Exogenous jasmonates simulate insect wounding in tomato plants (Lycopersicon esculentum) in the laboratory and field

Abstract

Wounding increases the levels and activities of several defense-related proteins in the foliage of the tomato plant,Lycopersicon esculentum Mill. Evidence indicates that two of these responses, the systemic increases in polyphenol oxidase and proteinase inhibitors, are regulated by an octadecanoid-based signalling pathway which includes the wound hormone, jasmonic acid. It is not known whether other responses to wounding are also regulated by this same signalling pathway. In this paper, we show that application of jasmonates (jasmonic acid or its volatile derivative, methyl jasmonate) in low concentrations to foliage of young tomato plants induced, in a dose-dependent manner, the same protein responses-polyphenol oxidase, proteinase inhibitors, lipoxygenase, and peroxidase-as doesHelicoverpa zea Boddie feeding. Application of jasmonic acid to a single leaflet of four-leaf tomato plants induced these four proteins in a spatial pattern nearly identical to that produced by localized feeding ofH. zea. Exogenous jasmonic acid also decreased suitability of foliage for the beet armyworm,Spodoptera exigua Hubner in the laboratory. Based on these results, we conducted an experiment to measure the effects of jasmonic acid spray under field conditions. We provide the first evidence that jasmonic acid spray on field plants induces production of chemical defenses above the levels found in unsprayed controls. Exogenous jasmonic acid sprayed on plants in agricultural plots increased levels of polyphenol oxidase and proteinase inhibitors. Because application of jasmonic acid induces these defensive compounds at low concentrations in a manner similar to natural wounding, it may prove to be a useful tool for stimulating plant resistance to insects in the field.

Differential Activity of Peroxidase Isozymes in Response to Wounding, Gypsy Moth, and Plant Hormones in Northern Red Oak (Quercus rubra L.)

“…In addition, generalized soluble or wall-bound POD activity increases in other plant species in response to wounding (Birecka and Miller, 1974;Kawaoka et al, 1994), pathogens (Bashan et al, 1987), salicylic acid (Rao et al, 1997), and jasmonates (Thaler et al, 1996;Moore et al, 2003). While JA and insect wounding have been found to elevate total soluble POD activity similarly (Choi et al, 1994;Tamari et al, 1995;Zhang and Baldwin, 1997), this study is among the first to suggest that various peroxidase isozymes may be differentially responsive to JA or other signals (Buzi et al, 2004) and the first to find insectresponsive POD isoforms.…”

“…The spraying procedure was identical to that of the JA treatment. Both spray regimes were chosen to be consistent with other studies assessing the impact of these signals on enzymatic and metabolic activity and transcript abundance of defense-related genes (e.g., Thaler et al, 1996;Zhang and Baldwin, 1997;Cipollini and Redman, 1999;Moore et al, 2003).…”

Intraspecific variation in defense against a generalist lepidopteran herbivore in populations of Eruca sativa (Mill.)

“…(1996), PI activity was calculated as the percentage of trypsin activity relative to controls (Thaler et al. 1996). …”

Constitutive and inducible trypsin proteinase inhibitor production incurs large fitness costs in Nicotiana attenuata

“…2 and 3) have exploited inducible expression as a means of controlling for, or homogenizing, the genetic background of plants and have measured plant fitness before and after eliciting resistance in plants in herbivore-free environments. The discovery that herbivore attack elicits the JA cascade in many species, and that exogenous JA treatments elicits induced resistance without the wounding that normally accompanies herbivore attack, has motivated studies to measure the fitness costs of JA-induced responses (1,10,(26)(27)(28)(29). However, because of pleiotropic effects of the elicitors, the observed fitness differences do not arise solely from the expression of the resistant trait (12,30), and therefore these studies are likely to overestimate the fitness costs of resistance.…”