Early responses in methyl jasmonate-preconditioned cells toward pathogen-derived elicitors.

Early, signal transduction-related responses in cultured tobacco cells due to methyl jasmonate (MeJa), a cell-wall-derived elicitor from Phytophthora nicotianae and chitosan, were investigated. MeJa was an effective inducer of lipid peroxidation and lipoxygenase (LOX) activity with maximum levels reached within 2 h and 4-8 h, respectively. Chitosan and the elicitor induced a transient increase (1-4 h) in lipid peroxidation. Conditioning with MeJA, followed by secondary elicitation, led to a significant increase in malondialdehyde concentration after 1 h. Chitosan and the elicitor induced transient activation of LOX with maximal values between 8 and 12 h, with preconditioning resulting in a rapid increase in LOX activity at 4 h post elicitation. MeJA did not effect phosphoprotein accumulation but conditioning led to the potentiation and differential induction of phosphoproteins due to chitosan and elicitor. The results indicate that cells are sensitized by the exposure to MeJa to respond more intensely and rapidly toward secondary elicitation by fungal pathogen derived elicitors.

Synthesis and evaluation of 4-(3-methyl-2-butenoxy) isonitrosoacetophenone, a radiation-induced stress metabolite in Citrus.

The time- and dose-dependent occurrence of 4-(3-methyl-2-butenoxy)isonitrosoacetophenone, a gamma-irradiation-induced stress metabolite was investigated. The chemical synthesis of the compound is reported. The compound exhibits antifungal activity, as well as antioxidant activity, as indicated by its ability to scavenge reactive oxygen radicals in a chemiluminescence assay.