4. Discussion
The predicted signaling pathways of LAR and SAR triggered by
iturin A are shown in Fig. 4. Plant cells recognize iturin Athrough an
unknown mechanism, probably through receptor recognition and/
or bilayer perturbation of plasma membranes. The recognition
guides the cells to early events triggering plant defense response.
When the SA signaling pathway is activated, NPR1 is transported to
the nucleus in response to SA [8], where it upregulates defense
gene expression, such as PR1. The JA signaling pathway is positively
regulated by the recognition, and MYC2 induces defense gene
expression, such as PDF1.2 [10]. Consequently, LAR is induced in
local tissues exposed to iturin A. SA and JA signals are transported
in the phloem and then to systemic tissues from the phloem.
Similar to local tissues, in iturin A untreated cells, SA and JA induce
defense gene expression through NPR1-and MYC2-related signal
transduction, respectively. Finally, SAR is systemically expressed in
distant tissues.