The pathway for systemic electrical signal conduction in the wounded tomato plant

Abstract

Abstract. The pathway of a systemic electrical signal possibly linking wounding and the systemic synthesis of proteinase inhibitor was investigated in tomato (Lycopersicon esculentum Mill. cv. Moneymaker) plants. Heat, causing wounding to a cotyledon, was used to induce both a travelling electrical signal and systemic proteinase inhibitor activity. Intracellular recordings of changes in the membrane potential of different cell types were measured in the petiole of leaf 1, the first true leaf, and impaled cells were identified by injection of fluorescent dye (Lucifer Yellow CH). No difference was found between the membrane potentials of the different cell types; the mean membrane potential of all the cell types was -148 _+ 3 mV. Only sieve-tube elements and companion cells produced large (79 _ 3.3 mV) action-potential-like depolarisations following wounding, although smaller (23 + 1.6 mV) depolarisations were observed in other cell types. It was concluded that the electrical signal possibly linking a wound stimulus in a cotyledon with the induction of systemic proteinase inhibitor synthesis was propagated in the sieve-tube element/companion cell complex.

Plant- and stimulus-specific variations in remote-controlled sieve-tube occlusion

“…15 EPWs are generated by mechanical and physical stimuli [16][17][18] and depend on voltage-activated and possibly mechanosensitive channels along sieve tubes. 14,19 Our recent study 13 showed, that forisomes at 3-4 cm from the stimulus site dispersed 15-45 sec after burning the leaf tip.…”

Reversible Calcium-Regulated Stopcocks in Legume Sieve Tubes [W]

“…Cytoplasmic Ca 2ϩ rises sharply during these action potentials (Kikuyama and Tazawa, 1983;Thiel et al, 1997). In higher plants, similar potential waves are transmitted along sieve tubes (Eschrich et al, 1988;Fromm, 1991;Rhodes et al, 1996), where they seem to raise levels of cytoplasmic Ca 2ϩ (Fromm and Spanswick, 1993). It seems a reasonable working hypothesis that exogenously induced turgor changes trigger membrane potential waves in SEs that are accompanied by intracellular Ca 2ϩ surges.…”

A Gene Encoding a Chloroplast-Targeted Lipoxygenase in Tomato Leaves Is Transiently Induced by Wounding, Systemin, and Methyl Jasmonate

“…A phloem mobile polypeptide called systemin behaves as a systemic signal released from wound sites (Pearce et al, 1991;McGurl et al, 1992McGurl et al, , 1994Narvaez-Vasquez et al, 1995), but severa1 other chemicals, including IAA (Thornburg and Li, 1990), ABA (PeAa-Cortés et al, 1989), and ethylene (ODonnell et al, 1996), have been associated with the signaling pathway and with physical forces such as hydraulic effects (Malone and Alarcon, 1995) and action potentials (Herde et al, 1996;Rhodes et al, 1996;Stankovic and Davies, 1996).…”