May be involved in intracellular signaling through interaction with PtdInsPs and calmodulin (CaM); may keep PtdInsPs attached to the plasma membrane until Ca(2+)-CaM reaches a competitive concentration subsequent to an increase triggered by a stimulus, thus leading to PtdInsPs release and subsequent activation of InsPs-dependent signaling cascade. Interacts competitively at the N-terminus with calcium ions and CaM (in a calcium-dependent manner), and with the phosphatidylinositol phosphates PtdIns(3,4,5)P(3), PtdIns(3,4)P(2), PtdIns(4,5)P(2) and PtdIns(3,5)P(2). Binds also weakly to PtdIns(3)P, PtdIns(4)P and PtdIns(5)P. Negative regulator of hypocotyl cell elongation by destabilizing cortical microtubules in a calcium-dependent manner. Binds directly to and destabilized microtubules to enhance microtubule depolymerization when cytoplasmic calcium increases. In case of Turnip mosaic virus (TuMV) infection, confers sensitivity by promoting viral cell-to-cell movement through interaction with viral P3N-PIPO. Binds 6 Cu(2+) ions per subunit. Decreased of the heat stability in the presence of metal ions (e.g. K(+), Ca(2+), Cu(2+), Sr(2+) and Mg(2+)). Results were obtained when excited at 277 nm. In the presence of copper ions, the maximum absorption peak disappears. Interacts with Turnip mosaic virus (TuMV) P3N-PIPO. Shuttles from plasma membrane to cytoplasm (e.g. colocalizes with cortical microtubules) upon calcium levels increase. Co-localizes with Turnip mosaic virus (TuMV) P3N-PIPO at the plasmodesmata. Additional isoforms seem to exist. Mostly expressed in the basal region of hypocotyls. Expressed in seedlings, roots, shoots, stems, leaves (e.g. in epidermis and vascular tissues), flowers (e.g. in pistils and anthers) and siliques (at protein level). Accumulates in response to CuCl(2), mannitol, sorbitol, and flagellin oligopeptide (e.g. flg22) treatments. Induced after long treatment (2 days) with NaCl, KCl, MgCl(2) and FeCl(3). Slight induction in Mg(2+) deprivation. Slightly repressed by dehydration. Long etiolated hypocotyls. Reduced accumulation and cell-to-cell movement of Turnip mosaic virus (TuMV) leading to an enhanced plant resistance. Belongs to the DREPP family.