The in vivo analysis of a pathogen is a critical step in gaining greater knowledge of pathogen biology and host-pathogen interactions. In the last two decades, there has been a notable rise in the number of studies on developing insects as a model for studying pathogens, which provides various benefits, such as ethical acceptability, relatively short life cycle, and cost-effective care and maintenance relative to routinely used rodent infection models. Furthermore, lepidopteran insects provide many advantages, such as easy handling and tissue extraction due to their large size relative to other invertebrate models, like Caenorhabditis elegans. Additionally, insects have an innate immune system that is highly analogous to vertebrates. In the present review, we discuss the components of the insect's larval immune system, which strengthens its usage as an alternative host, and present an updated overview of the research findings involving lepidopteran insects (Galleria mellonella, Manduca sexta, Bombyx mori, and Helicoverpa armigera) as infection models to study the virulence by enteropathogens due to the homology between insect and vertebrate gut.
The late 5th instar caterpillar of the cecropia silk moth (Hyalophora cecropia) spins a silken cocoon with a distinct, multilayered architecture. The cocoon construction program, first described by the seminal work of Van der Kloot and Williams, consists of a highly ordered sequence of events. We perform behavioral experiments to re-evaluate the original cecropia work, which hypothesized that the length of silk that passes through the spinneret controls the orderly execution of each of the discrete events of cocoon spinning. We confirm and extend by three-dimensional scanning and quantitative measurements of silk weights that if cocoon construction is interrupted, upon re-spinning, the caterpillar continues the cocoon program from where it left off. We also confirm and extend by quantitative measurements of silk weights that cecropia caterpillars will not bypass any of the sections of the cocoon during the construction process, even if presented with a pre-spun section of a cocoon spun by another caterpillar. Blocking silk output inhibits caterpillars from performing normal spinning behaviors used for cocoon construction. Surprisingly, unblocking silk output 24-hr later did not restart the cocoon construction program, suggesting the involvement of a temporally-defined interval timer. We confirm with surgical reductions of the silk glands that it is the length of silk itself that matters, rather than the total amount of silk extracted by individuals. We used scanning electron microscopy to directly show that either mono- or dual-filament silk (i.e., equal silk lengths but which vary in their total amount of silk extracted) can be used to construct equivalent cocoons of normal size and that contain the relevant layers. We propose that our findings, taken together with the results of prior studies, strongly support the hypothesis that the caterpillar uses a silk "odometer" to measure the length of silk extracted during cocoon construction but does so in a temporally regulated manner. We further postulate that our examination of the anatomy of the silk spinning apparatus and ablating spinneret sensory output provides evidence that silk length measurement occurs upstream of output from the spinneret.
- MeSH
- Biobehavioral Sciences MeSH
- Metamorphosis, Biological physiology MeSH
- Bombyx anatomy & histology physiology MeSH
- Behavior, Animal physiology MeSH
- Sensation physiology MeSH
- Silk analysis chemistry metabolism MeSH
- Pupa physiology MeSH
- Manduca anatomy & histology physiology MeSH
- Microscopy, Electron, Scanning MeSH
- Feedback, Sensory physiology MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Plant defense metabolites are well known to be regulated developmentally. The optimal defense (OD) theory posits that a tssue's fitness values and probability of attack should determine defense metabolite allocations. Young leaves are expected to provide a larger fitness value to the plant, and therefore their defense allocations should be higher when compared with older leaves. The mechanisms that coordinate development with defense remain unknown and frequently confound tests of the OD theory predictions. Here we demonstrate that cytokinins (CKs) modulate ontogeny-dependent defenses in Nicotiana attenuata. We found that leaf CK levels highly correlate with inducible defense expressions with high levels in young and low levels in older leaves. We genetically manipulated the developmental patterns of two different CK classes by using senescence- and chemically inducible expression of CK biosynthesis genes. Genetically modifying the levels of different CKs in leaves was sufficient to alter ontogenic patterns of defense metabolites. We conclude that the developmental regulation of growth hormones that include CKs plays central roles in connecting development with defense and therefore in establishing optimal patterns of defense allocation in plants.
- MeSH
- Acetates metabolism pharmacology MeSH
- Herbivory physiology MeSH
- Time Factors MeSH
- Cyclopentanes metabolism pharmacology MeSH
- Cytokinins metabolism MeSH
- Plants, Genetically Modified MeSH
- Host-Parasite Interactions drug effects MeSH
- Plant Leaves genetics metabolism parasitology MeSH
- Manduca physiology MeSH
- Plant Diseases genetics parasitology MeSH
- Oxylipins metabolism pharmacology MeSH
- Gene Expression Regulation, Plant drug effects MeSH
- Plant Growth Regulators metabolism pharmacology MeSH
- Plant Proteins genetics metabolism MeSH
- Nicotiana genetics metabolism parasitology MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
For sexual communication, moths primarily use blends of fatty acid derivatives containing one or more double bonds in various positions and configurations, called sex pheromones (SPs). To study the molecular basis of novel SP component (SPC) acquisition, we used the tobacco hornworm (Manduca sexta), which uses a blend of mono-, di-, and uncommon triunsaturated fatty acid (3UFA) derivatives as SP. We identified pheromone-biosynthetic fatty acid desaturases (FADs) MsexD3, MsexD5, and MsexD6 abundantly expressed in the M. sexta female pheromone gland. Their functional characterization and in vivo application of FAD substrates indicated that MsexD3 and MsexD5 biosynthesize 3UFAs via E/Z14 desaturation from diunsaturated fatty acids produced by previously characterized Z11-desaturase/conjugase MsexD2. Site-directed mutagenesis of sequentially highly similar MsexD3 and MsexD2 demonstrated that swapping of a single amino acid in the fatty acyl substrate binding tunnel introduces E/Z14-desaturase specificity to mutated MsexD2. Reconstruction of FAD gene phylogeny indicates that MsexD3 was recruited for biosynthesis of 3UFA SPCs in M. sexta lineage via gene duplication and neofunctionalization, whereas MsexD5 representing an alternative 3UFA-producing FAD has been acquired via activation of a presumably inactive ancestral MsexD5. Our results demonstrate that a change as small as a single amino acid substitution in a FAD enzyme might result in the acquisition of new SP compounds.
- MeSH
- Fatty Acid Desaturases genetics metabolism MeSH
- Phylogeny MeSH
- Insect Proteins genetics metabolism MeSH
- Manduca genetics metabolism MeSH
- Evolution, Molecular * MeSH
- Molecular Sequence Data MeSH
- Fatty Acids, Unsaturated genetics metabolism MeSH
- Amino Acid Sequence MeSH
- Sex Attractants biosynthesis genetics MeSH
- Amino Acid Substitution * MeSH
- Animals MeSH
- Check Tag
- Female MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
The antioxidative potential of the Manduca sexta adipokinetic hormone (Manse-AKH) in the last instar larvae of Spodoptera littoralis (Noctuidae, Lepidoptera) was demonstrated after exposure to oxidative stress (OS) elicited by feeding on artificial diet containing tannic acid (TA). Determination of protein carbonyls (PCs) and reduced glutathione (GSH) levels, monitoring of activity of antioxidant enzymes catalase (CAT), superoxide dismutase (SOD) and glutathione-S-transferases (GSTs), as well as measuring of the mRNA expression of CAT and SOD were used as markers of the OS. Injection of the Manse-AKH (5 pmol per individual) reversed the OS status by mitigation of PCs formation and by stimulation of glutathione-S-transferases (GSTs) activity. The CAT and SOD mRNA expression was significantly suppressed after the Manse-AKH injection while activity of these enzymes was not affected. These results indicate that diminishing of OS after the AKH injection might be a result of activation of specific enzymatic pathway possibly at the post-translational level rather than a direct effect on regulation of antioxidant marker genes at the transcriptional level.
- MeSH
- Antioxidants metabolism MeSH
- Diet MeSH
- Glutathione metabolism MeSH
- Glutathione Transferase metabolism MeSH
- Insect Hormones pharmacology MeSH
- Insect Proteins genetics metabolism MeSH
- Catalase genetics metabolism MeSH
- Pyrrolidonecarboxylic Acid analogs & derivatives pharmacology MeSH
- Larva drug effects genetics metabolism MeSH
- Manduca chemistry MeSH
- Oligopeptides pharmacology MeSH
- Oxidative Stress drug effects MeSH
- Reverse Transcriptase Polymerase Chain Reaction MeSH
- Gene Expression Regulation, Enzymologic drug effects MeSH
- Spodoptera drug effects genetics metabolism MeSH
- Superoxide Dismutase genetics metabolism MeSH
- Tannins administration & dosage MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
