  A simple unitarized quark-meson model, recently applied with success to light
and charmed scalar mesons, is shown to encompass Adler-type zeros in the
amplitude, due to the use of relativistic kinematics in the scattering sector.
These zeros turn out to be crucial for the description of the $K_0^*$(800)
resonance, as well as the new charmed scalar mesons $D_{s0}^*$(2317) and
$D_0^*$(2300). ~
