Wess-Zumino term in the SYM effective action revisited

The low-energy effective action for the super Yang-Mills on the Coulomb branch is known to include an SO(6)-invariant Wess-Zumino (WZ) term for the six scalar fields. For each maximal, non-anomalous subgroup of the SU(4) R-symmetry, we find a four-dimensional form of the WZ term with this subgroup being manifest. We then show that a recently proposed expression for the four-derivative part of the effective action in USp(4) harmonic superspace yields the WZ term with manifest SO(5) R-symmetry subgroup. The SU(2) harmonic superspace form of the effective action produces the WZ term with manifest SO(4) × SO(2). We argue that there is no four-dimensional form of the WZ term with manifest SU(3) R-symmetry, which is relevant for and superspace formulations of the effective action.