As a first step towards developing a genetic system for investigating
signaling processes in plants, we have developed a screen for signalin
g mutants deficient in a wound response. We have isolated two mutants
of tomato that lack detectable production of proteinase inhibitors ind
uced systemically in leaves by wounding. The mutants are deficient in
the induction of both proteinase Inhibitor I and proteinase Inhibitor
II but can be induced to respond at near wild-type levels by methyl ja
smonate, a known elicitor of inhibitor production in tomato. While com
pletely deficient in systemic production of proteinase inhibitors, bot
h mutants produce some proteinase inhibitor in wounded leaves. This ev
idence suggests the existence of two signaling pathways, one local and
one systemic, that regulate the induction of proteinase inhibitor syn
thesis in response to wounding.