Fungal elicitor Pep-25 increases cytosolic calcium ions, H2O2 production and activates the octadecanoid pathway in Arabidopsis thaliana

Transgenic Arabidopsis thaliana plants expressing the protein aequorin were used to investigate the transient change in cytosolic calcium ions caused by stimulation through the fungal elicitor Pep-25. Our results show that the elicitor Pep-25 derived from Phytophthora sojae can induce H2O2 production and an increase in cytosolic calcium ions. The transcription of LOX, OPR3, PED, AOS, AOC genes and the protein accumulation of AOS were induced by Pep-25 treatment. Pep-25 also induced an accumulation of jasmonic acid (JA). Blocking the production of H2O2 and the increase of cytosolic calcium ions both suppressed the transcription of LOX, OPR3, PED, AOS, AOC genes, the accumulation of AOS, and the accumulation of JA. These results indicated that the production of H2O2 derived from the plasma-membrane NADPH oxidase and the subsequently increase of cytosolic calcium ions are both required for the activation of the octadecanoid pathway by Pep-25 treatment in A. thaliana.