  The PQ mechanism resolving the strong CP problem and the seesaw mechanism
explaining the smallness of neutrino masses may be related in a way that the PQ
symmetry breaking scale and the seesaw scale arise from a common origin.
Depending on how the PQ symmetry and the seesaw mechanism are realized, one has
different predictions on the color and electromagnetic anomalies which could be
tested in the future axion dark matter search experiments. Motivated by this,
we construct various PQ seesaw models which are minimally extended from the
(non-) supersymmetric Standard Model and thus set up different benchmark points
on the axion-photon-photon coupling in comparison with the standard KSVZ and
DFSZ models.
