Can the depletion of most of the assets of a plan (participant with more than half of the assets of the plan taking an in-service withdrawal) cause a partial plan termination?

I have never heard of a depletion in assets causing a partial plan termination. My understanding is that involuntary termination of 20% or more of the plan participants can cause a partial plan termination--I have also heard that plan amendments that significantly reduce future benefit accruals can also be grounds for a partial plan termination. You would have to make sure the asset withdrawal corresponds to the restricted benefit rules in the 401(a)(4) regs.

Amount of assets is not an issue with regard to plan termination.