Receptor-like kinase involved in the control of pollen germination and pollen tube polar growth (PubMed:23024212). The extracellular domain serves as a sensor for peptides derived from GRI (PubMed:25398910). May act as a downstream element for ROS-dependent cell death induced by GRI (PubMed:25398910). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with the GRI peptide. Expressed in pollen and/or in flowers (PubMed:12139002). Detected at low levels in leaves (PubMed:25398910). Up-regulated by biotic and abiotic stresses. The protein kinase domain may be catalytically impaired due to the lack of the conserved Asp active site at position 500, which is replaced by a His residue. No effect on pollen germination and growth. Prk2 and prk5 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.