A multicomponent mandibular gland secretion in the ponerine ant Bothroponera soror (Emery)

The ponerine and Bothroponera soror has a complex mandibular gland secretion in which certain individual components release different behavioural responses. 2-undecanone releases alerting and orientation, 2-undecanol attraction and methyl-6-methylsalicylate, stinging. Field observations indicate that this multicomponent pheromone system enables small groups of ants to immobilize larger prey items.     

Caste and colony variations in the chemical composition of the cephalic secretions of the African weaver ant, Oecophylla longinoda

ABSTRACT. Considerable differences were found in the composition of the volatile cephalic chemical of the castes of Oecophylla longinoda. The mandibular glands of minor workers contain a series of primary alcohols, predominantly 1-hexanol, 1-octanol and 1-nonanol, together with nerol and geraniol. Hexanal, 2-butyl-2-octenal and 3-undecanone (components of the mandibular gland secretion of major workers, and which are important stimuli in alarm communication) are absent. Major workers are attracted and arrested by high concentrations of nerol, which is part of a possible mechanism for communication within the nest. The heads of males contain a pungent secretion, which may be used in defence; the major constituents are five aliphatic acids. The quantities of both main and trace constituents of the mandibular gland secretion of major workers were found to vary between colonies collected in different areas of West Africa.     

The orientation inducer pheromone of the fire ant Solenopsis invicta

Abstract Foraging ants recruit nestmate workers to food sources by a variety of mechanisms. We report that one behavioural subcategory of the recruitment pheromone complex of Solenopsis invicta Buren involves orientation induction. The orientation inducer pheromone exerts its effects by changing the physiological state of the recipient rather than by releasing a measurable behaviour. Some ant species use a physical 'waggle' behaviour to motivate (change physiological state) nestmate workers to follow their chemical trail. The orientation inducer pheromone can be interpreted as a chemical analogue of the physical 'waggle' inducing effects. This behaviour is not elicited by the recruitment pheromone components responsible for orientation and/or attraction. Each of these behavioural categories is mediated by a different blend of chemicals from the Dufour's gland. Activity-concentration thresholds indicate that the attraction and inducer part of the recruitment pheromone require about 250 times more worker equivalents for a response than the orientation pheromone. Therefore, the recruitment sub-categories are differentially activated by the amount of Dufour's gland material released.     

The X-ray structure of the type II secretion system complex formed by the N-terminal domain of EpsE and the cytoplasmic domain of EpsL of Vibrio cholerae

Gram-negative bacteria use type II secretion systems for the transport of virulence factors and hydrolytic enzymes through the outer membrane. These sophisticated multi-protein complexes reach from the pore in the outer membrane via the pseudopilins in the periplasm and a multi-protein inner-membrane sub-complex, to an ATPase in the cytoplasm. The human pathogen Vibrio cholerae uses such a secretion machinery, called the Eps-system, for the export of its major virulence factor cholera toxin into the intestinal tract of the human host. Here, we describe the 2.4 A structure of the hetero-tetrameric complex of the N-terminal domain of the ATPase EpsE and the cytoplasmic domain of the inner membrane protein EpsL, which constitute the major cytoplasmic components of the Eps-system. A stable fragment of EpsE in complex with the cytoplasmic domain of EpsL was identified via limited proteolysis and facilitated the crystallization of the complex. This first structure of a complex between two different proteins of the type II secretion system reveals that the N-terminal domain of EpsE and the cytoplasmic domain of EpsL form a hetero-tetramer, in which EpsL is the central dimer and EpsE binds on the periphery. The dimer of EpsL in this complex is very similar to the dimer seen in the crystal structure of the native cytoplasmic domain of EpsL, suggesting a possible physiological relevance despite a relatively small 675 A2 buried solvent accessible surface. The N-terminal domain of EpsE, which forms a compact domain with an alpha+beta-fold, places its helix alpha2 in a mostly hydrophobic cleft between domains II and III of EpsL burying 1700 A2 solvent accessible surface. This extensive interface involves several residues whose hydrophobic or charged nature is well conserved and is therefore likely to be of general importance in type II secretion systems.     

The volatile components of the mandibular gland secretion of workers of the ants Myrmica lobicornis and Myrmica sulcinodis

The mandibular glands of workers of M. lobicornis produce a mixture of 3-alkanones and 3-alkanols in the C₆–C₁₀ carbon chain length range, in addition to nanogram amounts of acetone, ethanal and 2-methylpropanal. Ethological studies have shown that the three major constituents, 3-octanol, 3-octanone and 3-decanol, are also the major pheromonally active components. When presented together they stimulate an alarm response in the workers similar to that induced by a worker's crushed head.In M. sulcinodis the mandibular gland secretion is composed of a mixture of the same ketones and alcohols, but in different proportions.     

Coordination of Raiding and Emigration in the Ponerine Army Ant Leptogenys distinguenda (Hymenoptera: Formicidae: Ponerinae): A Signal Analysis

Several glandular sources of trail pheromones have been discovered in army ants in general. Nevertheless, at present the understanding of the highly coordinated behavior of these ants is far from complete. The importance of trail pheromone communication for the coordination of raids and emigrations in the ponerine army ant Leptogenys distinguenda was examined, and its ecological function is discussed. The secretions of at least two glands organize the swarming activities of L. distinguenda. The pygidial gland is the source of an orientation pheromone holding the group of raiding workers together. The same pheromone guides emigrations to new nest sites. In addition, the poison sac contains two further components: one with a weak orientation effect and another which produces strong, but short-term attraction and excitement. The latter component is important in prey recruitment and characterizes raid trails. This highly volatile recruitment pheromone allows the extreme swarm dynamic characteristic of this species. Emigration trails lack the poison gland secretion. Due to their different chemical compositions, the ants are thus able to distinguish between raid and emigration trails. Nest emigration is not induced chemically, but mechanically, by the jerking movements of stimulating workers.     

The ontogenetic pattern of mandibular gland components in queenless worker bees (Apis mellifera capensis Esch.)

The quantity and composition of the six major mandibular gland components of young queenless workers of the Cape honeybee (Apis mellifera capensis) were determined. The total amount of the six components increased with age. The relative quantities in the mandibular gland secretion of queenless caged workers were found to change rapidly during the first 4 days after emergence and to become dominated by the queen substance, 9-keto-2(E)-decenoic acid. Also the relative amounts of 9-hydroxy-decenoic acid, a precursor of the queen substance, showed an increase of an order of magnitude within the first 4 days of imaginal life. The relative amounts of the aromatic compounds typical to the queen pheromone remained similar in this developmental time window. The increase of queenlike compounds is particularly strong between days two and three after emergence. These queen-like pheromones play a major role in the development of reproductive hierarchies among workers under queenless conditions. This may be an important factor in the socio-parasitic pathway of A. m. capensis.     

Ontogeny of queen attraction to workers in the antCataglyphis cursor (Hymenoptera: Formicidae)

Summary The behaviour ofCataglyphis cursor workers towards queens at 15 days, one month or two months after worker emergence was tested. Workers reared entirely with their own maternal queen were tested with this queen or with an unfamiliar alien queen. Workers transferred within 48 h of emerging to a new definitive nest with an alien queen were tested with this queen or with the original maternal queen. The degree of attraction to each of these queens and the workers' behavioural repertoire were measured and analysed. The results showed the following: 1) The attractiveness of queens and the workers' queen recognition behaviour were linked. 2) Although unfamiliar alien queens hardly attract workers, familiar alien queens were as attractive as maternal queens, and induced the same strongly marked and unique worker response, indicating that workers learn queen attractant cues in the days immediately after emergence. 3) Agonistic reactions were observed, but workers continued to be attracted to their maternal queen even after developing an attraction response to an alien queen with which they had been reared. These results agree with the proposal that queens produce two kinds of pheromones, those that attract workers and those that mediate recognition of queens by workers. These results show the ability of workers to discriminate between queens. Workers are attracted to any queen, but recognize as nestmates only maternal or alien queens with which they have been maintained. 4) The differential in worker attraction and recognition from 15 days to 2 months and its modifications by post-imaginal experience illustrate worker behavioural ontogeny, which is a basis of social discrimination.     

Temporal behavioral variation and division of labor among workers in the primitively eusocial wasp,Polistes jadwigae Dalla Torre

The behavior of workers on 2 nests of the Japanese paper wasp,Polistes jadwigae, was recorded on video tape. Young workers performed pulp collection more frequently than middle-aged and old workers, while foraging of flesh (prey) was done mainly by middle-aged workers. Of the 26 behavioral categories, 7 showed negative, 2 concave, and 1 convex relationship to the workers age. Using behavioral profiles, workers could be classified into 3 age groups: 1) young workers (younger than 10 days old, active intranidal workers), 2) middle-aged workers (11–25 days old, extranidal workers) and 3) old workers (older than 26 days old, ‘idlers’). Idlers engaged in foraging and larval feeding significantly less frequency than the young and middle-aged workers, but they performed alerting toward many alien objects. Task specialization among workers irrespective of age polyethism was also suggested.     

The mandibular gland secretion of the ant, Myrmica scabrinodis

ABSTRACT. The volatile secretion of the mandibular gland of the common elbowed red ant, Myrmica scabrinodis Nyl., is shown to consist of ethanal, ethanol, acetone, 3-hexanone, 3-hexanol, 3-heptanone, 3-heptanol, 3-octanone, 3-octanol, 6-methyl-3-octanone, 6-methyl-3-octanol, 3-nonanone, 3-nonanol, 3-decanone and 3-undecanone. The electroantennographic response to the major components was recorded and compared with some related compounds. Behavioural tests were carried out on the major constituents, showing that 3-octanol is an attractant for workers, that 3-octanone increases the effect of 3-octanol, and 3-nonanone augments the linear speed of the ants.     

The physicochemical transmission of two components of a multiple chemical signal in the African weaver ant, (Oecophylla longinoda)

The behavioural thresholds of the two principal components of the mandibular gland secretion in major workers of the weaver ant Oecophylla longinoda, hexanal and 1-hexanol, were found to be 1.99×10¹⁰ and 3.35×10¹¹ molecules cm^?3 respectively. The mandibular gland contains an average of 2.896×10¹⁵ molecules of hexanal, and 1.274×10¹⁶ molecules of 1-hexanol. From these measurements, molecular diffusion theory predicts behavioural active spaces for 1-hexanol (an attractant) which agree with those observed in response to the whole secretion, but there is no such agreemnet for haxanal (a releaser of behaviour with no directionial compnent). The effect of microturbulence on the transmission of releaser and chemotactic stimuli is discussed.     

Pseudomonas aeruginosa Minor Pilins Prime Type IVa Pilus Assembly and Promote Surface Display of the PilY1 Adhesin

Type IV pili (T4P) contain hundreds of major subunits, but minor subunits are also required for assembly and function. Here we show that Pseudomonas aeruginosa minor pilins prime pilus assembly and traffic the pilus-associated adhesin and anti-retraction protein, PilY1, to the cell surface. PilV, PilW, and PilX require PilY1 for inclusion in surface pili and vice versa, suggestive of complex formation. PilE requires PilVWXY1 for inclusion, suggesting that it binds a novel interface created by two or more components. FimU is incorporated independently of the others and is proposed to couple the putative minor pilin-PilY1 complex to the major subunit. The production of small amounts of T4P by a mutant lacking the minor pilin operon was traced to expression of minor pseudopilins from the P. aeruginosa type II secretion (T2S) system, showing that under retraction-deficient conditions, T2S minor subunits can prime T4P assembly. Deletion of all minor subunits abrogated pilus assembly. In a strain lacking the minor pseudopilins, PilVWXY1 and either FimU or PilE comprised the minimal set of components required for pilus assembly. Supporting functional conservation of T2S and T4P minor components, our 1.4 Å crystal structure of FimU revealed striking architectural similarity to its T2S ortholog GspH, despite minimal sequence identity. We propose that PilVWXY1 form a priming complex for assembly and that PilE and FimU together stably couple the complex to the major subunit. Trafficking of the anti-retraction factor PilY1 to the cell surface allows for production of pili of sufficient length to support adherence and motility.     

Contents of the poison apparatus of some species of Pheidole ants

Four Old World species of Pheidole ants contain different mixtures of farnesene-type hydrocarbons in their poison apparatus, and the mixture is different between the minor and major workers within a species. A bishomofarnesene (C₁₇H₂₈) provides approximately half of the secretion of the Dufour glands of minor workers of Pheidole pallidula. (Z,E)-α-Farnesene constituted 96% of the Dufour secretion of major workers of P. pallidula, but only 20% of that of minors. The Dufour glands of minor workers of Pheidole sinaitica contain a mixture of farnesene homologues with (Z,E)-α-farnesene and the bishomofarnesene also found in P. pallidula predominant. The mixture in major workers was similar but had, in addition, a small amount of (E)-β-farnesene. The Dufour glands of Pheidole teneriffana minors contain chiefly the same bishomofarnesene found in P. pallidula and P. sinaitica while major workers contain (Z,E)-α-farnesene. Pheidole megacephala minor workers contained small amounts of eight farnesenes, while major workers contained essentially no farnesenes. The poison glands of minor workers of P. pallidula contain 3-ethyl-2,5-dimethylpyrazine. No pyrazine compounds were found in the major workers of P. pallidula or the minor workers of P. sinaitica. The poison glands of the major workers of P. sinaitica contained larger amounts of tetra-substituted pyrazines. No pyrazines were found in the poison reservoirs of major or minor workers of P. teneriffana or P. megacephala.     

Structural and functional studies on the interaction of GspC and GspD in the type II secretion system

Type II secretion systems (T2SSs) are critical for secretion of many proteins from Gram-negative bacteria. In the T2SS, the outer membrane secretin GspD forms a multimeric pore for translocation of secreted proteins. GspD and the inner membrane protein GspC interact with each other via periplasmic domains. Three different crystal structures of the homology region domain of GspC (GspC(HR)) in complex with either two or three domains of the N-terminal region of GspD from enterotoxigenic Escherichia coli show that GspC(HR) adopts an all-β topology. N-terminal β-strands of GspC and the N0 domain of GspD are major components of the interface between these inner and outer membrane proteins from the T2SS. The biological relevance of the observed GspC-GspD interface is shown by analysis of variant proteins in two-hybrid studies and by the effect of mutations in homologous genes on extracellular secretion and subcellular distribution of GspC in Vibrio cholerae. Substitutions of interface residues of GspD have a dramatic effect on the focal distribution of GspC in V. cholerae. These studies indicate that the GspC(HR)-GspD(N0) interactions observed in the crystal structure are essential for T2SS function. Possible implications of our structures for the stoichiometry of the T2SS and exoprotein secretion are discussed.     

Trans-Golgi Network Localized ECHIDNA/Ypt Interacting Protein Complex Is Required for the Secretion of Cell Wall Polysaccharides in Arabidopsis

The secretion of cell wall polysaccharides through the trans-Golgi network (TGN) is required for plant cell elongation. However, the components mediating the post-Golgi secretion of pectin and hemicellulose, the two major cell wall polysaccharides, are largely unknown. We identified evolutionarily conserved YPT/RAB GTPase Interacting Protein 4a (YIP4a) and YIP4b (formerly YIP2), which form a TGN-localized complex with ECHIDNA (ECH) in Arabidopsis thaliana. The localization of YIP4 and ECH proteins at the TGN is interdependent and influences the localization of VHA-a1 and SYP61, which are key components of the TGN. YIP4a and YIP4b act redundantly, and the yip4a yip4b double mutants have a cell elongation defect. Genetic, biochemical, and cell biological analyses demonstrate that the ECH/YIP4 complex plays a key role in TGN-mediated secretion of pectin and hemicellulose to the cell wall in dark-grown hypocotyls and in secretory cells of the seed coat. In keeping with these observations, Fourier transform infrared microspectroscopy analysis revealed that the ech and yip4a yip4b mutants exhibit changes in their cell wall composition. Overall, our results reveal a TGN subdomain defined by ECH/YIP4 that is required for the secretion of pectin and hemicellulose and distinguishes the role of the TGN in secretion from its roles in endocytic and vacuolar trafficking.     

Chemical composition and rate of synthesis of the larval salivary secretion of the fly Rhynchosciara americana

The salivary secretion of Rhynchosciara americana was chemically analysed. The secretion shows a yellow colour, with a pH of 7·5 and protein as its major component (94·5 per cent of the secretion dry weight). Carbohydrates are minor components of the secretion which amount to 3·4 per cent of the secretion dry weight, of which 2·3 per cent are neutral carbohydrates and 1·1 per cent are galactosamine. The major amino acids present in the secretion proteins are aspartic acid, glycine, serine, and glutamic acid. The salivary secretion proteins can be separated into eleven protein fractions by urea-acrylamide gel electrophoresis from which nine fractions are PAS positive. The salivary pigment moves together with the protein fraction No. 8, which is quantitatively the most important one, and has spectral characteristics identical to a haemolymph pigment. The higher rate of gland protein labelling by ¹⁴C-phenylalanine determined in vivo and in vitro occurs around the middle of the spinning stage at the same time as the appearance of the large chromosomal puffs. The rôle of the salivary secretion in cocoon production is discussed.     

Formation of the full SNARE complex eliminates interactions of its individual protein components with the Kv2.1 channel

Previously, we have demonstrated physical and functional interactions of the voltage-gated potassium channel Kv2.1 with the plasma membrane protein components of the exocytotic SNARE complex, syntaxin 1A, and the t-SNARE, syntaxin 1A/SNAP-25, complex. Importantly, the physical interaction of Kv2.1 with syntaxin was shown to be involved in the facilitation of secretion from PC12 cells, which was independent of potassium currents. Recently, we showed that also VAMP2, the vesicular SNARE, interacts physically and functionally with Kv2.1. Here, we first set out to test the interaction of the full SNARE, syntaxin/SNAP-25/VAMP2, complex with the channel. Using the interaction of VAMP2 with Kv2.1 in Xenopus oocytes as a probe, we showed that coexpression of the t-SNARE complex with VAMP2 abolished the VAMP2 effect on channel inactivation and reduced the amount of VAMP2 that coprecipitated with Kv2.1. Further, in vitro pull down assays showed that the full SNARE complex failed to interact with Kv2.1 N- and C-termini in tandem, in contrast to the individual SNARE components. This suggests that the interactions of the SNARE components with Kv2.1 are abolished upon their recruitment into a full SNARE complex, which does not interact with the channel. Other important findings arising from the in vitro study are that the t-SNARE complex, in addition to syntaxin, interacts with a specific C-terminal channel domain, C1a, shown to mediate the facilitation of release by Kv2.1 and that the presence of Kv2.1 N-terminus has crucial contribution to these interactions. These findings provide important insights into the understanding of the complex molecular events involved in the novel phenomenon of secretion facilitation in neuroendocrine cells by Kv2.1.     

Type II secretion: from structure to function

Gram-negative bacteria use the type II secretion system to transport a large number of secreted proteins from the periplasmic space into the extracellular environment. Many of the secreted proteins are major virulence factors in plants and animals. The components of the type II secretion system are located in both the inner and outer membranes where they assemble into a multi-protein, cell-envelope spanning, complex. This review discusses recent progress, particularly newly published structures obtained by X-ray crystallography and electron microscopy that have increased our understanding of how the type II secretion apparatus functions and the role that individual proteins play in this complex system.     

Relative roles of resource stimulus and vegetation architecture on the paths of flies foraging for fruit

Many animals use their perceptual abilities to orient and locate resources in architecturally complex environments. However, it is not well known how the strength of a stimulus source affects the geometry of animal movement in architecturally complex environments. We mapped the 3D vegetation architecture of four apple trees of varying morphology and age and recorded the paths of apple maggot flies Rhagoletis pomonella foraging for artificial fruit. We compared the observed movement with the one obtained from a random walk model on a graph to estimate both 1) the attraction radius and strength of a fruit and 2) the relative roles of the architecture of vegetation and of the strength of attraction of a fruit on the movement of flies. The attraction radius is the maximal distance at which a stimulus source biases the movement of individuals and the attraction strength measures how strong this bias is. Plant architectural complexity is defined according to both foliage density and its 3D distribution within the canopy. A single fruit induces a bias in the path orientation of an insect that is at a large distance, relative to a tree volume, but it has no effect on the step length of moves. The plant complexity makes a minor contribution to defining the radius of the sphere of attraction, but a large contribution to the attraction strength. Conditional on visiting the location, the plant architecture plays a minor role compared to that of the presence of the fruit. Our findings show that the complexity of the environment can alter the use of sensory information, which has important implications for animal movements in complex environments. The importance of our results in animal dispersal and foraging is considered.