The present invention relates to plant transcriptional activators and mutants thereof. Furthermore, the present invention relates to uses of plant transcriptional activators and mutants thereof for increasing plant defence responses to pathogens. In particular, the present invention relates to a peptide which confers increased pathogen resistance upon a plant expressing said peptide, said peptide having a sequence selected from the group consisting of SEQ ID NO:1, SEQ ID NO:2, SEQ ID NO:3, and SEQ ID NO:4 mutated at a position selected from the group consisting of Glu271, Trp272 and residues between and including Pro123 to Gly128, an ortholog thereof, a homolog thereof, a functionally active fragment thereof or a functionally active variant thereof.