Plant Chemical Genomics

Masanori Okamoto, Sean R. Cutler, Okamoto, Masanori, Cutler, Sean R.

This chapter describes procedures to find small molecules that bind to abscisic acid (ABA) receptors and improve plant tolerance to water stress. Abscisic acid promotes the interaction between ABA receptors and protein phosphatase 2Cs (PP2Cs), which are negative regulators of ABA signaling. This receptor-mediated ABA-dependent inhibition of PP2C activity is required for ABA action in vivo. ABA agonists can be identified by high-throughput screening for molecules that promote agonist-induced ABA receptor-PP2C interactions using yeast two-hybrid assays. In addition to in vitro assays, an in vivo test to evaluate ABA agonist activity has been devised in which an ABA-inducible GUS reporter strain is used to evaluate the effect of each ABA agonist. The effects of ABA agonists can also be determined using thermal imaging analyses and a water loss assay of stomata. Finally, the ability of each ABA agonist to confer drought stress tolerance upon plants grown in soil is determined. These methods can be used to identify various ABA agonists that protect plants against water stress.