Binds to phosphatidic acid and to phosphoinositides such as PtdIns3P, PtdIns(3,4)P(2), PtdIns(3,4,5)P(3) and PtdIns(4,5)P(2). Catalyzes guanine nucleotide exchange on specific Rab proteins. Mostly expressed in flowers, and, to a lower extent, in stems, leaves, siliques, seeds.