Biomedical subjects

Consuelo M De Moraes

Publications and source records attributed to Consuelo M De Moraes.

7 recordsLinked to original sources

PubMed2007

Jasmonate, salicylate, and benzoate in insect eggs.

Jasmonic acid (JA) and salicylic acid (SA) are key molecules in the initiation of plant defensive responses to attack by herbivores and pathogens, respectively. Our previous work has shown that JA occurs at high concentrations in eggs and neonates of lepidopteran species. Here, we extend our analyses to eggs of 15 non-lepidopteran insect species spanning eight orders, again screening for JA, but also including SA and one of its metabolic precursors, benzoic acid. We detected all three compounds in eggs of almost all the species examined. Moreover, concentrations of these compounds were variable across species, suggesting that species accumulate and/or utilize the compounds differently. Eggs of the fruit-feeding fly Rhagoletis pomonella contained the greatest concentrations of all three compounds, which appear to be common in fruit. The presence of these plant-derived compounds in eggs may serve defensive or other functions for insects, and could conceivably trigger plant defensive responses after oviposition.

Animals↗

PubMed2006

Volatile chemical cues guide host location and host selection by parasitic plants.

The importance of plant volatiles in mediating interactions between plant species is much debated. Here, we demonstrate that the parasitic plant Cuscuta pentagona (dodder) uses volatile cues for host location. Cuscuta pentagona seedlings exhibit directed growth toward nearby tomato plants (Lycopersicon esculentum) and toward extracted tomato-plant volatiles presented in the absence of other cues. Impatiens (Impatiens wallerana) and wheat plants (Triticum aestivum) also elicit directed growth. Moreover, seedlings can distinguish tomato and wheat volatiles and preferentially grow toward the former. Several individual compounds from tomato and wheat elicit directed growth by C. pentagona, whereas one compound from wheat is repellent. These findings provide compelling evidence that volatiles mediate important ecological interactions among plant species.

Cues↗

PubMed2006

Jasmonate in lepidopteran larvae.

Jasmonic acid (JA) is a key molecule initiating plant defensive responses to herbivory. Our previous work has shown that this phytohormone is often present at high concentrations in eggs and neonates of lepidopteran species. In this work, we document the concentrations of JA found in various tissues of larval H. virescens fed on artificial diets with varying JA concentrations and on transgenic tobacco lines with different capabilities of producing JA. At high JA concentrations, excess jasmonate appeared to be voided in frass, but significant amounts were found in most larval tissues we analyzed as well as in regurgitant. At lower concentrations, caterpillars excreted less JA and appeared to accumulate relatively greater amounts of JA in their tissues. In both experiments, substantial amounts of JA were found in labial salivary glands, a notable result since JA is an important signaling molecule involved in the induction of plant defenses.

Animals↗

PubMed2006

Effects of genetic modification on herbivore-induced volatiles from maize.

Large-scale implementation of transgenic crop varieties raises concerns about possible nontarget effects on other organisms. This study examines the effects of genetic modification on plant volatile production and its potential impact on arthropod population dynamics. We compared herbivore-induced volatile emissions from Bacillus thuringiensis Berliner (Bt) maize plants to those from a nontransformed isoline following exposure to various types of leaf damage. When equal numbers of Helicoverpa zea Boddie (Lepidoptera: Noctuidae) larvae fed on Bt and non-Bt maize, volatile emissions were significantly lower in the transgenic plants, which also exhibited less leaf damage. When damage levels were controlled by adding more larvae to Bt plants, the plants' volatile emissions increased but displayed significant differences from those of nontransgenic plants. Significantly higher amounts of linalool, beta-myrcene, and geranyl acetate were released from transgenic maize than from non-Bt plants. Manipulating the duration of feeding by individual larvae to produce similar damage patterns resulted in similar volatile profiles for Bt and non-Bt plants. Controlling damage levels more precisely by mechanically wounding leaves and applying larval regurgitant likewise resulted in similar emission patterns for Bt and non-Bt maize. Overall, changes in the herbivore-induced volatile profiles of Bt maize appeared to be a consequence of altered larval feeding behavior rather than of changes in biochemical plant defense pathways. The implications of these findings for understanding the impacts of plant-mediated cues on pest and natural enemy behavior in transgenic crop systems are discussed.

Animals↗

PubMed2005

Jasmonate in lepidopteran eggs and neonates.

Jasmonic acid (JA) is a key molecule initiating plant defensive responses to attack by pathogens and herbivores. This phytohormone is produced at sites of insect damage and is ingested by feeding insects, but its subsequent occurrence in insect tissues remains to be studied. We report the presence of JA in eggs and neonates of all nine lepidopteran species that we screened, representing four superfamilies and five families of Lepidoptera. Concentrations of JA in some lepidopteran species far exceeded those found in most plant species. Levels of JA varied significantly among species and between eggs and neonates of the same species. In some cases, eggs contained significantly more JA than neonates, but for at least one species (Lymantria dispar) neonates had more JA than their eggs despite lacking food upon emergence. The presence of JA in eggs and neonates across a wide taxonomic range may indicate that JA has an undescribed function in insects.

Animals↗

PubMed2004

Biochemical crypsis in the avoidance of natural enemies by an insect herbivore.

Plant-herbivore interactions provide well studied examples of coevolution, but little is known about how such interactions are influenced by the third trophic level. Here we show that larvae of the specialized lepidopteran herbivore Heliothis subflexa reduce their vulnerability to natural enemies through adaptation to a remarkable and previously unknown feature of their host plant, Physalis angulata: The fruits of this plant lack linolenic acid (LA), which is required for the development of most insects. By overcoming this nutritional deficiency, H. subflexa larvae achieve numerous advantages. First, they gain near-exclusive access to a food resource: we demonstrate that closely related Heliothis virescens larvae cannot develop on P. angulata fruit unless the fruit are treated with LA. Second, they reduce their vulnerability to enemies: LA is a key component of volicitin, an elicitor of plant-volatile-signaling defenses. We demonstrate that volicitin is absent in the oral secretions of fruit-feeding caterpillars, that the volatile profiles of plants induced by fruit feeding differ from those induced by leaf feeding or by feeding on LA-treated fruit, and that the former are far less attractive to female Cardiochiles nigriceps parasitoids. Finally, they render themselves nutritionally unsuitable as hosts for enemies that require LA for their own development: we show that C. nigriceps larvae fail to develop within the bodies of fruit-feeding caterpillars but do develop in caterpillars feeding on LA-treated fruit. Thus, H. subflexa larvae not only overcome a serious dietary deficiency but also reduce their vulnerability to natural enemies through a form of "biochemical crypsis."

Animal Feed↗

PubMedDate not supplied

Induced plant signaling and its implications for environmental sensing.

The sophisticated chemical responses of plants to environmental stimuli have profound implications for the development of remote sensing systems. Recent advances in the investigation of these responses have demonstrated that plants can be developed as reliable reporters of numerous environmental stimuli including soil and water conditions, light levels, temperature, mechanical damage, insect feeding, exposure to pathogens--including those that affect animals and humans--and exposure to airborne chemicals. Researchers are just beginning to understand the full range of plant phenotypic responses to these and other stimuli. These responses often have measurable physiological and molecular components that are readily observed. Other responses (e.g., internal biochemical changes) are less readily assayed, although sensing devices are being developed. Plant volatile emission "signatures" are particularly promising modes of plant reporting that can provide highly specific information regarding a diverse range of environmental variables on short time scales, but new approaches are needed for sensing these responses remotely. Modern molecular techniques promise to allow us to refine plant sensing and reporting, greatly enhancing the potential utility of plants as "sentinels." Continued basic research aimed at characterizing the physiological, biochemical, and molecular responses of plants to environmental stimuli (including airborne chemicals, insects and pathogenic microbes) are essential to achieving that promise.

Environmental Monitoring↗