摘要Mitogen-activated protein kinase(MAPK)cas-cades play pivotal roles in plant defense against phytopathogens downstream of im-mune receptor complexes.The amplitude and duration of MAPK activation must be strictly controlled,but the underlying mechanism re-mains unclear.Here,we identified Arabidopsis CPL1(C-terminal domain phosphatase-like 1)as a negative regulator of microbe-associated molecular pattern(MAMP)-triggered immunity via a forward-genetic screen.Disruption of CPL1 significantly enhanced plant resistance to Pseudomonas pathogens induced by the bac-terial peptide flg22.Furthermore,flg22-induced MPK3/MPK4/MPK6 phosphorylation was dra-matically elevated in cpl1 mutants but severely impaired in CPL1 overexpression lines,sug-gesting that CPL1 might interfere with flg22-induced MAPK activation.Indeed,CPL1 di-rectly interacted with MPK3 and MPK6,as well as the upstream MKK4 and MKK5.A firefly luciferase-based complementation assay in-dicated that the interaction between MKK4/MKK5 and MPK3/MPK6 was significantly re-duced in the presence of CPL1.These results suggest that CPL1 plays a novel regulatory role in suppressing MAMP-induced MAPK cascade activation and MAMP-triggered immunity to bacterial pathogens.