  We study six-dimensional (6D) SU(6) supersymmetric models where the
doublet-triplet splitting, quark-lepton mass relations and gaugino-mediated
supersymmetry breaking are taken into account. We find that effective 4D gauge
coupling constants have highly nontrivial behavior between two compactification
scales. It is shown that realistic patterns of Yukawa coupling constants are
obtained for valid values of parameters and that hierarchical numbers are
generated via suppression by extra-dimensional effects.
