Phytosulfokine receptor with both a serine/threonine-protein kinase activity and a guanylate cyclase activity (PubMed:21504901). Regulates, in response to phytosulfokine binding, a signaling cascade involved in plant cell differentiation, organogenesis, somatic embryogenesis, cellular proliferation and plant growth. Involved in plant immunity, with antagonistic effects on bacterial and fungal resistances (PubMed:23062058). Not involved in PSY perception. CNGC17 and AHAs form a functional cation-translocating unit that is activated by PSKR1/BAK1 and possibly other BAK1/RLK complexes (PubMed:26071421). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] GTP = 3',5'-cyclic GMP + diphosphate cGMP suppresses kinase activity. Homo- and heterodimers with PSY1R (PubMed:25267325). Heterodimers with the somatic embryogenesis receptor-like kinases (SERKs) (PubMed:26308901). PSK is not directly involved in PSKR-SERK interaction but stabilizes PSKR island domain for recruitment of a SERK (PubMed:26308901). Part of a functional complex containing PSKR1, BAK1, CNGC17, and AHA (PubMed:26071421). Interacts with AHA1, AHA2, and BAK1, but not with CNGC17 or BRI1 (PubMed:26071421). Weakly expressed in roots, leaves, stems and flowers (PubMed:16829587). Expressed in the primary and lateral roots, including root primordia and root tips, but not in the hypocotyl (PubMed:19076296). Up-regulated by fungal infection and wounding. Gradual loss of individual cells potential to form callus as the tissues mature (PubMed:16829587). Premature senescence of the leaves (PubMed:17989228). Limitted root growth (PubMed:19076296). Enhanced resistance to bacterial biotrophic pathogens, but increased susceptibility to necrotrophic fungal infection (PubMed:23062058). PSKR1 and PSYR1 mediate a signaling pathway by two distinct ligands, which redundantly contribute to cellular proliferation and plant growth. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.