Guanine-nucleotide exchange factor (GEF) that acts as an activator of Rop (Rho of plants) GTPases by promoting the exchange of GDP for GTP. Active as homodimer. Homodimer. The homodimer interacts with ARAC5/ROP4. Interacts with ARAC11/ROP1 and ARAC10/ROP11. Interacts with PRK6 (PubMed:26961657). Localizes to the apical region of the pollen tube plasma membrane. Expressed in pollen grains and pollen tubes. The PRONE (plant-specific Rop nucleotide exchanger) domain is responsible for the GEF activity.