Caterpillars and fungal pathogens: two co-occurring parasites of an ant-plant mutualism

In mutualisms, each interacting species obtains resources from its partner that it would obtain less efficiently if alone, and so derives a net fitness benefit. In exchange for shelter (domatia) and food, mutualistic plant-ants protect their host myrmecophytes from herbivores, encroaching vines and fungal pathogens. Although selective filters enable myrmecophytes to host those ant species most favorable to their fitness, some insects can by-pass these filters, exploiting the rewards supplied whilst providing nothing in return. This is the case in French Guiana for Cecropia obtusa (Cecropiaceae) as Pseudocabima guianalis caterpillars (Lepidoptera, Pyralidae) can colonize saplings before the installation of their mutualistic Azteca ants. The caterpillars shelter in the domatia and feed on food bodies (FBs) whose production increases as a result. They delay colonization by ants by weaving a silk shield above the youngest trichilium, where the FBs are produced, blocking access to them. This probable temporal priority effect also allows female moths to lay new eggs on trees that already shelter caterpillars, and so to occupy the niche longer and exploit Cecropia resources before colonization by ants. However, once incipient ant colonies are able to develop, they prevent further colonization by the caterpillars. Although no higher herbivory rates were noted, these caterpillars are ineffective in protecting their host trees from a pathogenic fungus, Fusarium moniliforme (Deuteromycetes), that develops on the trichilium in the absence of mutualistic ants. Therefore, the Cecropia treelets can be parasitized by two often overlooked species: the caterpillars that shelter in the domatia and feed on FBs, delaying colonization by mutualistic ants, and the fungal pathogen that develops on old trichilia. The cost of greater FB production plus the presence of the pathogenic fungus likely affect tree growth

Mutation in utp15 Disrupts Vascular Patterning in a p53-Dependent Manner in Zebrafish Embryos

Angiogenesis is the process by which the highly branched and functional vasculature arises from the major vessels, providing developing tissues with nutrients, oxygen, and removing metabolic waste. During embryogenesis, vascular patterning is dependent on a tightly regulated balance between pro- and anti-angiogenic signals, and failure of angiogenesis leads to embryonic lethality. Using the zebrafish as a model organism, we sought to identify genes that influence normal vascular patterning.In a forward genetic screen, we identified mutant LA1908, which manifests massive apoptosis during early embryogenesis, abnormal expression of several markers of arterial-venous specification, delayed angiogenic sprouting of the intersegmental vessels (ISV), and malformation of the caudal vein plexus (CVP), indicating a critical role for LA1908 in cell survival and angiogenesis. Genetic mapping and sequencing identified a G to A transition in the splice site preceding exon 11 of utp15 in LA1908 mutant embryos. Overexpression of wild type utp15 mRNA suppresses all observed mutant phenotypes, demonstrating a causative relationship between utp15 and LA1908. Furthermore, we found that injecting morpholino oligonucleotides inhibiting p53 translation prevents cell death and rescues the vascular abnormalities, indicating that p53 is downstream of Utp15 deficiency in mediating the LA1908 phenotypes.Taken together, our data demonstrate an early embryonic effect of Utp15 deficiency on cell survival and the normal patterning of the vasculature and highlight an anti-angiogenic role of p53 in developing embryos

Do you get what you pay for? Sales incentives and implications for motivation and changes in turnover intention and work effort

This study investigated relations between pay-for-performance incentives designed to vary in instrumentality (annual pay-for-performance, quarterly pay-for-performance, and base pay level) and employee outcomes (self-reported work effort and turnover intention) in a longitudinal study spanning more than 2 years. After controlling for perceived instrumentality, merit pay increase, and the initial values of the dependent variables, the amount of base pay was positively related to work effort and negatively related to turnover intention, where both relationships were mediated by autonomous motivation. The amounts of quarterly and annual pay-for-performance were both positively related to controlled motivation, but were differently related to the dependent variables due to different relations with autonomous motivation

Millennials in the Workplace: A Communication Perspective on Millennials’ Organizational Relationships and Performance

Stereotypes about Millennials, born between 1979 and 1994, depict them as self-centered, unmotivated, disrespectful, and disloyal, contributing to widespread concern about how communication with Millennials will affect organizations and how they will develop relationships with other organizational members. We review these purported characteristics, as well as Millennials’ more positive qualities—they work well in teams, are motivated to have an impact on their organizations, favor open and frequent communication with their supervisors, and are at ease with communication technologies. We discuss Millennials’ communicated values and expectations and their potential effect on coworkers, as well as how workplace interaction may change Millennials

Malaria Parasite Invasion of the Mosquito Salivary Gland Requires Interaction between the Plasmodium TRAP and the Anopheles Saglin Proteins

SM1 is a twelve-amino-acid peptide that binds tightly to the Anopheles salivary gland and inhibits its invasion by Plasmodium sporozoites. By use of UV-crosslinking experiments between the peptide and its salivary gland target protein, we have identified the Anopheles salivary protein, saglin, as the receptor for SM1. Furthermore, by use of an anti-SM1 antibody, we have determined that the peptide is a mimotope of the Plasmodium sporozoite Thrombospondin Related Anonymous Protein (TRAP). TRAP binds to saglin with high specificity. Point mutations in TRAP's binding domain A abrogate binding, and binding is competed for by the SM1 peptide. Importantly, in vivo down-regulation of saglin expression results in strong inhibition of salivary gland invasion. Together, the results suggest that saglin/TRAP interaction is crucial for salivary gland invasion by Plasmodium sporozoites

Pseudomonas aeruginosa PilY1 Binds Integrin in an RGD- and Calcium-Dependent Manner

PilY1 is a type IV pilus (tfp)-associated protein from the opportunistic pathogen Pseudomonas aeruginosa that shares functional similarity with related proteins in infectious Neisseria and Kingella species. Previous data have shown that PilY1 acts as a calcium-dependent pilus biogenesis factor necessary for twitching motility with a specific calcium binding site located at amino acids 850–859 in the 1,163 residue protein. In addition to motility, PilY1 is also thought to play an important role in the adhesion of P. aeruginosa tfp to host epithelial cells. Here, we show that PilY1 contains an integrin binding arginine-glycine-aspartic acid (RGD) motif located at residues 619–621 in the PilY1 from the PAK strain of P. aeruginosa; this motif is conserved in the PilY1s from the other P. aeruginosa strains of known sequence. We demonstrate that purified PilY1 binds integrin in vitro in an RGD-dependent manner. Furthermore, we identify a second calcium binding site (amino acids 600–608) located ten residues upstream of the RGD. Eliminating calcium binding from this site using a D608A mutation abolished integrin binding; in contrast, a calcium binding mimic (D608K) preserved integrin binding. Finally, we show that the previously established PilY1 calcium binding site at 851–859 also impacts the protein's association with integrin. Taken together, these data indicate that PilY1 binds to integrin in an RGD- and calcium-dependent manner in vitro. As such, P. aeruginosa may employ these interactions to mediate host epithelial cell binding in vivo

The development of sex differences in ring-tailed lemur feeding ecology

Sex differences in feeding ecology may develop in response to fluctuations in physiological costs to females over their reproductive cycles, or to sexual size dimorphism, or function to minimize feeding competition within a group via resource partitioning. For most mammal species, it is unknown how these factors contribute to sex differences in feeding, or how the development of males and females reflects these intraspecific feeding differences. We show changes in dietary composition, diversity, overlap, and foraging behavior throughout development in ring-tailed lemurs (Lemur catta) and test how the development of sex differences in feeding is related to female costs of reproduction and year-round resource partitioning. Sex differences in dietary composition were only present when females were lactating, but sex differences in other aspects of feeding, including dietary diversity, and relative time spent feeding and foraging, developed at or near the time of weaning. Sex difference in juveniles and subadults, when present, were similar to the differences found in adults. The low year-round dietary overlap and early differences in dietary diversity indicate that some resource partitioning may begin with young individuals and fluctuate throughout development. The major differences between males and females in dietary composition suggest that these larger changes in diet are closely tied to female reproductive state when females must shift their diet to meet energetic and nutritional requirements

Stranger to Familiar: Wild Strepsirhines Manage Xenophobia by Playing

The power of play in limiting xenophobia is a well-known phenomenon in humans. Yet, the evidence in social animals remains meager. Here, we aim to determine whether play promotes social tolerance toward strangers in one of the most basal group of primates, the strepsirhines. We observed two groups of wild lemurs (Propithecus verreauxi, Verreaux's sifaka) during the mating season. Data were also collected on nine visiting, outgroup males. We compared the distribution of play, grooming, and aggressive interactions across three conditions: OUT (resident/outgroup interactions), IN (resident/resident interactions in presence of outgroups) and BL-IN (baseline of resident/resident interactions in absence of outgroups). Play frequency between males was higher in OUT than in IN and BL-IN conditions; whereas, grooming was more frequent in IN than in OUT and BL-IN conditions. Aggression rates between resident and outgroup males were significantly higher than those between residents. However, aggressions between resident and outgroup males significantly decreased after the first play session and became comparable with resident-resident aggression levels. The presence of strangers in a well-established group implies the onset of novel social circumstances, which sifaka males cope with by two different tactics: grooming with ingroup males and playing with outgroup ones. The grooming peak, concurrently with the visit of outgroups, probably represents a social shield adopted by resident males to make their pre-existing affiliation more evident to the stranger “audience”. Being mostly restricted to unfamiliar males, adult play in sifaka appears to have a role in managing new social situations more than in maintaining old relationships. In particular, our results indicate not only that play is the interface between strangers but also that it has a specific function in reducing xenophobia. In conclusion, play appears to be an ice-breaker mechanism in the critical process that “upgrades” an individual from stranger to familiar

In Silico Identification of Specialized Secretory-Organelle Proteins in Apicomplexan Parasites and In Vivo Validation in Toxoplasma gondii

Apicomplexan parasites, including the human pathogens Toxoplasma gondii and Plasmodium falciparum, employ specialized secretory organelles (micronemes, rhoptries, dense granules) to invade and survive within host cells. Because molecules secreted from these organelles function at the host/parasite interface, their identification is important for understanding invasion mechanisms, and central to the development of therapeutic strategies. Using a computational approach based on predicted functional domains, we have identified more than 600 candidate secretory organelle proteins in twelve apicomplexan parasites. Expression in transgenic T. gondii of eight proteins identified in silico confirms that all enter into the secretory pathway, and seven target to apical organelles associated with invasion. An in silico approach intended to identify possible host interacting proteins yields a dataset enriched in secretory/transmembrane proteins, including most of the antigens known to be engaged by apicomplexan parasites during infection. These domain pattern and projected interactome approaches significantly expand the repertoire of proteins that may be involved in host parasite interactions