Receptor with a serine/threonine-protein kinase activity (By similarity). Together with SKM1, LRR-rich receptor-like kinase (LRR-RLK) required for male fertility by the perception of CLE43 and CLE45 peptides and the transduction of their promoting action in pollen tubes, especially under relatively high temperature (at 30 degrees Celsius), thus conferring tolerance against high temperature probably through the maintenance of mitochondrial activity (PubMed:23910659). Seems to not be involved in the perception of CLE45 peptide in roots (PubMed:27354416). Together with RGI1, RGI2, RGI3, RGI4 and RGI5, acts as receptor of RGF1, a peptide hormone that maintains the postembryonic root stem cell niche by regulating the expression levels and patterns of the transcription factor PLETHORA (PLT) (PubMed:27229312, PubMed:27229311). Links RGF1 signal with its downstream components (PubMed:27229311). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Self-interacts (By similarity). Interacts with RGF1; this interaction triggers its phosphorylation and ubiquitination and the formation of heterodimers with SERK1 (PubMed:27229311). Expressed in floers, pollen grains and stipules (PubMed:23910659, PubMed:27229311). Present in roots (PubMed:27354416, PubMed:27229311). Present throughout the root, starting from the transition zone and including transition and elongation zones, but absent from the meristem. Slightly induced in pollen upon high-temperature exposure (HTE). Autophosphorylated. Phosphorylated and ubiquitinated upon interaction with RGF1, thus leading to activation a subsequent degradation. Smaller root meristem size and fewer root meristematic cortex cells, associated with shorter roots and a slighty reduced sensitivity to RGF1 (PubMed:27229311). Insensitivity of pollen tubes to CLE43 and, partially, to CLE45 peptides-mediated growth stimulation (PubMed:23910659). Pollen tubes of plants missing both SKM1 and SKM2 are fully insensitive to CLE45 peptides (PubMed:23910659). Quintuple mutants rgi1 rgi2 rgi3 rgi4 rgi5 display a consistent short primary root phenotype with a small size of meristem associated with a total insensitivity to RGF1 and undetectable levels of PLT1 and PLT2 (PubMed:27229312). Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.