Receptor-like kinase involved in the control of pollen germination and pollen tube polar growth (PubMed:23024212). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts in vitro with ROPGEF1 (via PRONE domain). Preferentially localized to the apical region of the pollen tube plasma membrane. Expressed in pollen and/or in flowers, but not in leaves. The protein kinase domain may be catalytically impaired due to the lack of the conserved Asp active site at position 485, which is replaced by a His residue. No effect on pollen germination and growth. Prk1 and prk2 double mutant has no effect on pollen germination and growth. Prk1, prk2 and prk5 triple mutant shows reduced pollen tube elongation. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.