Measurement of Inositol (1,4,5) Trisphosphate in Plant Tissues by a Competitive Receptor Binding Assay

The phosphoinositide signaling pathway is important for plant responses to many different stresses. As part of the responses to a stimulus, InsP₃ levels may increase rapidly and transiently. The receptor binding assay for InsP₃ described here is easy to use and an ideal method to monitor and compare InsP₃ levels in multiple samples from large scale experiments. The method is based on competitive binding of InsP₃ to the mammalian brain InsP₃ specific receptor protein. This chapter describes a protocol for extracting and neutralizing plant samples and performing the receptor binding assay (using a commercially available kit). The protocol described has been used effectively to monitor InsP₃ levels in plant tissues of different origin and in response to different stresses.