Plays a continuous role in plant development probably in the structural organization of compartments (By similarity). Seems to be involved in early gravitropic signal transduction within the gravity-perceiving cells (statocytes), where it influences pH changes and auxin distribution. Probably affects the localization and/or activity of auxin efflux carrier components (PIN proteins) or other proteins involved in lateral auxin transport. Found in endoplasmic reticulum, Golgi, vesicles near the plasma membrane and around cell plate, and bound to the plasma membrane. Probably interacts with integral membrane proteins. Also interacts with cytoskeleton. Expressed at high levels in root cap, root tip meristematic region and elongation zones, and at lower levels in mature part of roots (at protein level). Constitutively expressed in seedlings, etiolated or not, roots, rosette leaves, cauline leaves, stems, flowers, siliques and pollen. Roots and hypocotyls reorient slowly upon gravistimulation. Plants are normal for phototropism and for responses to hormones such as auxin, abscisic acid, gibberellins and ethylene. They also accumulate starch like the wild-type. In response to gravistimulation arg1-2 lacks cytoplasmic pH changes in columella cells and has a bad repartition of auxin that accumulates in root tips instead of forming a gradient. Belongs to the DnaJ family. B/II subfamily.