Early signaling network in tobacco cells elicited with methyl jasmonate and cyclodextrins

Abstract

We analyze, for the first time, the early signal transduction pathways triggered by methyl jasmonate (MJ) and cyclodextrins (CDs) in tobacco (Nicotiana tabacum) cell cultures, paying particular attention to changes in cytosolic free Ca(2+) concentration ([Ca(2+)](cyt)), the production of hydrogen peroxide (H(2)O(2)) and nitric oxide (NO), and late events like the induction of capsidiol. Our data indicate that MJ and CDs trigger a [Ca(2+)](cyt) rise promoted by Ca(2+) influx through Ca(2+)-permeable channels. The joint presence of MJ and CDs provokes a first increase in [Ca(2+)](cyt) similar to that observed in MJ-treated cells, followed by a second peak similar to that found in the presence of CDs alone. Moreover, oxidative burst induced by MJ is more pronounced when tobacco cells are incubated with CDs alone or in combination with MJ. The presence of both elicitors provokes H(2)O(2) production similar to that found in CD-treated cells, and a sustained response similar to that found in MJ-treated cells. In all treatments, H(2)O(2) production is dependent on Ca(2+) influx and protein phosphorylation events. Similarly, the joint action of both elicitors provokes NO accumulation, although to a lesser extent that in MJ-treated cells because CDs alone do not trigger this accumulation. This NO production is dependent on Ca(2+) influx but independent of both H(2)O(2) production and staurosporine-sensitive phosphorylation events. Taken as a whole, these results suggest the existence of different intracellular signaling pathways for both elicitors. Likewise, CDs might act by regulating the signaling pathway triggered by MJ since, in the presence of both compounds, CDs neutralize the strong oxidative and nitrosative bursts triggered by MJ and therefore, they regulate both H(2)O(2) and NO levels.