Homogeneous special manifolds, orientifolds and solvable coordinates

We discuss some geometrical properties of the underlying N=2 geometry which encompasses some low-energy aspects of N=1 orientifolds as well as four-dimensional N=2 Lagrangians including bulk and open string moduli. In the former case we illustrate how properly defined involutions allow to define N=1 Kaehler subspaces of special quaternionic manifolds. In the latter case we show that the full shift symmetry of the brane coordinates, which is Abelian in the rigid limit, is partially distorted by bulk fields to a nilpotent algebra