Identification of additional MAP kinases activated upon PAMP treatment

Mitogen-activated protein (MAP) kinase cascades play important roles in plant immunity. Upon pathogen associated molecular pattern (PAMP) treatment, MPK3, MPK6 and MPK4 are quickly activated by upstream MKKs through phosphorylation. Western blot analysis using α-phospho-p44/42-ERK antibody suggests that additional MPKs with similar size as MPK4 are also activated upon PAMP perception. To identify these MAP kinases, 7 candidate MPKs with similar sizes as MPK4 were selected for further analysis. Transgenic plants expressing these MPKs with a ZZ-3xFLAG double tag of 17 kD were generated and analyzed by western blot. MPK1, MPK11 and MPK13 were found to be phosphorylated upon treatment with flg22. Our study revealed additional MAPKs being activated during PAMP-triggered immunity.