Reduce the 1M slightly, to say 47k to make it a weak pulldown. This keeps the gate from drifting and makes the FET shut off in case of - ahem - firmware bugs that accidentally misconfigure it. It will also keep it low during power-on reset until the pin is - ahem - correctly configured. And, finally, on power-off as rails ramp down and the µC is suspended by the brownout detection circuitry, it shuts off the FET should the firmware - ahem - "forget to".