I get how Turbo's work, I get how waste gates and blow off valves work and why...but I'm having trouble with one question:

In an automatic car, what happens in regards to boost pressure during a shift?

Here is what I have so far: The throttle plate stays open (so long as you have your foot planted) so there is no need for the waste gate to cycle open, but the engine looses speed and exhaust gas velocity and pressure so, naturally, the boost has to change...how is this managed in an automatic? Does the compressor just absorb the speed loss because its still out of range of stall? does it still vent back to the compressor? what happens in those 200‚ÄĒ700 ms?