that stomata remain open in the presence of this phytohormone.