Social attraction in video-mediated communication: The role of nonverbal affiliative behavior.

The first aim of this study was to analyze video-mediated communication (VMC), in comparison to face-to-face (FTF) communication, and the effect it has on how communicators express nonverbal affiliative behaviors relevant for social attraction. Second, this study aimed to discover whether these nonverbal expressions relate to communicators' social attraction. An experiment with 93 cross-sex dyads was conducted, with a get-acquainted exercise in a VMC or a FTF condition. Our findings revealed that communicators in VMC smiled more and spoke louder. In addition, VMC interactants displayed less facial touching than FTF interactants. Finally, more gaze aversion and a higher speech rate were found to influence social attraction. These findings have implications for research on cue-rich computer-mediated communication (CMC) and the way in which communicators nonverbally express themselves in comparison to copresent FTF communication. Additionally, this study has implications for social information processing theory which may be extended to include cue-rich forms of CMC.

Genetic Diversity of Fusarium oxysporum f. sp. cubense in East and Central Africa.

Banana Fusarium wilt is a major production constraint globally and a significant threat to the livelihoods of millions of people in East and Central Africa (ECA). A proper understanding of the diversity and population dynamics of the causal agent, Fusarium oxysporum f. sp. cubense (Foc), could be useful for the development of sustainable disease management strategies for the pathogen. The current study investigated the diversity of Foc in ECA using vegetative compatibility group (VCG) analysis, PCR-RFLPs of the ribosomal DNA's intergenic spacer region, as well as phylogenetic analysis of the elongation factor-1α gene. Six VCGs (0124, 0125, 0128, 01212, 01220, and 01222), which all belong to one lineage (Foc lineage VI), were widely distributed throughout the region. VCGs 0128 and 01220 are reported for the first time in Burundi, the Democratic Republic of Congo (DRC), Rwanda, Tanzania, and Uganda, while VCG 01212 is reported in the DRC and Rwanda. Isolates that did not belong to any of the known VCGs were identified as Foc lineage VI members by phylogenetic analysis and may represent novel VCGs. CAV 2734, a banana pathogen collected in Rwanda, clustered with nonpathogenic F. oxysporum isolates in lineage VIII. Results from this study will contribute significantly toward the implementation of banana Fusarium wilt disease management practices in the region, such as the restricted movement of infected planting material and the selective planting of resistant banana varieties.

The application of Arabidopsis thaliana in studying tripartite interactions among plants, beneficial fungal endophytes and biotrophic plant-parasitic nematodes.

MAIN CONCLUSION: The research demonstrated that Arabidopsis can be used as a model system for studying plant-nematode-endophyte tripartite interactions; thus, opening new possibilities for further characterizing the molecular mechanisms behind these interactions. Arabidopsis has been established as an important model system for studying plant biology and plant-microbe interactions. We show that this plant can also be used for studying the tripartite interactions among plants, the root-knot nematode Meloidogyne incognita and a beneficial endophytic isolate of Fusarium oxysporum, strain Fo162. In various plant species, Fo162 can systemically reduce M. incognita infection development and fecundity. Here it is shown that Fo162 can also colonize A. thaliana roots without causing disease symptoms, thus behaving as a typical endophyte. As observed for other plants, this endophyte could not migrate from the roots into the shoots and leaves. Direct inoculation of the leaves also did not result in colonization of the plant. A significant increase in plant fresh weight, root length and average root diameter was observed, suggesting the promotion of plant growth by the endophyte. The inoculation of A. thaliana with F. oxysporum strain Fo162 also resulted in a significant reduction in the number of M. incognita juveniles infecting the roots and ultimately the number of galls produced. This was also observed in a split-root experiment, in which the endophyte and nematode were spatially separated. The usefulness of Arabidopsis opens new possibilities for further dissecting complex tripartite interactions at the molecular and biochemical level.

Abutilon theophrasti's defense against the allelochemical benzoxazolin-2(3H)-one: support by Actinomucor elegans.

Abutilon theophrasti Medik., previously found to be rather insensitive to benzoxazinoid containing rye mulch and the allelochemical benzoxazolin-2(3H)-one (BOA), can be associated with the zygomycete Actinomucor elegans, whereby the fungus colonizes the root relatively superficially and mainly in the maturation zone. The fungus mitigates necrosis of the cotyledons when seedlings are incubated with 2 mM BOA, in contrast to those that lack the fungus. In liquid cultures of the fungus, tryptophan was identified. The accumulation of tryptophan is increased in presence of BOA. This amino acid seems to be important in protecting Abutilon against BOA and its derivatives since it suppressed the accumulation of BOA derived, highly toxic 2-aminophen-oxazin-3-one (APO) in the medium and on the root surface during BOA incubations of Abutilon seedlings. Although A. elegans is insensitive to BOA and APO, the fungus is not able to protect the plant against harmful effects of APO, when seedlings are treated with the compound. Abutilon can detoxify BOA via BOA-6-OH glucosylation probably by a cell wall associated glucosyltransferase, but only low amounts of the product accumulate. Low tryptophan concentrations can contribute to a degradation of the toxic intermediate BOA-6-OH by Fenton reactions, whereby the amino acid is oxidized. One of the oxidation products was identified as 4(1H)-quinolinone, which is the core substructure of the quorum sensing molecule 2-heptyl-3-hydroxy-4-quinolone. The mutualistic association of Abutilon theophrasti with Actinomucor elegans is considered as opportunistic and facultative. Such plant-fungus associations depend rather likely on environmental conditions, such as the mode of fertilization.

Originality in online dating profile texts: How does perceived originality affect impression formation and what makes a text original?

This paper investigates origins and consequences of perceived profile text originality. The first goal was to examine whether the perceived originality of authentic online dating profile texts affects online daters' perceptions of attractiveness, and whether perceptions of (less) desired partner personality traits mediate this effect. Results showed the positive impact of perceived profile text originality on impression formation: text originality positively affects perceptions of intelligence and sense of humor, which improve impressions of attractiveness and boost dating intention. The second goal was to explore what profile text features increase perceptions of profile text originality. Results revealed profile texts which were stylistically original (e.g., include metaphors) and contained more and concrete self-disclosure statements were considered more original, explaining almost half of the variance in originality scores. Taken together, our results suggest that perceived originality in profile texts is manifested in both meaning and form, and is a balancing act between novelty and appropriateness.

Isolation and characterization of fenamiphos degrading bacteria.

The biological factors responsible for the microbial breakdown of the organophosphorus nematicide fenamiphos were investigated. Microorganisms responsible for the enhanced degradation of fenamiphos were isolated from soil that had a long application history of this nematicide. Bacteria proved to be the most important group of microbes responsible for the fenamiphos biodegradation process. Seventeen bacterial isolates utilized the pure active ingredient fenamiphos as a carbon source. Sixteen isolates rapidly degraded the active ingredient in Nemacur 5GR. Most of the fenamiphos degrading bacteria were Microbacterium species, although Sinorhizobium, Brevundimonas, Ralstonia and Cupriavidus were also identified. This array of gram positive and gram negative fenamiphos degrading bacteria appeared to be pesticide-specific, since cross-degradation toward fosthiazate, another organophosphorus pesticide used for nematode control, did not occur. It was established that the phylogenetical relationship among nematicide degrading bacteria is closer than that to non-degrading isolates.

Shifts in banana root exudate profiles after colonization with the non-pathogenic Fusarium oxysporum strain Fo162.

The non-pathogenic fungus Fusorium oxysporum strain Fo162 can efficiently colonize banana roots and reduce infecting by the burrowing nematode Radopholus similis. It is assumed that the fungus triggers a systemic reaction in the plant, which is affecting the biochemical composition of the root exudates and is thus causing the reduction in nematode colonization. To characterize these shifts, a continuous flow experiment was set up to collect root metabolites on a matrix (XAD-4). Based on HPLC analysis, the extracts, collected from the XAD-4, showed no differences in the composition of the root exudates between plants colonized by the endophyte and the controls. However, the accumulation of several compounds differed significantly. When these extracts were used in a bioassay with Radopholus similis none of the sample-treatment combinations had a significant attracting or repelling effect on the nematodes. This experiment shows that non-pathogenic Fusarium oxysporum strain Fo162 is able to upregulate the synthesis of at least some, so far unidentified compounds released by banana roots under hydroponic conditions. Further studies and optimization of the experimental setup are required to determine whether or not increase in metabolite concentration can affect nematode responses in vitro and ultimately in vivo.

Involvement of microorganisms other than pseudomonad's on the degradation of the non-fumigant organophosphate nematicide fenamiphos.

Fenamiphos is a broad spectrum, non-volatile, systemic, organophosphorus nematicide extensively used throughout the world to control plant-parasitic nematodes. The efficacy of this nematicide can decrease in soils where microorganisms accumulate that are capable of rapidly degrading the active ingredient. Among the documented microorganisms to degrade organophosphate compounds, Pseudomonas spp. was frequently identified. However, it still not clear whether or not this bacterial genus is the major responsible one in the biodegradation process. Our objective was to study the roll of Pseudomonas spp. and other soil bacteria on the degradation of fenamiphos in soils with different nematicide application history. In some of these soils fenamiphos metabolizing microorganisms were found, whereas in others not. For example, a soil with 42 fenamiphos applications during 16 years neither contained Pseudomonas spp. nor biodegrading microorganisms. In two different soils, both with 25 fenamiphos applications in 12 years and containing metabolizing microorganisms, only one of them contained Pseudomonas spp., demonstrating that the nematicide was rapidly metabolized by microorganisms other than Pseudomonas spp. Conversely, a control soil, with no previous nematicide application history, contained the highest number of Pseudomonas spp. of all soils analyzed. The number of bacteria of this genus could be increased when compost was added, although this did not alter the lack of the fenamiphos degradation process, even after six weeks and three consecutive nematicide treatments. The Pseudomonas diversity of the non-degrading control soil was composed of P. putida (50%), P. fluorescens (31%), P. syringae (13%) and P. chlororaphis (6%) according to gas chromatography identification. Individual analysis of the Pseudomonas spp. bacteria showed that none were capable of metabolizing fenamiphos in vitro. In conclusion, we demonstrated that Pseudomonas spp. are not intrinsically capable of fenamiphos metabolization. We also found that Pseudomonas spp. may not always accumulate upon fenamiphos treatment and that there are other microorganisms able to metabolize this nematicide.

Involvement of the ABC transporter BcAtrB and the laccase BcLCC2 in defence of Botrytis cinerea against the broad-spectrum antibiotic 2,4-diacetylphloroglucinol.

The genetic and biochemical basis of defence mechanisms in plant pathogenic fungi against antifungal compounds produced by antagonistic microorganisms is largely unknown. The results of this study show that both degradative and non-degradative defence mechanisms enable the plant pathogenic fungus Botrytis cinerea to resist the broad-spectrum, phenolic antibiotic 2,4-diacetylphloroglucinol (2,4-DAPG). The efflux pump BcAtrB provides the first line of defence for B. cinerea, preventing accumulation of 2,4-DAPG in the cell to toxic concentrations, whereas the extracellular laccase BcLCC2 mediates, via conversion of tannic acid, subsequent degradation of 2,4-DAPG. Expression of BcatrB is induced by 2,4-DAPG and efflux gives B. cinerea sufficient time to more effectively initiate the process of BcLCC2-mediated antibiotic degradation. This is supported by the observations that the BcatrB mutant is significantly more sensitive to 2,4-DAPG than its parental strain, and is substantially less effective in 2,4-DAPG degradation. The results of this study further showed that BcLCC2 itself is not able to degrade 2,4-DAPG, but requires tannic acid as a mediator for 2,4-DAPG degradation. To our knowledge, this is the first time that the laccase-mediator system is shown to play a role in the detoxification of a broad-spectrum antibiotic compound from bacterial origin. We postulate that yet unknown constituents present in tannic acid act as substrate(s) of BcLCC2, thereby generating radicals that mediate 2,4-DAPG degradation.

Early biotic stress detection in tomato (Solanum lycopersicum) by BVOC emissions.

We investigated impacts of early and mild biotic stress on Biogenic Volatile Organic Compounds (BVOC) emissions from tomato in order to test their potential for early (biotic) stress detection. Tomato plants were exposed to two common fungal pathogens, Botrytis cinerea and Oidium neolycopesici and the sap-sucking aphid Myzus persicae. Furthermore, plants were exposed to methyl jasmonate (MeJA) in order to identify BVOC emissions related to activation of jasmonic acid (JA) signalling pathway. These emissions where then used as a reference for identifying active JA signalling pathway in plants at early stages of biotic stress. After infection by the necrotrophic fungus B. cinerea, changes in BVOC emissions indicated that tomato plants had predominantly activated the jasmonic acid (JA) signalling pathway. The plants were able to modify their defence pathways in order to overcome fungal infection. When tomato plants were infected with the biotrophic fungus O. neolycopersici, only minor changes in BVOC emissions were observed with additional emissions of the sesquiterpene α-copaene. α-copaene emissions allowed the identification of general biotic stress in the plants, without pinpointing the actual triggered defence pathway. BVOC emissions during M. persicae attack had changed before the occurrence of visual symptoms. Despite low infestation rates, plants emitted methyl salicylate indicating activation of the SA-mediated defence pathway.

Bioactive secondary metabolites with multiple activities from a fungal endophyte.

In order to replace particularly biohazardous nematocides, there is a strong drive to finding natural product-based alternatives with the aim of containing nematode pests in agriculture. The metabolites produced by the fungal endophyte Fusarium oxysporum 162 when cultivated on rice media were isolated and their structures elucidated. Eleven compounds were obtained, of which six were isolated from a Fusarium spp. for the first time. The three most potent nematode-antagonistic compounds, 4-hydroxybenzoic acid, indole-3-acetic acid (IAA) and gibepyrone D had LC50 values of 104, 117 and 134 µg ml-1 , respectively, after 72 h. IAA is a well-known phytohormone that plays a role in triggering plant resistance, thus suggesting a dual activity, either directly, by killing or compromising nematodes, or indirectly, by inducing defence mechanisms against pathogens (nematodes) in plants. Such compounds may serve as important leads in the development of novel, environmental friendly, nematocides.

Pathogen self-defense: mechanisms to counteract microbial antagonism,.

Natural and agricultural ecosystems harbor a wide variety of microorganisms that play an integral role in plant health, crop productivity, and preservation of multiple ecosystem functions. Interactions within and among microbial communities are numerous and range from synergistic and mutualistic to antagonistic and parasitic. Antagonistic and parasitic interactions have been exploited in the area of biological control of plant pathogenic microorganisms. To date, biocontrol is typically viewed from the perspective of how antagonists affect pathogens. This review examines the other face of this interaction: how plant pathogens respond to antagonists and how this can affect the efficacy of biocontrol. Just as microbial antagonists utilize a diverse arsenal of mechanisms to dominate interactions with pathogens, pathogens have surprisingly diverse responses to counteract antagonism. These responses include detoxification, repression of biosynthetic genes involved in biocontrol, active efflux of antibiotics, and antibiotic resistance. Understanding pathogen self-defense mechanisms for coping with antagonist assault provides a novel approach to improving the durability of biologically based disease control strategies and has implications for the deployment of transgenes (microorganisms or plants).

Characteristics and motives of adolescents talking with strangers on the internet.

Despite widespread concerns about the dangers of adolescents' online communication with strangers, we know little about (a) which types of adolescents talk with strangers and (b) what motivates them to do so. Drawing on a survey among 412 Dutch adolescents, we found that early adolescents (12-14-year-olds) were most prone to talk with strangers on the internet. If adolescents communicated online more frequently, they less often talked with strangers on the internet. However, if adolescents engaged in long chat sessions, they tended to talk with strangers on the internet more often. In contrast to earlier research, introversion was not related to adolescents' tendency to talk with strangers. The motives of entertainment, meeting new people, and social compensation increased adolescents' online communication with strangers.

Friend networking sites and their relationship to adolescents' well-being and social self-esteem.

The aim of this study was to investigate the consequences of friend networking sites (e.g., Friendster, MySpace) for adolescents' self-esteem and well-being. We conducted a survey among 881 adolescents (10-19-year-olds) who had an online profile on a Dutch friend networking site. Using structural equation modeling, we found that the frequency with which adolescents used the site had an indirect effect on their social self-esteem and well-being. The use of the friend networking site stimulated the number of relationships formed on the site, the frequency with which adolescents received feedback on their profiles, and the tone (i.e., positive vs. negative) of this feedback. Positive feedback on the profiles enhanced adolescents' social self-esteem and well-being, whereas negative feedback decreased their self-esteem and well-being.

Mechanisms Involved in Nematode Control by Endophytic Fungi.

Colonization of plants by particular endophytic fungi can provide plants with improved defenses toward nematodes. Evidently, such endophytes can be important in developing more sustainable agricultural practices. The mechanisms playing a role in this quantitative antagonism are poorly understood but most likely multifactorial. This knowledge gap obstructs the progress regarding the development of endophytes or endophyte-derived constituents into biocontrol agents. In part, this may be caused by the fact that endophytic fungi form a rather heterogeneous group. By combining the knowledge of the currently characterized antagonistic endophytic fungi and their effects on nematode behavior and biology with the knowledge of microbial competition and induced plant defenses, the various mechanisms by which this nematode antagonism operates or may operate are discussed. Now that new technologies are becoming available and more accessible, the currently unresolved mechanisms can be studied in greater detail than ever before.

Developing a model of adolescent friendship formation on the internet.

Previous research has been largely silent about what precisely influences online friendship formation and has ignored motives for online communication as potential explanations. Drawing on a sample of 493 adolescents, this study tested a path model of adolescent friendship formation including as predictors introversion/extraversion, online self-disclosure, motive for social compensation, and frequency of online communication. Our path analysis showed that extraverted adolescents self-disclosed and communicated online more frequently, which, in turn, facilitated the formation of online friendships. Introverted adolescents, by contrast, were more strongly motivated to communicate online to compensate for lacking social skills. This increased their chances of making friends online. Among introverted adolescents, a stronger motive for social compensation also led to more frequent online communication and online self-disclosure, resulting in more online friendships. The model suggests that the antecedents of online friendship formation are more complex than previously assumed and that motives for online communication should be studied more closely.

Defense responses of Fusarium oxysporum to 2,4-diacetylphloroglucinol, a broad-spectrum antibiotic produced by Pseudomonas fluorescens.

A collection of 76 plant-pathogenic and 41 saprophytic Fusarium oxysporum strains was screened for sensitivity to 2,4-diacetylphloroglucinol (2,4-DAPG), a broad-spectrum antibiotic produced by multiple strains of antagonistic Pseudomonas fluorescens. Approximately 17% of the F. oxysporum strains were relatively tolerant to high 2,4-DAPG concentrations. Tolerance to 2,4-DAPG did not correlate with the geographic origin of the strains, formae speciales, intergenic spacer (IGS) group, or fusaric acid production levels. Biochemical analysis showed that 18 of 20 tolerant F. oxysporum strains were capable of metabolizing 2,4-DAPG. For two tolerant strains, analysis by mass spectrometry indicated that deacetylation of 2,4-DAPG to the less fungitoxic derivatives monoacetylphloroglucinol and phloroglucinol is among the initial mechanisms of 2,4-DAPG degradation. Production of fusaric acid, a known inhibitor of 2,4-DAPG biosynthesis in P. fluorescens, differed considerably among both 2,4-DAPG-sensitive and -tolerant F. oxysporum strains, indicating that fusaric acid production may be as important for 2,4-DAPG-sensitive as for -tolerant F. oxysporum strains. Whether 2,4-DAPG triggers fusaric acid production was studied for six F. oxysporum strains; 2,4-DAPG had no significant effect on fusaric acid production in four strains. In two strains, however, sublethal concentrations of 2,4-DAPG either enhanced or significantly decreased fusaric acid production. The implications of 2,4-DAPG degradation, the distribution of this trait within F. oxysporum and other plant-pathogenic fungi, and the consequences for the efficacy of biological control are discussed.

Information sharing and relationships on social networking sites.

This article investigates the relationship between sharing personal information and relationship development in the context of social networking sites (SNSs). Information disclosed on these sites could affect relationships in a different manner compared to more traditional interactions, such as instant messaging or face-to-face interaction. Respondents in the age range of 12 to 83 were surveyed about experiences of relationship development as a consequence of contact through Facebook or Hyves-the most popular Dutch SNSs. Results showed a primarily positive effect of information sharing on SNSs on our relationships. Furthermore, relationship development mainly occurs among acquaintances and friends, and public posts are most strongly related to relationship development. These findings suggest that SNSs might affect relationships in a distinct fashion as acquaintances and friends gain access to public self-disclosures that might normally only be reserved for close friends and family. Overall, this study provides an insight into some of the positive aspects of the public nature of SNSs in contrast with the general negative associations.

Phytotoxic Nep1-like proteins from the necrotrophic fungus Botrytis cinerea associate with membranes and the nucleus of plant cells.

Nep1-like proteins (NLPs), produced by an array of unrelated microorganisms, are phytotoxic for dicotyledonous plant cells but their mode of action has not yet been established. Two paralogous NLPs from the necrotrophic plant pathogenic fungus Botrytis cinerea were characterized, designated BcNEP1 and BcNEP2. Both proteins were produced in the heterologous host Pichia pastoris and purified to homogeneity. The localization of fluorescently labelled proteins was studied and mechanisms of cell death were investigated in protoplasts and suspension cells. Purified BcNEP1 and BcNEP2 caused necrosis in all dicotyledonous plant species tested, but not in monocotyledons. A synthetic heptapeptide comprising a sequence (GHRHDWE) that is conserved in all NLPs did not cause symptoms and was unable to interfere with necrosis induction by BcNEP1 and BcNEP2 proteins. Fluorescently labelled BcNEP1 and BcNEP2 proteins were associated with plasma membranes and the nuclear envelope, as well as in the nucleolus of responding plant cells. A strong hydrogen peroxide (H(2)O(2)) accumulation was observed in chloroplasts. The death process was characterized by TUNEL assays as apoptosis, necrosis or intermediate forms of both. BcNEP1- and BcNEP2-induced cell death execution could not be abolished by specific inhibitors. These results provide further information on mechanisms of NLP-inflicted cell death.

Functional analysis of NLP genes from Botrytis elliptica.

SUMMARY We functionally analysed two Nep1-like protein (NLP) genes from Botrytis elliptica (a specialized pathogen of lily), encoding proteins homologous to the necrosis and ethylene-inducing protein (NEP1) from Fusarium oxysporum. Single gene replacement mutants were made for BeNEP1 and BeNEP2, providing the first example of transformation and successful targeted mutagenesis in this fungus. The virulence of both mutants on lily leaves was not affected. BeNEP1 and BeNEP2 were individually expressed in the yeast Pichia pastoris, and the necrosis-inducing activity was tested by infiltration of both proteins into leaves of several monocots and eudicots. Necrotic symptoms developed on the eudicots tobacco, Nicotiana benthamiana and Arabidopsis thaliana, and cell death was induced in tomato cell suspensions. No necrotic symptoms developed on leaves of the monocots rice, maize and lily. These results support the hypothesis that the necrosis-inducing activity of NLPs is limited to eudicots. We conclude that NLPs are not essential virulence factors and they do not function as host-selective toxins for B. elliptica.