Plant hormones are a structurally diverse collection of small molecules that control plant growth, development, and environmental responses. Work over the past two decades has established that many plant hormones directly stabilize protein-protein complexes and act analogously to chemical dimerization agents, which were first described for the immunosuppressants rapamycin, FK506, and cyclosporin. For example, abscisic acid (ABA), which regulates plant transpiration, stabilizes a complex between soluble ABA receptors and downstream phosphatases; the ABA-induced complex inhibits phosphatase activity, which in turn derepresses downstream kinases and activates signaling. I will describe my lab’s work on this sensing module and our efforts to design both synthetic ABA receptor agonists and engineer receptors with altered ligand binding properties. An unusually large family of receptors encodes ABA receptors and, until recently, it was unclear if selective or pan-agonists would be required to effectively control plant water use and drought tolerance; to address thus we have developed multiple selective receptor agonists and used these in combination genetic analyses to define Pyrabactin Resistance 1 (PYR1) and its close relatives as key targets that can be leveraged to control transpiration. I will also describe a new fully orthogonal signaling module that is insulated from endogenous signaling components and controlled by a non-native agrochemical. This engineered dimerization module provides a simple platform technology for programming crops with agrochemically controlled traits.