Towards a non-chiral extension of SM and MSSM

We show that in some SU(N) type GUTs with complementary pairs of conjugated fermion multiplets the relatively light (M ⪡ MGUT) vectorlike fermions which considerably modify the desert physics naturally appear. In the non-SUSY case they can provide for the unification of the standard coupling constant α1, α2 and αs whereas in the SUSY case they can increase the unification point up to the string unification limit and decrease αs(Mz) to the value predicted by low energy physics.