The plant aquaporin plasma membrane intrinsic proteins (PIP) subfamily
represents one of the main gateways for water exchange at
the plasma membrane (PM). A fraction of this subfamily, known as
PIP1, does not reach the PM unless they are coexpressed with a PIP2
aquaporin. Although ubiquitous and abundantly expressed, the role
and properties of PIP1 aquaporins have therefore remained masked.
Here, we unravel how FaPIP1;1, a fruit-specific PIP1 aquaporin from
Fragaria x ananassa, contributes to the modulation of membrane
water permeability (Pf) and pH aquaporin regulation. Our approach
was to combine an experimental and mathematical model
design to test its activity without affecting its trafficking dynamics.
We demonstrate that FaPIP1;1 has a high water channel activity
when coexpressed as well as how PIP1–PIP2 affects gating
sensitivity in terms of cytosolic acidification. PIP1–PIP2 random heterotetramerization
not only allows FaPIP1;1 to arrive at the PM but
also produces an enhancement of FaPIP2;1 activity. In this context,
we propose that FaPIP1;1 is a key participant in the regulation
of water movement across the membranes of cells expressing
both aquaporins.