Characterization of <em>Arabidopsis</em> Myotubularins AtMTM1and AtMTM2: from Development to Stress Adaptation

Abstract

Myotubularins belong to a unique subgroup of a large family of dual-specificity serine–threonine phosphatase (DSP) that dephosphorylates serine / threonine as well as tyrosine residues. In <em>Arabidopsis thaliana</em> they are represented by two copies (AtMTM1 and AtMTM2) which cleave the D3 phosphate from phosphatidylinositol 3-phosphate (PtdIns3P) and phosphatidylinositol 3,5-bisphosphate [PtdIns(3,5)P₂], generating phosphatidylinositol (PtdIns) and phosphatidylinositol 5-phosphate (PtdIns5P), respectively. They are made of similar structural domains and have conserved biochemically active catalytic sites. Despite of sharing lots of similarities, these proteins behave in different manner. In this study, different subcellular localization of these plant myotubularins is reported. Here we report that AtMTM1 is playing an important role in ABA-induced stomata movements via its product PtdIns5P. Our results show that PtdIns5P is relevant for ABA-induced ROS generation, acting as an oxidative stress-induced second messenger, controlling the stomata behavior. Three isoforms of AtMTM1 were studied in order to understand the role of different domains of AtMTM1. The study of plant myotubularins represents a promising approach for improving crop performance under stress conditions.