Rapid defense responses in maize leaves induced by Spodoptera exigua caterpillar feeding

ABSTRACTInsects such as beet armyworm caterpillars (Spodoptera exigua) cause extensive damage to maize (Zea mays) by consuming foliar tissue. Maize plants respond to such insect attack by triggering defense mechanisms that involve large changes in gene expression and the biosynthesis of specialized metabolites and defense signaling molecules. To investigate dynamic maize responses to herbivore feeding, leaves of maize inbred line B73 were infested with S. exigua caterpillars for 1 to 24 hours, followed by comprehensive transcriptomic and metabolomic characterization. Our results show that the most significant gene expression responses of maize to S. exigua feeding occur at early time points, within 4 to 6 hours after caterpillar infestation. However, both gene expression and metabolite profiles continued changing during the entire 24-hour experiment while photosynthesis genes were gradually decreased. The primary and specilaze metabolism shift maught be temporal and dynamic processes in the infested leaf tissue. We analyzed the effects of mutating genes in two major defense-related pathways, benzoxazinoids (Bx1 and Bx2) and jasmonic acid (Lox8), using Dissociation (Ds) transposon insertions in maize inbred line W22. Together, these results show that maize leaves shift to implementation of chemical defenses within one hour after the initiation of caterpillar attack. Thus, the induced biosynthesis of specialized metabolites can have major effects in maize-caterpillar interactions.HIGHLIGHTA comprehensive transcriptic and metabolomic profiling time course of maize foliar responses to caterpillar feeding identifies genes for the synthesis of benzoxazinoids and phytohormones.

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Caterpillar salivary enzymes: "eliciting" a response

Phytoprotection ◽

10.7202/008904ar ◽

2004 ◽

Vol 85 (1) ◽

pp. 33-37 ◽

Cited By ~ 14

Author(s):

Magali Merkx-Jacques ◽

Jacqueline C. Bede

Keyword(s):

Artificial Diet ◽

Spodoptera Exigua ◽

Induced Defense ◽

Defense Responses ◽

Beet Armyworm ◽

Herbivorous Insect ◽

Plant Responses ◽

Plant Defense Responses ◽

Induced Defense Responses ◽

Bertha Armyworm

Abstract Plants exhibit remarkable plasticity in their ability to differentiate between herbivorous insect species and subtly adjust their defense responses to target distinct pests. One key mechanism used by plants to recognize herbivorous caterpillars is elicitors present in their oral secretions; however, these elicitors not only cause the induction of plant defenses but recent evidence suggests that they may also suppress plant responses. The absence of “expected changes” in induced defense responses of insect-infested plants has been attributed to hydrogen peroxide produced by caterpillar salivary glucose oxidase (GOX). Activity of this enzyme is variable among caterpillar species; it was detected in two generalist caterpillars, the beet armyworm (Spodoptera exigua) and the bertha armyworm (Mamestra configurata), but not in other generalist or specialist caterpillar species tested. In the beet armyworm, GOX activity fluctuated over larval development with high activity associated with the salivary glands of fourth instars. Larval salivary GOX activity of the beet armyworm and the bertha armyworm was observed to be significantly higher in caterpillars reared on artificial diet as compared with those reared on Medicago truncatula plants. This implies that a factor in the diet is involved in the regulation of caterpillar salivary enzyme activity. Therefore, plant diet may be regulating caterpillar oral elicitors that are involved in the regulation of plant defense responses: our goal is to understand these two processes.

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Can herbivore-induced volatiles protect plants by increasing the herbivores’ susceptibility to natural pathogens?

10.1101/317560 ◽

2018 ◽

Cited By ~ 3

Author(s):

Laila Gasmi ◽

María Martínez-Solís ◽

Ada Frattini ◽

Meng Ye ◽

María Carmen Collado ◽

...

Keyword(s):

Gut Microbiota ◽

Spodoptera Exigua ◽

Negative Impact ◽

Insect Herbivory ◽

Defense Responses ◽

Hexenyl Acetate ◽

Induced Volatiles ◽

Herbivore Induced Plant Volatiles ◽

Herbivore Induced Volatiles ◽

Gut Microbiota Composition

AbstractIn response to insect herbivory, plants mobilize various defenses. Defense responses include the release of herbivore-induced plant volatiles (HIPVs) that can serve as signals to alert undamaged tissues and to attract natural enemies of the herbivores. It has also been shown that some HIPVs can have a direct negative impact on herbivore survival, but it is not yet understood by what mechanism. Here we tested the hypothesis that exposure to HIPVs renders insects more susceptible to natural pathogens. Exposing caterpillars of the noctuid Spodoptera exigua to indole and linalool, but not exposure to (Z)-3-hexenyl acetate increased the susceptibility to its nucleopolyhedrovirus (SeMNPV). We also found that exposure to indole, but not exposure to linalool or (Z)-3-hexenyl acetate, increased the pathogenicity of Bacillus thuringiensis. Additional experiments revealed significant changes on gut microbiota composition after forty-eight hours of larval exposure to indole. Overall, these results provide evidences that certain HIPVs can strongly enhance the susceptibility of caterpillars to pathogens, possibly through effects on the insects’ gut microbiota. These findings suggest a novel mechanism by which HIPVs can protect plants from herbivorous insects.

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