Fig. 1.

Schematic representation of AGC kinase signaling cascades in plant immune responses. a The tomato AGC kinase Adi3 is regulated by the PDK1 and Pto kinases to negatively modulate disease resistance and programmed cell death (PCD). Two parallel kinase pathways mediated by MAPKKKα and Pti1 kinases are activated downstream of Pto and also participate in the modulation of resistance and PCD. b The Arabidopsis AGC kinase OXI1 is activated by PDK1 and H₂O₂ and is required for disease resistance. OXI1 modulates the stress-induced activation of the MAPKs MPK3 and MPK6, putatively through its downstream kinase Pti1-4. c In rice, a phosphorylation cascade including OsPDK1, the AGC kinase OsOXI1 and the downstream kinase OsPti1a was shown to positively regulate disease resistance and cell death in response to H₂O₂ and pathogen recognition. Filled arrows represent direct regulation. Dashed arrows represent processes comprising various or unknown steps. Double-headed arrows represent protein association. PA phosphatidic acid