Biomedical subjects

André Kessler

Publications and source records attributed to André Kessler.

7 recordsLinked to original sources

PubMed2006

Priming of plant defense responses in nature by airborne signaling between Artemisia tridentata and Nicotiana attenuata.

Plants release volatile organic compounds (VOCs) in response to wounding and herbivore attack, some of which trigger responses in neighboring unattacked plants in the laboratory under conditions that are not likely to occur in the real world. Whether plants 'eavesdrop' on the volatile emissions of their neighbors in nature is not known. The best documented field study of between-species signaling via above-ground VOCs involves increases in fitness parameters of native tobacco (Nicotiana attenuata) transplanted adjacent to clipped sagebrush (Artemesia tridentata tridentata). Clipped sagebrush releases many biologically active VOCs, including methyl jasmonate (MeJA), methacrolein and a series of terpenoid and green leaf VOCs, of which MeJA, while active under laboratory conditions, is not released in sufficient quantities to directly elicit induced resistance in the field. Here we demonstrate, with laboratory and field-based experiments, that priming (rather than direct elicitation) of native N. attenuata's induced chemical defenses by a sagebrush-released VOC bouquet can account for earlier findings. With microarrays enriched in N. attenuata herbivore-regulated genes, we found transcriptional responses in tobacco growing adjacent to clipped sagebrush foliage, but failed to detect the direct elicitation of defensive chemicals or proteins. However, we observed an accelerated production of trypsin proteinase inhibitors when Manduca sexta caterpillars fed on plants previously exposed to clipped sagebrush. This readying of a defense response, termed priming, results in lower total herbivore damage to plants exposed to clipped sagebrush and in a higher mortality rate of young Manduca caterpillars. Our study demonstrates priming of plant defense responses as a mechanism of plant-plant signaling in nature, and provides an example for the analysis of between-plant signaling under ecologically realistic conditions. Although we describe priming as a potential mechanism for signaling between plants in nature, we critically discuss the ecological relevance of the particular interaction.

Animals↗

PubMed2004

Silencing the jasmonate cascade: induced plant defenses and insect populations.

We transformed the native tobacco, Nicotiana attenuata, to silence its lipoxygenase, hydroperoxide lyase, and allene oxide synthase genes in order to inhibit oxylipin signaling, known to mediate the plant's direct and indirect defenses. When planted into native habitats, lipoxygenase-deficient plants were more vulnerable to N. attenuata's adapted herbivores but also attracted novel herbivore species, which fed and reproduced successfully. In addition to highlighting the value of genetically silencing plants to study ecological interactions in nature, these results show that lipoxygenase-dependent signaling determines host selection for opportunistic herbivores and that induced defenses influence herbivore community composition.

Acetates↗

PubMed2004

Solanum nigrum: a model ecological expression system and its tools.

Plants respond to environmental stresses through a series of complicated phenotypic responses, which can be understood only with field studies because other organisms must be recruited for their function. If ecologists are to fully participate in the genomics revolution and if molecular biologists are to understand adaptive phenotypic responses, native plant ecological expression systems that offer both molecular tools and interesting natural histories are needed. Here, we present Solanum nigrum L., a Solanaceous relative of potato and tomato for which many genomic tools are being developed, as a model plant ecological expression system. To facilitate manipulative ecological studies with S. nigrum, we describe: (i) an Agrobacterium-based transformation system and illustrate its utility with an example of the antisense expression of RuBPCase, as verified by Southern gel blot analysis and real-time quantitative PCR; (ii) a 789-oligonucleotide microarray and illustrate its utility with hybridizations of herbivore-elicited plants, and verify responses with RNA gel blot analysis and real-time quantitative PCR; (iii) analyses of secondary metabolites that function as direct (proteinase inhibitor activity) and indirect (herbivore-induced volatile organic compounds) defences; and (iv) growth and fitness-estimates for plants grown under field conditions. Using these tools, we demonstrate that attack from flea beetles elicits: (i) a large transcriptional change consistent with elicitation of both jasmonate and salicylate signalling; and (ii) increases in proteinase inhibitor transcripts and activity, and volatile organic compound release. Both flea beetle attack and jasmonate elicitation increased proteinase inhibitors and jasmonate elicitation decreased fitness in field-grown plants. Hence, proteinase inhibitors and jasmonate-signalling are targets for manipulative studies.

Animals↗

PubMed2004

Herbivore-induced plant vaccination. Part I. The orchestration of plant defenses in nature and their fitness consequences in the wild tobacco Nicotiana attenuata.

A plant's responses to attack from particular pathogens and herbivores may result in resistance to subsequent attack from the same species, but may also affect different species. Such a cross-resistance, called immunization or vaccination, can benefit the plant, if the fitness consequences of attack from the initial attacker are less than those from subsequent attackers. Here, we report an example of naturally occurring vaccination of the native tobacco plant, Nicotiana attenuata, against Manduca hornworms by prior attack from the mirid bug, Tupiocoris notatus (Dicyphus minimus), which results from the elicitation of two categories of induced plant responses. First, attack from both herbivore species causes the plants in nature to release predator-attracting volatile organic compounds (VOCs), and the attracted generalist predator, Geocoris pallens, preferentially attacks the less mobile hornworm larvae. Second, attack from both mirids and hornworms increases the accumulation of secondary metabolites and proteinase inhibitors (PIs) in the leaf tissue, which is correlated with the slow growth of Manduca larvae. Mirid damage does not significantly reduce the fitness of the plant in nature, whereas attack from the hornworm reduces lifetime seed production. Consequently, plants that are attacked by mirids realize a significant fitness advantage in environments with both herbivores. The combination of growth-slowing direct defenses and predator-attracting indirect defenses results in greater hornworm mortality on mirid-attacked plants and provides the mechanism of the vaccination phenomenon.

Animals↗

PubMed2003

Attracting friends to feast on foes: engineering terpene emission to make crop plants more attractive to herbivore enemies.

When attacked by herbivorous insects or mites, some plant species call on other arthropods for help. They emit mixtures of volatile compounds, dominated by terpenes, to attract carnivorous arthropods that prey on or parasitise herbivores and so reduce further damage. This fascinating defence strategy offers a new, environmentally friendly approach to crop protection. Using recent advances in the biochemistry and molecular genetics of terpene biosynthesis, it should now be possible to engineer crop plants that release terpenes for attracting herbivore enemies. By introducing or selectively altering the existing rate of terpene emission and composition, plant breeders could enable attacked plants to attract enemies and reduce additional herbivory, without compromising the effectiveness of other modes of defence.

Animals↗

PubMed2002

Volatile signaling in plant-plant-herbivore interactions: what is real?

Plants release volatiles after herbivore attack in a highly regulated fashion. These compounds attract natural enemies and function as indirect defenses. Whether neighboring plants 'eavesdrop' on these volatile signals and tailor their defenses accordingly remains controversial. Recent laboratory studies have identified transcriptional changes that occur in plants in response to certain volatiles. These changes occur under conditions that enhance the probability of signal perception and response. Field studies have demonstrated repeatable increases in the herbivore resistance of plants growing downwind of damaged plants.

Animals↗

PubMed2002

Plant responses to insect herbivory: the emerging molecular analysis.

Plants respond to herbivore attack with a bewildering array of responses, broadly categorized as direct and indirect defenses, and tolerance. Plant-herbivore interactions are played out on spatial scales that include the cellular responses, well-studied in plant-pathogen interactions, as well as responses that function at whole-plant and community levels. The plant's wound response plays a central role but is frequently altered by insect-specific elicitors, giving plants the potential to optimize their defenses. In this review, we emphasize studies that advance the molecular understanding of elicited direct and indirect defenses and include verifications with insect bioassays. Large-scale transcriptional changes accompany insect-induced resistance, which is organized into specific temporal and spatial patterns and points to the existence of herbivore-specific trans-activating elements orchestrating the responses. Such organizational elements could help elucidate the molecular control over the diversity of responses elicited by herbivore attack.

Animals↗