Submitted to: Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/22/2006
Publication Date: 10/17/2006
Citation: Dombrowski, J.E., Bergey, D.R. 2006. Calcium ions enhance systemin activity and play an integral role in the wound response. Plant Science. V172 P 335-344.
Interpretive Summary: Plants respond to mechanical wounding or herbivorous insect attack by inducing the synthesis of a wide array of defense related proteins at the wound site and systemically throughout the plant. In solanaceous plants wounding causes the release and mobilization of an 18 amino acid polypeptide called systemin, which has been shown to be a potent inducer of the wound response. Calcium is a ubiquitous signal in all plant tissues involved in mediating responses to environmental or developmental stimuli. The specific biological role of calcium in the wound response signaling cascade is unclear. The research presented in this manuscript demonstrated that calcium ions are an integral part of the wound and systemin signaling pathways. Furthermore, calcium and magnesium ions sensitize leaf cells for systemin. Taken together this data provides valuable insight into potential roles and mechanisms divalent cations play in mediating the wound response in plants.
Technical Abstract: Calcium is an important component of the signaling network mediating plant responses to a wide array of environmental or developmental stimuli. In this report we have investigated the effects of calcium and other divalent cations on the wound response in tomato plants. Treatment of plants with calcium ionophores, ionomycin and A23187, induced accumulation of proteinase inhibitors, and this induction was blocked in the mutant def-1, which is compromised in octadecanoid pathway and wound response signaling. Calcium transport antagonists (nifedipine, verapamil, ruthenium red, and erythrosine-B) inhibited proteinase inhibitor synthesis in response to wounding. Erythrosine-B also blocked proteinase inhibitor induction by the wound signaling peptide systemin, and the volatile elicitor methyljasmonate, whereas the calcium channel blocker ruthenium red had no effect. Calcium chelators induced the synthesis of proteinase inhibitors in a jasmonic acid-dependent and systemin-independent manner. Calcium and magnesium ions enhanced systemin activity by decreasing the concentration of systemin necessary to induce maximal proteinase inhibitor accumulation by 100 fold. Taken together, the data showed that calcium ions are an integral part of the wound and systemin signaling pathways. Furthermore, calcium and magnesium ions sensitize leaf cells for systemin by an, as yet unknown mechanism.