Die mögliche Rolle der antennalen Cuticularporen beim Sexualverhalten von Cyaneolytta sp. (Coleoptera: Meloidae)

Cantharidin, which is mainly found in blister beetles (Coleoptera: Meloidae), is one of the most intensively studied natural products of insect (Dettner, 1997; McCormick & Carrel, 1987). The involvement of cantharidin in courtship behaviour has been already confirmed for certain canthariphilous insects (Eisner & al. 1996a,b; Frenzel & Dettner 1994; Frenzel & al. 1992; Schütz & Dettner, 1992; Hemp & al. 1999). The function and intrinsinc role of cantharidin in the courtship behaviour of Meloids has been never fully established. McCormick & Carrel (1987) only suggested that cantharidin might be used by female meloids when selecting a mate at close range. Pinto (1974, 1975) was, in fact, the first to consider male cuticular pores as being involved in the courtship behaviour of species from the genus Linsleya and Tegrodera (Meloidae). Based on morphology and chemical analyses of Cyaneolytta sp. (Coleoptera: Meloidae), we have hereby provided some further evidences that cantharidin may act as an infochemical in courtship behaviour of meloid beetles.Ölkäfer (Col: Meloidae) gehören zu den Insekten mit medizinischer Bedeutung. Cantharidin, das im gesamten Körper (v.a. in den Sexualorganen beider Geschlechter) der Käfer zu finden ist, verursacht Blasen auf der Haut. Die mögliche Rolle des Cantharidins im Sexualverhalten der Ölkäfer ist von besonderem wissenschaftlichem Interesse. Cyaneolytta sp. wurde in Karen, Kenia, gesammelt. Nach der Sektion wurden die Insektenkompartimente hydrolysiert und mittels quantitativer GC-MS chemisch analysiert. Um Poren der Kutikula und andere äußere Merkmale zu untersuchen, wurde ein Rasterelektronenmikroskop verwendet. Für Dünnschnitte der inneren Gewebe wurden Mikrotomschnitte angefertigt. Statistische Analysen wurden mit dem Softwarepaket Statistica durchgeführt. In den Antennen von Cyaneolytta sp. Péringuey, 1909 finden sich extrem hohe Cantharidinmengen. Die Daten zeigen eine deutliche Korrelation zwischen der Dichte der Kutikularporen und dem Cantharidingehalt der Antennenglieder Scapus und Pedicellus der Cyaneolytta-Männchen. Es existieren zahlreiche kanalartige Strukturen, die sich von der Hämolymphe der Antennen zur Oberfläche erstrecken, wo sich die Kutikularporen befinden. Betrachtet man den Cantharidingehalt der Antennensegmente, so enthalten die Glieder der Männchen viel größere Mengen als die der Weibchen. Auch besitzen die Kutikularporen der Weibchen eine deutlich geringere Dichte auf den Antennensegmenten. Die kanalartigen Strukturen auf den ersten beiden Antennensegmenten der Weibchen könnten uni- oder multizelluläre Tubuli sein, die das in der Hämolymphe zirkulierende Cantharidin an die Oberfläche bringen, aber die Poren auf den Antennen der Weibchen müssen eine andere Funktion haben. Während des Balzverhaltens berühren sich beide Geschlechter mit den Antennen, wobei die cantharidinhaltigen Poren in direkten Kontakt mit den weiblichen Antennen gelangen. Es wird vermutet, dass Cantharidin an die Oberfläche der Antennen der Männchen abgegeben wird. Demnach könnte der porenhaltige Bereich der männlichen Antennen eine Struktur sein, die Cantharidin abgibt, während der porenhaltige Bereich der weiblichen Antennen ein Rezeptorfeld darstellen könnte, dessen Chemorezeptoren einen bevorzugten Geschlechtspartner erkennen. Damit wurden weitere Hinweise für die Hypothese gesammelt, dass Cantharidin eine Rolle bei der sexuellen Selektion im Nahbereich spielt

The Microbiome of Spodoptera littoralis: Development, Control and Adaptation to the Insect Host

The symbiotic microbial consortium in the gut of Spodoptera littoralis shows dramatic, but reproducible changes in line with the development of the insect from the egg via six larval instars to the pupa. Since the food is kept constant during development, factors from the insect host and certain microbial symbionts are assumed to control the composition of the microbiome. A GFP-tagged Enterococcus mundtii, one of the major players of the consortium, easily integrates into the microbiome and can be monitored in all gut segments at all developmental stages. The reporter organism can be recovered from the gut using a preparative flow cytometry allowing subsequent RNA extraction for transcriptomic analyses. The transcriptomic profile from the fluorescent Enterococcus cells provides information on the adaptation of the reporter organism to the local gut conditions. The concept of using a fluorescent reporter organism that can be recovered at any time from any area of the intestinal tract will allow a holistic analysis of adaptation strategies used by the microbes to adapt to the insect gut. In combination with the analysis of transcript patterns from the gut membranes, a first insight into the molecular interaction between the insect host and the microbiome can be expected

The Role of Jasmonates in Floral Nectar Secretion

Plants produce nectar in their flowers as a reward for their pollinators and most of our crops depend on insect pollination, but little is known on the physiological control of nectar secretion. Jasmonates are well-known for their effects on senescence, the development and opening of flowers and on plant defences such as extrafloral nectar. Their role in floral nectar secretion has, however, not been explored so far. We investigated whether jasmonates have an influence on floral nectar secretion in oil-seed rape, Brassica napus. The floral tissues of this plant produced jasmonic acid (JA) endogenously, and JA concentrations peaked shortly before nectar secretion was highest. Exogenous application of JA to flowers induced nectar secretion, which was suppressed by treatment with phenidone, an inhibitor of JA synthesis. This effect could be reversed by additional application of JA. Jasmonoyl-isoleucine and its structural mimic coronalon also increased nectar secretion. Herbivory or addition of JA to the leaves did not have an effect on floral nectar secretion, demonstrating a functional separation of systemic defence signalling from reproductive nectar secretion. Jasmonates, which have been intensively studied in the context of herbivore defences and flower development, have a profound effect on floral nectar secretion and, thus, pollination efficiency in B. napus. Our results link floral nectar secretion to jasmonate signalling and thereby integrate the floral nectar secretion into the complex network of oxylipid-mediated developmental processes of plants

Solar off-limb line widths: Alfven waves, ion-cyclotron waves, and preferential heating

Alfven waves and ion-cyclotron absorption of high-frequency waves are frequently brought into models devoted to coronal heating and fast solar-wind acceleration. Signatures of ion-cyclotron resonance have already been observed in situ in the solar wind (HELIOS spacecrafts) and, recently, in the upper corona (UVCS/SOHO remote-sensing results). We propose a method to constrain both the Alfven wave amplitude and the preferential heating induced by ion-cyclotron resonance, above a partially developed polar coronal hole observed with the SUMER/SOHO spectrometer. The instrumental stray light contribution is first substracted from the spectra. By supposing that the non-thermal velocity is related to the Alfven wave amplitude, it is constrained through a density diagnostic and the gradient of the width of the Mg X 625 A line. The temperatures of several coronal ions, as functions of the distance above the limb, are then determined by substracting the non-thermal component to the observed line widths. The effect of stray light explains the apparent decrease with height in the width of several spectral lines, this decrease usually starting about 0.1-0.2 Rs above the limb. This result rules out any direct evidence of damping of the Alfven waves, often suggested by other authors. We also find that the ions with the smallest charge-to-mass ratios are the hottest ones at a fixed altitude and that they are subject to a stronger heating, as compared to the others, between 57" and 102" above the limb. This constitutes a serious clue to ion-cyclotron preferential heating.Comment: 15 pages, 12 figures, 3 table

The oxylipin chemistry of attraction and defense in brown algae and diatoms

Max Planck Institute for Chemical Ecology, Jena, Germany. This review covers the research on brown algal pheromones from the first structural characterisation of an active principle in 1971 to the recent detailed insight into their biosynthesis. Development of analytical methods and bioassays that lead to the identification of a structural variety of different fatty acid-derived pheromones are reported. Special emphasis is focused on the inactivation of initially released pheromones through pericyclic reactions. The impact of pheromone-research on the defensive chemistry of brown algae and diatoms is discussed. 121 references are cited

Thioglycosides as inhibitors of hSGLT1 and hSGLT2: Potential therapeutic agents for the control of hyperglycemia in diabetes

The treatment of diabetes has been mainly focused on maintaining normal blood glucose concentrations. Insulin and hypoglycemic agents have been used as standard therapeutic strategies. However, these are characterized by limited efficacy and adverse side effects, making the development of new therapeutic alternatives mandatory. Inhibition of glucose reabsorption in the kidney, mediated by SGLT1 or SGLT2, represents a promising therapeutic approach. Therefore, the aim of the present study was to evaluate the effect of thioglycosides on human SGLT1 and SGLT2. For this purpose, stably transfected Chinese hamster ovary (CHO) cells expressing human SGLT1 and SGLT2 were used. The inhibitory effect of thioglycosides was assessed in transport studies and membrane potential measurements, using α-methyl-glucoside uptake and fluorescence resonance energy transfer, respectively. We found that some thioglycosides inhibited hSGLT more strongly than phlorizin. Specifically, thioglycoside I (phenyl-1'-thio-β-D-glucopyranoside) inhibited hSGLT2 stronger than hSGLT1 and to a larger extent than phlorizin. Thioglycoside VII (2-hydroxymethyl-phenyl-1'-thio-β-D-galacto-pyranoside) had a pronounced inhibitory effect on hSGLT1 but not on hSGLT2. Kinetic studies confirmed the inhibitory effect of these thioglycosides on hSGLT1 or hSGLT2, demonstrating competitive inhibition as the mechanism of action. Therefore, these thioglycosides represent promising therapeutic agents for the control of hyperglycemia in patients with diabetes

Chemical composition and antimicrobial activity of essential oil from Pyrethrum pulchrum Ledeb.

The chemical composition and antimicrobial activity of the essential oil from the aerial parts of Pyrethrum pulchrum Ledeb. were investigated. Dried plant material was hydro-distillated yielding 0.1% of essential oil. The oil was analyzed by GC-MS techniques. Fifty-five compounds were identified representing 99.7% of the total oil composition. Camphor was the predominant compound (33.9%) followed by linalool (21.1%) and α-pinene (9.0%). The antimicrobial activity of the oil was determined using the disk diffusion method against Gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus and Enterococcus faecalis), Gram-negative bacteria (Pseudomonas aeruginosa and Escherichia coli), Mycobacterium vaccae and fungi (Candida albicans, Sporidiobolus salmonicolor and Penicillum notatum). The essential oil of P. pulchrum displays an intermediate activity against selected bacteria

The Yeast Three-Hybrid System as an Experimental Platform to Identify Proteins Interacting with Small Signaling Molecules in Plant Cells: Potential and Limitations

Chemical genetics is a powerful scientific strategy that utilizes small bioactive molecules as experimental tools to unravel biological processes. Bioactive compounds occurring in nature represent an enormous diversity of structures that can be used to dissect functions of biological systems. Once the bioactivity of a natural or synthetic compound has been critically evaluated the challenge remains to identify its molecular target and mode of action, which usually is a time-consuming and labor-intensive process. To facilitate this task, we decided to implement the yeast three-hybrid (Y3H) technology as a general experimental platform to scan the whole Arabidopsis proteome for targets of small signaling molecules. The Y3H technology is based on the yeast two-hybrid system and allows direct cloning of proteins that interact in vivo with a synthetic hybrid ligand, which comprises the biologically active molecule of interest covalently linked to methotrexate (Mtx). In yeast nucleus the hybrid ligand connects two fusion proteins: the Mtx part binding to dihydrofolate reductase fused to a DNA-binding domain (encoded in the yeast strain), and the bioactive molecule part binding to its potential protein target fused to a DNA-activating domain (encoded on a cDNA expression vector). During cDNA library screening, the formation of this ternary, transcriptional activator complex leads to reporter gene activation in yeast cells, and thereby allows selection of the putative targets of small bioactive molecules of interest. Here we present the strategy and experimental details for construction and application of a Y3H platform, including chemical synthesis of different hybrid ligands, construction of suitable cDNA libraries, the choice of yeast strains, and appropriate screening conditions. Based on the results obtained and the current literature we discuss the perspectives and limitations of the Y3H approach for identifying targets of small bioactive molecules

A cuckoo in wolves' clothing? Chemical mimicry in a specialized cuckoo wasp of the European beewolf (Hymenoptera, Chrysididae and Crabronidae)

<p>Abstract</p> <p>Background</p> <p>Host-parasite interactions are among the most important biotic relationships. Host species should evolve mechanisms to detect their enemies and employ appropriate counterstrategies. Parasites, in turn, should evolve mechanisms to evade detection and thus maximize their success. Females of the European beewolf (<it>Philanthus triangulum</it>, Hymenoptera, Crabronidae) hunt exclusively honeybee workers as food for their progeny. The brood cells containing the paralyzed bees are severely threatened by a highly specialized cuckoo wasp (<it>Hedychrum rutilans</it>, Hymenoptera, Chrysididae). Female cuckoo wasps enter beewolf nests to oviposit on paralyzed bees that are temporarily couched in the nest burrow. The cuckoo wasp larva kills the beewolf larva and feeds on it and the bees. Here, we investigated whether <it>H. rutilans </it>evades detection by its host. Since chemical senses are most important in the dark nest, we hypothesized that the cuckoo wasp might employ chemical camouflage.</p> <p>Results</p> <p>Field observations suggest that cuckoo wasps are attacked by beewolves in front of their nest, most probably after being recognized visually. In contrast, beewolves seem not to detect signs of the presence of these parasitoids neither when these had visited the nest nor when directly encountered in the dark nest burrow.</p> <p>In a recognition bioassay in observation cages, beewolf females responded significantly less frequently to filter paper discs treated with a cuticular extract from <it>H. rutilans </it>females, than to filter paper discs treated with an extract from another cuckoo wasp species (<it>Chrysis viridula</it>). The behavior to paper discs treated with a cuticular extract from <it>H. rutilans </it>females did not differ significantly from the behavior towards filter paper discs treated with the solvent only.</p> <p>We hypothesized that cuckoo wasps either mimic the chemistry of their beewolf host or their host's prey. We tested this hypothesis using GC-MS analyses of the cuticles of male and female beewolves, cuckoo wasps, and honeybee workers. Cuticle extracts of <it>Hedychrum nobile </it>(Hymenoptera: Chrysididae) and <it>Cerceris arenaria </it>(Hymenoptera: Crabronidae) were used as outgroups. There was little congruence with regard to cuticular compounds between <it>H. rutilans </it>females and honeybees as well as females of <it>C. arenaria </it>and <it>H. nobile</it>. However, there was a considerable similarity between beewolf females and <it>H. rutilans </it>females. Beewolf females show a striking dimorphism regarding their cuticular hydrocarbons with one morph having (<it>Z</it>)-9-C25:1 and the other morph having (<it>Z</it>)-9-C27:1 as the major component. <it>H. rutilans</it> females were more similar to the morph having (Z)-9-C27:1 as the main component.</p> <p>Conclusion</p> <p>We conclude that <it>H. rutilans </it>females closely mimic the composition of cuticular compounds of their host species <it>P. triangulum</it>. The occurrence of isomeric forms of certain compounds on the cuticles of the cuckoo wasps but their absence on beewolf females suggests that cuckoo wasps synthesize the cuticular compounds rather than sequester them from their host. Thus, the behavioral data and the chemical analysis provide evidence that a specialized cuckoo wasp exhibits chemical mimicry of the odor of its host. This probably allows the cuckoo wasp to enter the nest with a reduced risk of being detected by olfaction and without leaving traitorous chemical traces.</p