3.2. Structure-dependent activity of iturin A in the induction of
plant defense response
To determine whether plant defense response induction by
iturin A is structure-dependent, we synthesized three iturin A de-
rivative peptides (Fig. 3A). Iturin A inhibited the mycelial growth of
fungal plant pathogen C. gloeosporioides, whereas all the derivative
peptides lost their antagonistic effect on the fungus (Fig. 3B).
As described above, iturin A induced PR1 and PDF1.2 gene
expression in the untreated leaves of wild plants (Fig. 3C and D).
When wild plants were exposed to the three iturin A derivative
peptides, PR1 and PDF1.2 gene expression was not systemically
upregulated in the untreated leaves. The ATAGPA peptide, in
particular, drastically decreased the expression of both genes in the
untreated leaves compared with control plants (Fig. 3D).