Receptor protein kinase (PubMed:22899082). Could play a role in a differentiation signal (By similarity). Controls formative cell division in meristems (By similarity). Regulates epidermal cell differentiation in many organs (PubMed:22332708, PubMed:22899082). During floral organogenesis, required to maintain the interlocking of the palea and lemma, and fertility (PubMed:22332708). Triggers culm elongation (PubMed:22899082). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Homodimer. Also localized into protein export bodies. Specifically expressed in the epidermal cells of paleas and lemmas. Highly expressed in young vegetative and reproductive tissues, including calli, roots, seedlings, internodes, leaf blades and coleoptiles as well as young panicles and kernels. But low levels in 3-week-old sheaths and reproductive organs. During early spikelet development, accumulates in inflorescences, especially in the outermost cell layers. Present strongly in the palea and lemma epidermal cell layers, mostly at the position of the interlock. Also observed in reproductive organs, such as stigmas, stamens, lodicules, young kernels and seed coats. Regulated by GRF10 and GRF6 at the transcription level in floral organs during floret development. Autophosphorylated. Abnormal epidermis cells walls with discontinuous cuticles, leading to irregular architecture and organ self-fusion resulting in distorted interlocking structures of the palea and lemma which accumulates abnormal levels of anthocyanin after heading. Delayed separation of the palea and lemma at later spikelet stages. Severe interruption of pistil pollination and damage to the development of embryo and endosperm, with defects in aleurone and reduced seed fertility (PubMed:22332708). Reduced stature due to shorter primary and lateral tillers (PubMed:22899082). Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.