AtPep-induced PDF1.2 and PR-1 expression is blocked in mutant plants. (A) Relative expression of PDF1.2 in leaves of wild-type Arabidopsis, fad triple-mutant, and ein2-1 plants leaves supplied with 20 nM solution of AtPep peptides through their cut petioles, compared with control leaves supplied with water. (B) Expression of PR-1 in leaves from wild-type Arabidopsis, sid2-2, and npr1-1 mutant plants supplied with 20 nM AtPep peptides through their cut petioles relative to leaves supplied with water. Expression of PDF1.2 and PR-1 was determined by semiquantitative RT-PCR.