Higher plants deploy a large repertoire of Pattern-Recognition Receptors (PRRs),composed of Receptor Kinases (RKs) or Receptor Proteins (RPs) to perceive in the apoplast molecular patterns of microbe or plant origin during infection,activating pattern-triggered immunity (PTI).Previous and ongoing studies in our and other labs show that a subfamily of cytoplasmic kinases including BIK1 and PBS1-Like (PBL) proteins play a central role in PTI by acting directly downstream of multiple PRRs.They regulate important downstream signaling events including production of ROS,calcium influx,and MAPK activation,and are subject to tight regulations by heterotrimeric G proteins and ubiquitination proteasome system.