Flaming a tomato leaf evokes a variation potential; excising an unwounded leaf evokes an action potential; while excising a wounded leaf 90 sec after flame-wounding evokes an action potential superimposed on the variation potential. Furthermore, flaming one leaf induces rapid (15 min), systemic and biphasic accumulation of CMBP transcript, excising the unwounded leaf causes slower, monophasic transcript accumulation, while excising the wounded leaf after 90 sec has no effect on CMBP transcript accumulation in response to the flame-wound. We propose that both of these electrical signals, the flame-evoked variation potential and the cut-wound evoked action potential are capable of inducing CMBP transcript accumulation, although with somewhat different kinetics. Earlier work by others found the cut-wound had no effect on pin transcript accumulation, thus leaf excision could be used as a tool to determine whether transport of wound hormones out of the leaf could trigger pin gene expression. Here, however, leaf excision could not be used to prevent signal transmission, since excision itself evoked an electrical signal and transcript accumulation. Instead, the results show that two different electrical signals are involved in rapid, systemic CMBP mRNA accumulation and their effects are not additive implying they may share some common aspects.
Keywords: action potential; signal transmission; tomato; variation potential; wounding.