Assessment of stress-related enzymes in response to either exogenous salicylic acid or methyl jasmonate in Jatropha curcas L. leaves, an attractive plant to produce biofuel

• Stress-related enzymes are differentially regulated by MeJA and SA.
• Both signaling routes seem to be operating independently.
• The results presented here add new light on J. curcas defense mechanisms.

The responsiveness of specific enzymes, involved with antioxidant and defensive mechanisms, were evaluated in leaf tissue extracts of Jatropha curcas L. (J. curcas) seedlings treated with different amounts of methyl jasmonate (MeJA [0.1, 10 and 100 μM]) or salicylic acid (AS [1, 5 and 10 mM]). In addition, the enzymes activities were measured 24 and 48 h after each stimulus. The positive effect of lower amounts of MeJA on the catalase (CAT) activity was more prominent during the first 24 h, by contrast higher concentration of MeJA (100 μM) provoked a reduction of CAT activity in both periods tested. On the other hand, CAT activity increased upon all SA treatments. The guaiacol peroxidase (GPX) activity was incremented in response to both stimuli, while the ascorbate peroxidase (APX) had contrasting responses regarding different concentration of MeJA and SA. The activity of superoxide dismutase (SOD) was not altered in response to any treatment. Chitinase activity was induced in higher degree in response to MeJA 100 μM after 24 and 48 h exposure, whereas under SA treatments it showed a quite discrete induction throughout experiments. The activity of β-1,3-glucanase (GLU) in response to MeJA was positively affected in all concentration only after 48 h treatment, while in response to SA it showed induction for 2 tested concentration (1 and 5 mM) during the first 24 h. However at time of 48 h treatment only 5 mM was effective to induce this particular enzyme. With regard to phenylalanine ammonia-lyase (PAL) activity, it was only induced by SA treatments. Collectively, our results indicate that MeJA and SA can act differentially on most tested enzymes reflecting preferential pathways routes regulating such activities in our model plant.