A model of CPL3-mediated DGK5 AS in regulating PA homeostasis and plant immunity. MAMP perception by the PRR complex triggers BIK1 phosphorylation and activation of two MAPK cascades. BIK1 phosphorylates DGK5 at Ser 506 and enhances its activity for PA production. In contrast, PRR-activated MPK4 phosphorylates DGK5 at Thr 446, leading to reduced DGK5 activity and PA production. In addition, MAMP perception induces RNAPII CTD phosphorylation through MPK3/6-activated CDKCs, counteracted by the CTD phosphatase CPL3. The CDKC-CPL3-mediated CTD phosphorylation regulates DGK5 AS, producing two isoforms, DGK5β and DGK5α. DGK5β, which can be phosphorylated by BIK1, positively regulates DGK5 activity and plant immunity. In contrast, DGK5α, unable to be phosphorylated by BIK1, is nonfunctional and likely negatively regulates PA production through MPK4-mediated Thr 446 phosphorylation to maintain PA homeostasis. Further, PA binds and stabilizes RBOHD in mediating ROS production in plant PRR-mediated PTI and NLR-mediated ETI. The figure was created with BioRender
