A Luciferase Reporter Assay to Identify Chemical Activators of ABA Signaling.

Plant stress tolerance relies on intricate signaling networks that are not fully understood. Several plant hormones are involved in the adaptation to different environmental conditions. Abscisic acid (ABA) has an essential role in stress tolerance, especially in the adaptation to drought. During the last years, chemical genomics has gained attention as an alternative approach to decipher complex traits. Additionally, chemical-based strategies have been very useful to untangle genetic redundancy, which is hard to address by other approaches such as classical genetics. Here, we describe the use of an ABA-inducible luciferase (LUC) reporter line for the high-throughput identification of chemical activators of the ABA signaling pathway. In this assay, seven-day-old pMAPKKK18-LUC ⁺ seedlings are grown on 96-well plates and treated with test compounds. Next, the activity of the LUC reporter is quantified semiautomatically by image analysis. Candidate compounds able to activate the reporter are thus identified and subjected to a secondary screen by analyzing their effect on ABA-related phenotypes (e.g., inhibition of seed germination). This assay is fast, high-throughput, nondestructive, semiquantitative and can be applied to any other luciferase reporter lines, making it ideal for forward chemical genetic screenings.