Phosphatase with phosphoinositide 3'-phosphatase activity that can use phosphatidylinositol-3-phosphate (PtdIns3P) and phosphatidylinositol-3,5-diphosphate (PtdIns3,5P(2)) as substrates and produces phosphatidylinositol-5-phosphate (PtdIns5P); participates in pathway(s) that transfer gene regulatory signals to the nucleus. Required for recovery after water deprivation, via the accumulation of PtdIns5P upon dehydration; high PtdIns5P levels mediate ATX1 cytoplasmic localization, thus down-regulating the expression of ATX1-dependent genes. Confers sensitivity to soil-water-deficit stress. a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol-3-phosphate) + H2O = a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol) + phosphate a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol-3,5-bisphosphate) + H2O = a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol-5-phosphate) + phosphate Present in granular particles of varying abundance and size at the cell periphery and throughout the cytoplasm. Mostly expressed in siliques and leaves (including hydathodes), and, to a lower extent, in flowers and roots. Expressed in young seedlings, especially at the tip of the growing shoot meristems. Later observed in roots and in aerial parts. Weakly expressed in leaves with local higher levels in the trichomes, hydathodes and in cotyledon veins. Present at low levels in flowers with higher accumulation in cells at organ-stem junctions, as well as in the septum and the funiculi of the developing siliques. Also observed in a diffuse pattern, appearing as patches along the stem but also concentrated at the peduncle. Accumulates upon dehydration. No visible phenotype in normal conditions. Impaired accumulation of PtdIns5P in response to stress such as dehydration, leading to an increased resistance. Belongs to the protein-tyrosine phosphatase family. Non-receptor class myotubularin subfamily.