Receptor-like protein kinases (RLKs) are single-pass transmembrane protein kinases critically involved in cell-to-cell and cell-to-environment communications.There are more than 400 typical RLKs in Arabidopsis.Based on their extracellular domain structures, RLKs were classified into 13 families.Among them, leucine-rich repeat (LRR) RLKs belong to the largest family, possessing at least 223 members.Somatic embryogenesis receptor kinases (SERKs) are a small group of LRR-RLKs, consisting of only 5 members.The first SERK was identified as a marker gene in carrot suspension cultures to monitor cell identity change from somatic to embryonic cells.Recent studies from several labs indicated that Arabidopsis SERKs play important roles in regulating distinct signaling pathways such as brassinosteroid (BR) signaling, cell death control, and various innate immune responses.Gene expression profile analyses and gain-of-function genetic data suggest that at least one of the Arabidopsis SERKs, SERK1, is likely involved in mediating embryo development.