The cellular language ofmyo‐inositol signaling

SummaryThe simple polyol,myo‐inositol, is used as a building block of a cellular language that plays various roles in signal transduction. This review describes the terminology used to denotemyo‐inositol‐containing molecules, with an emphasis on how phosphate and fatty acids are added to create second messengers used in signaling. Work in model systems has delineated the genes and enzymes required for synthesis and metabolism of manymyo‐inositol‐containing molecules, with genetic mutants and measurement of second messengers playing key roles in developing our understanding. There is increasing evidence that molecules such asmyo‐inositol(1,4,5)trisphosphate and phosphatidylinositol(4,5)bisphosphate are synthesized in response to various signals plants encounter. In particular, the controversial role ofmyo‐inositol(1,4,5)trisphosphate is addressed, accompanied by a discussion of the multiple enzymes that act to regulate this molecule. We are also beginning to understand new connections ofmyo‐inositol signaling in plants. These recent discoveries include the novel roles of inositol phosphates in binding to plant hormone receptors and that of phosphatidylinositol(3)phosphate binding to pathogen effectors.ContentsSummary823I.Introduction824II.Structural and terminology considerations: adding phosphates and fatty acids tomyo‐inositol creates a chemical and cellular language for signaling824III.Hydrolysis of membrane PtdInsPs results in second messenger production825IV.What signals are linked to inositol signaling?826V.The controversial roles of DAG and Ins(1,4,5)P3in the plant cell826VI.A Multiplicity of enzymes that synthesize and metabolize Ins(1,4,5)P3829VII.New connections of inositol signaling in plants831VIII.Concluding remarks834Acknowledgements834References834