Rho GTPase-activating protein involved in the signal transduction pathway (By similarity). Regulator of the contractile vacuole network as well as involved in driving vacuole emptying. Show a subtle phototaxis defect. mgp1-/mgp2-cells have a severe fruiting defect, an overabundance of filopodia and slug motility and function are affected. They empty their contractile vacuoles less efficiently than normal and consequently they have three times the usual number.