Multi-layered defense barriers ensure that a plant is the host to only a few adapted pathogens. Thus, the host range of a particular pathogen relies on its ability to avoid being recognized by plant. One of the common strategies to subvert host defense is the production of a defense suppressor. In the case of Mycosphaerella pinodes , a causal agent of Mycosphaerella blight on pea, this fungus can suppress or delay host defense by secreting suppressors named supprescins A and B. In parallel, we discovered a constituent(s) similar to the fungal supprescins from healthy leaves of pea, which we named endogenous suppressor (ES). Recently, we successfully isolated Arabidopsis ES from healthy leaves and identified one as c-terminally encoded peptides (CEP). Indeed, exogenous CEP as a synthetic peptide enhanced disease susceptibility to both non-adapted fungal and bacterial pathogens. Here a potential role of CEP peptides in plant-microbe interaction and their physiological relevance will be discussed. • An endogenous suppressor (ES) is defined as constitute(s) synthesized by plant, which suppress (es) elicitor-induced defense responses. • Recently, we successfully isolated Arabidopsis ES from healthy leaves and identified one as c-terminally encoded peptides (CEP). Indeed, exogenous CEP as a synthetic peptide enhanced disease susceptibility to both non-adapted fungal and bacterial pathogens. • So far, studies on the activation of plant immunity have been extensively carried out, but little is known about endogenous molecule(s) that negatively modulate plant immunity. • Here a potential role of CEP peptides in plant-microbe interaction and their physiological relevance will be discussed. [ABSTRACT FROM AUTHOR]