GmSAL1 Hydrolyzes Inositol-1,4,5-Trisphosphate and Regulates Stomatal Closure in Detached Leaves and Ion Compartmentalization in Plant Cells

<div><p>Inositol polyphosphatases are important regulators since they control the catabolism of phosphoinositol derivatives, which are often signaling molecules for cellular processes. Here we report on the characterization of one of their members in soybean, GmSAL1. In contrast to the substrate specificity of its <i>Arabidopsis</i> homologues (AtSAL1 and AtSAL2), GmSAL1 only hydrolyzes inositol-1,4,5-trisphosphate (IP₃) but not inositol-1,3,4-trisphosphate or inositol-1,4-bisphosphate.The ectopic expression of <i>GmSAL1</i> in transgenic <i>Arabidopsis thaliana</i> led to a reduction in IP₃ signals, which was inferred from the reduction in the cytoplasmic signals of the <i>in vivo</i> biomarker pleckstrin homology domain–green florescent protein fusion protein and the suppression of abscisic acid-induced stomatal closure. At the cellular level, the ectopic expression of <i>GmSAL1</i> in transgenic BY-2 cells enhanced vacuolar Na⁺ compartmentalization and therefore could partially alleviate salinity stress.</p> </div