Attract and deter: a dual role for pyrrolizidine alkaloids in plant–insect interactions

Pyrrolizidine alkaloids (PAs) are the major defense compounds of plants in the Senecio genus. Here I will review the effects of PAs in Senecio on the preference and performance of specialist and generalist insect herbivores. Specialist herbivores have evolved adaptation to PAs in their host plant. They can use the alkaloids as cue to find their host plant and often they sequester PAs for their own defense against predators. Generalists, on the other hand, can be deterred by PAs. PAs can also affect survival of generalist herbivores. Usually generalist insects avoid feeding on young Senecio leaves, which contain a high concentration of alkaloids. Structurally related PAs can differ in their effects on insect herbivores, some are more toxic than others. The differences in effects of PAs on specialist and generalists could lead to opposing selection on PAs, which may maintain the genetic diversity in PA concentration and composition in Senecio species.     

Host-plant choice and larval growth in the cinnabar moth: do pyrrolizidine alkaloids play a role?

Witte et al. (1992) described two distinct chemotypes of Senecio jacobaea L. Asteraceae, a chemotype with jacobine as one of the major pyrrolizidine alkaloids (PAs) and a chemotype with erucifoline as one of the major PAs. We hypothesized that the presence of erucifoline might be the factor responsible for the lack of success of the cinnabar moth on Senecio erucifolius L. Asteraceae and the S. jacobaea erucifoline chemotype. We performed a survey of the distribution of the two chemotypes in the Netherlands and compared this with the distribution map of Tyria jacobaeae L. Lepidoptera, Arctiidae. The distribution of the two chemotypes in the Netherlands is poorly correlated with the distribution of the cinnabar moth. The jacobine chemotype occurs along the coast and the erucifoline chemotype predominantly inward.An oviposition experiment showed that the cinnabar moth did not discriminate between the two chemotypes of S. jacobaea and S. erucifolius. Larval performance did not differ between the two chemotypes and species. Although the distribution of S. jacobaea jacobine chemotype is loosely associated with the abundance of the cinnabar moth the oviposition and growth experiments indicate that other factors than the presence of erucifoline play a role in this association.The absence of recordings of S. erucifolius as a foodplant for the cinnabar moth might be explained by the phenology of the foodplant. Ovipositing females of the univoltine cinnabar moth prefer flowering plants for oviposition. S. erucifolius starts flowering about 1–2 month later than S. jacobaea just after the peak density of moths.     

A free lunch? No cost for acquiring defensive plant pyrrolizidine alkaloids in a specialist arctiid moth (Utetheisa ornatrix)

Many herbivorous insects sequester defensive chemicals from their host plants. We tested sequestration fitness costs in the specialist moth Utetheisa ornatrix (Lepidoptera: Arctiidae). We added pyrrolizidine alkaloids (PAs) to an artificial diet at different concentrations. Of all the larval and adult fitness components measured, only development time was negatively affected by PA concentration. These results were repeated under stressful laboratory conditions. On the other hand, the amount of PAs sequestered greatly increased with the diet PA concentration. Absence of a detectable negative effect does not necessarily imply a lack of costs if all individuals express the biochemical machinery of detoxification and sequestration constitutively. Therefore, we used qPCR to show that expression of the gene used to detoxify PAs, pyrrolizidine‐alkaloid‐N‐oxygenase (pno), increased 41‐fold in our highest PA treatment. Nevertheless, fitness components were affected only slightly or not at all, suggesting that sequestration in this species does not incur a strong cost. The apparent lack of costs has important implications for our understanding of the evolution of ecological interactions; for example, it implies that selection by specialist herbivores may decrease the levels of certain chemical defences in plant populations.     

Response to novel food in infant chimpanzees: Do infants refer to mothers before ingesting food on their own?

We investigated infant response toward novel food in captive chimpanzees under the condition in which they can explore such items freely together with their mother. Infants first approached novel foods rather than familiar ones when presented simultaneously. However, they did not ingest novel food immediately, but always sniff-licked it first. Infants tended to pay attention to their mothers before mouthing or ingesting novel foods themselves, but never did so with familiar ones. In response to the infant's activity, mother chimpanzees were tolerant rather than actively interfering. Those results imply that chimpanzee infants respond to novel foods in a neophobic way and refer to their mother for some kind of cue before attempting to ingest them.     

Dietary diversification and variations in the number of labrum sensilla in grasshoppers: Which came first?

The diversity of the diet of grasshoppers (Acrididae, Orthoptera) is related to multiple factors, including the chemoreceptors on the antennae, palps and on the epipharyngeal face of the labrum. In the present study, we sought to understand the nature of the diet of 12 Moroccan acridian species and to try to relate various aspects of their diet to the number of labrum sensilla. If the effect of the labrum size on the number of sensilla is removed, four groups of species are recorded: (i) polyphagous species with a broad diet and numerous sensilla; (ii) polyphagous species with a graminivorous diet and numerous sensilla; (iii) oligophagous species feeding exclusively on Poaceae and with a medium number of sensilla; and (iv) strictly monophagous species feeding on a single plant species and with the smallest number of sensilla. These observations show the close relationship between the diet and the number of labrum sensilla. However, Sphingonotus rubescens, a polyphagous species, is an exception to this trend as it harbours a medium number of sensilla. We propose that the modification in the number of labrum sensilla is a result of a progressive adaptation to a different diet and does not represent its cause.     

Can edible grasshoppers and silkworm pupae be tasted by humans when prevented to see and smell these insects?

Out of 26 students (11 male, 15 female) that were blindfolded and held their noses, 14 correctly identified the taste of insects when given pieces of cheese, dried fish, beondaegi (commercially available Korean Bombyx mori silkworm pupae), inago (commercially available Japanese Oxya yezoensis grasshoppers) and white bread to taste. Eight identified one of the food insects and four failed to detect any. Of 11 students given a choice between beondaegi, inago and hachinoko (larval wasps of Vespula flaviceps) most students preferred the inago grasshoppers, three ranked the commercially available hachinoko first and one gave the top position to the beondaegi silkworm pupae. It is concluded that insects, per se, are not terribly easy to identify by taste alone. Given the well documented aversion of especially people of western cultural backgrounds to insects in food, our results suggest that insects processed into flour or pastes have a greater chance to be accepted by the consumer (as they cannot easily be identified by taste alone) than food that displays insect images on its packing.

Why do nocturnal grasshoppers and katydids “salute” to flash photography?

Nocturnal animals can be sensitive to powerful light from the environment. Anthropogenically induced perturbation to natural light regimes, including ecological light pollution and flash photography, can have wide‐reaching implications on the ecology and behavior. Ecological ramifications of strong lights were traditionally focused on vertebrates although there is now more focus on invertebrates. Nonetheless, there are still unanswered questions on visual ecology and evolution, particularly on individual‐level effects and of tropical species. Specifically, how invertebrate individuals react to strong light is generally undocumented. Based on opportunistic surveys around Southeast Asia, orthopterans, spotted using concentrated torchlight and exposed to sudden strong light intensity during flash macrophotography, were observed to screen themselves by positioning their foreleg over the dorsum of the compound eye. This resembled the orthopteran “saluting” to the camera. These observations provided empirical evidence of how high intensity light can unsettle orthopterans and other insects and further ecological and evolutionary hypotheses and questions can be raised to understand the effect of light pollution.     

Naturally-occurring tetrahydro-β-carboline alkaloids derived from tryptophan are oxidized to bioactive β-carboline alkaloids by heme peroxidases

β-Carbolines are indole alkaloids that occur in plants, foods, and endogenously in mammals and humans, and which exhibit potent biological, psychopharmacological and toxicological activities. They form from naturally-occurring tetrahydro-β-carboline alkaloids arising from tryptophan by still unknown way and mechanism. Results in this research show that heme peroxidases catalyzed the oxidation of tetrahydro-β-carbolines (i.e. 1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid and 1-methyl-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid) into aromatic β-carbolines (i.e. norharman and harman, respectively). This oxidation followed a typical catalytic cycle of peroxidases through redox intermediates I, II, and ferric enzyme. Both, plant peroxidases (horseradish peroxidase, HRP) and mammalian peroxidases (myeloperoxidase, MPO and lactoperoxidase, LPO) catalyzed the oxidation in an efficient manner as determined by kinetic parameters (V_MAX and K_M). Oxidation of tetrahydro-β-carbolines was inhibited by peroxidase inhibitors such as sodium azide, ascorbic acid, hydroxylamine and excess of H₂O₂. The formation of aromatic β-carbolines by heme peroxidases can help to explain the presence and activity of these compounds in biological systems.     

Do broiler chicks have a cognitive representation of food quality?. Appetitive, behavioural and ingestive responses to a change in diet quality

It has been observed that when a new diet formulation, or a new batch of the same diet formulation, is presented to poultry, there is a transitory suppression of feeding. It appears that the birds do not recognise the food as being edible, or classify it as being 'unknown'. In order to understand more about food recognition and rejection, the aim of this experiment was to determine whether cognitive processes are involved. Sixteen groups of four broiler chicks were used, and were fed a low quality diet in their home pens. The groups of chicks were trained to run a winding maze to gain access to a high quality diet in a test trough for 15min per day. When training was completed, the feed in the test trough for eight of the groups was changed to that which they received in the home pen, while the other eight groups received no change as a control. Time to traverse the runway did not show an immediate decrease on the day after the change (P>0.05) as would be expected if the birds used a cognitive comparison to determine speed of approach to the test trough. However, the experimental groups were significantly slower compared to the control groups after 4 days (P<0.05). The behaviour observed on the day of the change was indicative of frustration with more scratching and hurried movements shown (P<0.05), and less pecking at feed (P<0.01). Food consumption was lower for experimental groups compared to control groups on all days from the day of change onward (P<0.001). It was concluded that although there was no definitive evidence for the presence of a cognitive representation of food, this may have been due in part to the testing of groups of birds rather than individuals, and the way in which food quality is perceived. The occurrence of behaviours indicative of frustration suggest that a cognitive expectation may have been present.     

Comparative proteomic analysis of Methanothermobacter themautotrophicus ΔH in pure culture and in co-culture with a butyrate-oxidizing bacterium

To understand the physiological basis of methanogenic archaea living on interspecies H(2) transfer, the protein expression of a hydrogenotrophic methanogen, Methanothermobacter thermautotrophicus strain ΔH, was investigated in both pure culture and syntrophic coculture with an anaerobic butyrate oxidizer Syntrophothermus lipocalidus strain TGB-C1 as an H(2) supplier. Comparative proteomic analysis showed that global protein expression of methanogen cells in the model coculture was substantially different from that of pure cultured cells. In brief, in syntrophic coculture, although methanogenesis-driven energy generation appeared to be maintained by shifting the pathway to the alternative methyl coenzyme M reductase isozyme I and cofactor F(420)-dependent process, the machinery proteins involved in carbon fixation, amino acid synthesis, and RNA/DNA metabolisms tended to be down-regulated, indicating restrained cell growth rather than vigorous proliferation. In addition, our proteome analysis revealed that α subunits of proteasome were differentially acetylated between the two culture conditions. Since the relevant modification has been suspected to regulate proteolytic activity of the proteasome, the global protein turnover rate could be controlled under syntrophic growth conditions. To our knowledge, the present study is the first report on N-acetylation of proteasome subunits in methanogenic archaea. These results clearly indicated that physiological adaptation of hydrogenotrophic methanogens to syntrophic growth is more complicated than that of hitherto proposed.     

How to address CPP and AMP translocation? Methods to detect and quantify peptide internalization in vitro and in vivo (Review)

Membrane translocation is a crucial issue when addressing the activity of both cell-penetrating and antimicrobial peptides. Translocation is responsible for the therapeutic potential of cell-penetrating peptides as drug carriers and can dictate the killing mechanisms, selectivity and efficiency of antimicrobial peptides. It is essential to evaluate if the internalization of cell-penetrating peptides is mediated by endocytosis and if it is able to internalize attached cargoes. The mode of action of an antimicrobial peptide cannot be fully understood if it is not known whether the peptide acts exclusively at the membrane level or also at the cytoplasm. Therefore, experimental methods to evaluate and quantify translocation processes are of first importance. In this work, over 20 methods described in the literature for the assessment of peptide translocation in vivo and in vitro, with and without attached macromolecular cargoes, are discussed and their applicability, advantages and disadvantages reviewed. In addition, a classification of these methods is proposed, based on common approaches to detect translocation.     

Induction by alkaloids and phenobarbital of Family 4 Cytochrome P450s in Drosophila : evidence for involvement in host plant utilization

In vertebrates, cytochrome P450s of the CYP2 and CYP3 families play a dominant role in drug metabolism, while in insects members of the CYP6 and CYP28 families have been implicated in metabolism of insecticides and toxic natural plant compounds. A degenerate 3^′ RACE strategy resulted in the identification of fifteen novel P450s from an alkaloid-resistant species of Drosophila. The strong (17.4-fold) and highly specific induction of a single gene (CYP4D10) by the toxic isoquinoline alkaloids of a commonly utilized host-plant (saguaro cactus) provides the first indication that members of the CYP4 family in insects may play an important role in the maintenance of specific insect-host plant relationships. Strong barbiturate inducibility of CYP4D10 and two other D. mettleri P450 sequences of the CYP4 family was also observed, suggesting a pattern of xenobiotic responsiveness more similar to those of several vertebrate drug-metabolizing enzymes than to putative vertebrate CYP4 homologs.     

Left and right in the amphibian world: which way to develop and where to turn?

The last decade has seen a dramatic increase in studies on the development, function and evolution of asymmetries in vertebrates, including amphibians. Here we discuss current knowledge of behavioral and anatomical asymmetries in amphibians. Behavioral laterality in the response of both adult and larval anurans to presumed predators and competitors is strong and may be related, respectively, to laterality in the telencephalon of adults and the Mauthner neurons of tadpoles. These behavior lateralities, however, do not seem to correlate with visceral asymmetries in the same animals. We briefly compare what is known about the evolution and development of asymmetry in the structure and function of amphibians with what is known about asymmetries in other chordate and non-chordate groups. Available data suggest that the majority of asymmetries in amphibians fall into two independent groups: (1) related to situs viscerum and (2) of a neurobehavioral nature. We find little evidence linking these two groups, which implies different developmental regulatory pathways and independent evolutionary histories for visceral and telencephalic lateralizations. Studies of animals other than standard model species are essential to test hypotheses about the evolution of laterality in amphibians and other chordates.     

Structure in parasite component communities in wild rodents: predictability, stability, associations and interactions .... or pure randomness?

Experimental data establish that interactions exist between species of intestinal helminths during concurrent infections in rodents, the strongest effects being mediated through the host's immune responses. Detecting immune-mediated relationships in wild rodent populations has been fraught with problems and published data do not support a major role for interactions in structuring helminth communities. Helminths in wild rodents show predictable patterns of seasonal, host age-dependent and spatial variation in species richness and in abundance of core species. When these are controlled for, patterns of co-infection compatible with synergistic interactions can be demonstrated. At least one of these, the positive relationship between Heligmosomoides polygyrus and species richness of other helminths has been demonstrated in three totally independent data-sets. Collectively, they explain only a small percentage of the variance/deviance in abundance data and at this level are unlikely to play a major role in structuring helminth communities, although they may be important in the more heavily infected wood mice. Current worm burdens underestimate the possibility that earlier interactions through the immune system have taken place, and therefore interactions may have a greater role to play than is immediately evident from current worm burdens. Longitudinal studies are proposed to resolve this issue.     

Venom alkaloids in Monomorium “rothsteini” Forel repel other ants: is this the secret to success by Monomorium in Australian ant communities?

Summary Species of the cosmopolitan ant genus Monomorium are small, slow-moving and non-aggressive ants that are extremely successful members of diverse Australian ant communities. Unlike other abundant taxa, they have no obvious specializations enabling them to co-exist with the highly aggressive species of Iridomyrmex that dominate these communities. Here we report results which suggest that Monomorium species owe their success to the topical application of venom alkaloids which repel other ants. The venom alkaloids (trans-2-ethyl-5-undecylpyrrolidine and trans-2-ethyl-5-tridecylpyrrolidine) of Monomorium rothsteini were identified and synthesized, and the repellency to other ants of the synthetic alkaloids were tested using bioassays involving the attraction to honey baits of three native species of Iridomyrmex, three tropical tramp species, and M. rothsteini itself. Repellency to all other ant species was total or nearly so, but only partial to M. rothsteini. Defensive alkaloids produced from a variety of glands are found in other ant genera, and may be a potent yet poorly appreciated force in interference competition between ant species and thereby the structure of ant communities.     

Resistance to glufosinate is proportional to phosphinothricin acetyltransferase expression and activity in LibertyLink® and WideStrike® cotton

Planta - Insertion of the gene encoding phosphinothricin acetyltransferase (PAT) has resulted in cotton plants resistant to the herbicide glufosinate. However, the lower expression and commensurate...     

Actinomycetes biosynthetic potential: how to bridge in silico and in vivo?

Actinomycetes genome sequencing and bioinformatic analyses revealed a large number of “cryptic” gene clusters coding for secondary metabolism. These gene clusters have the potential to increase the chemical diversity of natural products. Indeed, reexamination of well-characterized actinomycetes strains revealed a variety of hidden treasures. Growing information about this metabolic diversity has promoted further development of strategies to discover novel biologically active compounds produced by actinomycetes. This new task for actinomycetes genetics requires the development and use of new approaches and tools. Application of synthetic biology approaches led to the development of a set of strategies and tools to satisfy these new requirements. In this review, we discuss strategies and methods to discover small molecules produced by these fascinating bacteria and also discuss a variety of genetic instruments and regulatory elements used to activate secondary metabolism cryptic genes for the overproduction of these metabolites.