Ga. Howe et al., AN OCTADECANOID PATHWAY MUTANT (JL5) OF TOMATO IS COMPROMISED IN SIGNALING FOR DEFENSE AGAINST INSECT ATTACK, The Plant cell, 8(11), 1996, pp. 2067-2077
The activation of defense genes in tomato plants has been shown to be
mediated by an octadecanoic acid-based signaling pathway in response t
o herbivore attack or other mechanical wounding, We report here that a
tomato mutant (JL5) deficient in the activation of wound-inducible de
fense genes is also compromised in resistance toward the lepidopteran
predator Manduca sexta (tobacco hornworm), Thus, we propose the name d
efenseless1 (def1) for the mutation in the JL5 line that mediates this
altered defense response. In experiments designed to define the norma
l function of DEF1, we found that def1 plants are defective in defense
gene signaling initiated by prosystemin overexpression in transgenic
plants as well as by oligosaccharide (chitosan and polygalacturonide)
and polypeptide (systemin) elicitors. Supplementation of plants throug
h their cut stems with intermediates of the octadecanoid pathway indic
ates that def1 plants are affected in octadecanoid metabolism between
the synthesis of hydroperoxylinolenic acid and 12-oxo-phytodienoic aci
d. Consistent with this defect, def1 plants are also compromised in th
eir ability to accumulate jasmonic acid, the end product of the pathwa
y, in response to wounding and the aforementioned elicitors. Taken tog
ether, these results show that octadecanoid metabolism plays an essent
ial role in the transduction of upstream wound signals to the activati
on of antiherbivore plant defenses.