In plants and animals, innate immunity is triggered through pattern recognition receptors (PRRs) in response to microbe-associated molecular patterns (MAMPs) to provide the first line of inducible defense. Plant receptor protein kinases (RPKs) represent the main plasma membrane PRRs perceiving diverse MAMPs. RPKs also recognize secondary danger-inducible plant peptides and cell-wall signals. Both types of RPKs trigger rapid and convergent downstream signaling networks controlled by calcium-activated PKs and mitogen-activated PK (MAPK) cascades. These PK signaling networks serve specific and overlapping roles in controlling the activities and synthesis of a plethora of transcription factors (TFs), enzymes, hormones, peptides and antimicrobial chemicals, contributing to resistance against bacteria, oomycetes and fungi.