A protein called abscisic acid, or ABA, helps plants to acclimate to stressful changes in the environment. During a drought, plants produce ABA. Receptors then recognize ABA and induce a response, ultimately causing the plant to close pores in its leaves and stems so that less water evaporates and the plant is less likely to wilt.
Plants sense ABA using chemical-induced dimerization (CID) modules, composed of the receptor PYR1 and HAB1, a phosphatase inhibited by ligand-activated PYR1. The ligand recognition in this system can be reprogrammed. Ian Wheeldon, Sean R. Cutler, University of California, Riverside, USA, and colleagues have expanded the system to recognize certain compounds as activating ligands in order to create living sensors, e.g., to indicate the presence of toxic pesticides.
The team designed an ABA-regulated PYR1/HAB1 sensor that functions orthogonally to the wild type and used it to create systems that show nanomolar sensitivities towards the activating ligands mandipropamid and azinphos-ethyl. Mandipropamid is a fungicide.
Azinphos-ethyl is an organophosphate pesticide that is banned in many countries. Once the receptors, which were introduced into Arabidopsis thaliana plants, bind to this pesticide, the plants turn beet red. This is due to the expression of the beet pigment betalain driven by the sensor system.
The researchers also demonstrated the ability to turn another living organism into a biosensor: yeast (Saccharomyces cerevisiae). They were able to show a response in yeast to both mandipropamid and azinphos-ethyl at the same time via two separate reporter genes.
- An orthogonalized PYR1-based CID module with reprogrammable ligand-binding specificity,
Sang-Youl Park, Jingde Qiu, Shuang Wei, Francis C. Peterson, Jesús Beltrán, Angélica V. Medina-Cucurella, Aditya S. Vaidya, Zenan Xing, Brian F. Volkman, Dmitri A. Nusinow, Timothy A. Whitehead, Ian Wheeldon, Sean R. Cutler,
Nat. Chem. Biol. 2023.