SOCIAL INFLUENCE IN TECHNOLOGY ADOPTION RESEARCH: A LITERATURE REVIEW AND RESEARCH AGENDA

Social influence has been shown to profoundly affect human behavior in general and technology adoption (TA) in particular. Over time, multiple definitions and measures of social influence have been introduced to the field of TA research, contributing to an increasingly fragmented landscape of constructs that challenges the conceptual integrity of the field. In this vein, this paper sets out to review how social influence has been conceptualized with regard to TA. In so doing, this paper hopes to inform researchers’ understanding of the construct, provide an overview of its myriad conceptualizations, constructively challenge extant approaches, and provide impulses for future research. A systematic review of the relevant literature uncovers that extant interpretations of social influence are 1) predominantly compliance-based and as such risk overlooking identification- and internalization-based effects, and 2) primarily targeted at the individual level, thereby neglecting the impact of socially rich environments. Building upon these insights, this paper develops an integrated perspective on social influence in TA research that encourages scholars to pursue a multi-theoretical understanding of social influence at the interface of users, social referents, and technology

Analysis of xylem sap proteins from Brassica napus

BACKGROUND: Substance transport in higher land plants is mediated by vascular bundles, consisting of phloem and xylem strands that interconnect all plant organs. While the phloem mainly allocates photoassimilates, the role of the xylem is the transport of water and inorganic nutrients from roots to all aerial plant parts. Only recently it was noticed that in addition to mineral salts, xylem sap contains organic nutrients and even proteins. Although these proteins might have important impact on the performance of above-ground organs, only a few of them have been identified so far and their physiological functions are still unclear. RESULTS: We used root-pressure xylem exudate, collected from cut Brassica napus stems, to extract total proteins. These protein preparations were then separated by high-resolution two-dimensional gel electrophoresis (2-DE). After individual tryptic digests of the most abundant coomassie-stained protein spots, partial peptide sequence information was deduced from tandem mass spectrometric (MS/MS) fragmentation spectra and subsequently used for protein identifications by database searches. This approach resulted in the identification of 69 proteins. These identifications include different proteins potentially involved in defence-related reactions and cell wall metabolism. CONCLUSION: This study provides a comprehensive overview of the most abundant proteins present in xylem sap of Brassica napus. A number of 69 proteins could be identified from which many previously were not known to be localized to this compartment in any other plant species. Since Brassica napus, a close relative of the fully sequenced model plant Arabidopsis thaliana, was used as the experimental system, our results provide a large number of candidate proteins for directed molecular and biochemical analyses of the physiological functions of the xylem under different environmental and developmental conditions. This approach will allow exploiting many of the already established functional genomic resources, like i.e. the large mutant collections, that are available for Arabidopsis

Phloem small RNAs, nutrient stress responses, and systemic mobility

<p>Abstract</p> <p>Background</p> <p>Nutrient availabilities and needs have to be tightly coordinated between organs to ensure a balance between uptake and consumption for metabolism, growth, and defense reactions. Since plants often have to grow in environments with sub-optimal nutrient availability, a fine tuning is vital. To achieve this, information has to flow cell-to-cell and over long-distance via xylem and phloem. Recently, specific miRNAs emerged as a new type of regulating molecules during stress and nutrient deficiency responses, and miR399 was suggested to be a phloem-mobile long-distance signal involved in the phosphate starvation response.</p> <p>Results</p> <p>We used miRNA microarrays containing all known plant miRNAs and a set of unknown small (s) RNAs earlier cloned from <it>Brassica </it>phloem sap <abbrgrp><abbr bid="B1">1</abbr></abbrgrp>, to comprehensively analyze the phloem response to nutrient deficiency by removing sulfate, copper or iron, respectively, from the growth medium. We show that phloem sap contains a specific set of sRNAs that is distinct from leaves and roots, and that the phloem also responds specifically to stress. Upon S and Cu deficiencies phloem sap reacts with an increase of the same miRNAs that were earlier characterized in other tissues, while no clear positive response to -Fe was observed. However, -Fe led to a reduction of Cu- and P-responsive miRNAs. We further demonstrate that under nutrient starvation miR399 and miR395 can be translocated through graft unions from wild type scions to rootstocks of the miRNA processing <it>hen1-1 </it>mutant. In contrast, miR171 was not transported. Translocation of miR395 led to a down-regulation of one of its targets in rootstocks, suggesting that this transport is of functional relevance, and that miR395, in addition to the well characterized miR399, could potentially act as a long-distance information transmitter.</p> <p>Conclusions</p> <p>Phloem sap contains a specific set of sRNAs, of which some specifically accumulate in response to nutrient deprivation. From the observation that miR395 and miR399 are phloem-mobile in grafting experiments we conclude that translocatable miRNAs might be candidates for information-transmitting molecules, but that grafting experiments alone are not sufficient to convincingly assign a signaling function.</p

Second-Order Digital Inequality: the Case of E-Commerce

“Second-order digital inequality describes that certain individuals profit less from digital opportunities not only due to limited access but also due to limited abilities to use information and communication technologies (ICT). This study extends research on second-order digital inequality to the realm of e-commerce. We introduce a novel conceptualization of effective, potentially beneficial, e-commerce use that encompasses two dimensions: (1) the diversity of e-commerce platforms used by an individual; (2) the degree to which an individual uses supporting e-commerce features. Building on technology acceptance theory and social psychology, we argue that socio-economically disadvantaged individuals are less likely to use e-commerce effectively than socio-economically advantaged individuals. We empirically test our hypotheses on clickstream data that tracks the online behavior of 2819 US e-commerce users for six month. Our findings reveal that, despite equal access, the socio-economically advantaged use e-commerce more effectively regarding both dimensions. Implications for research and practice are discussed

RNA-Mediated Gene Silencing Signals Are Not Graft Transmissible from the Rootstock to the Scion in Greenhouse-Grown Apple Plants Malus sp.

RNA silencing describes the sequence specific degradation of RNA targets. Silencing is a non-cell autonomous event that is graft transmissible in different plant species. The present study is the first report on systemic acquired dsRNA-mediated gene silencing of transgenic and endogenous gene sequences in a woody plant like apple. Transgenic apple plants overexpressing a hairpin gene construct of the gusA reporter gene were produced. These plants were used as rootstocks and grafted with scions of the gusA overexpressing transgenic apple clone T355. After grafting, we observed a reduction of the gusA gene expression in T355 scions in vitro, but not in T355 scions grown in the greenhouse. Similar results were obtained after silencing of the endogenous Mdans gene in apple that is responsible for anthocyanin biosynthesis. Subsequently, we performed grafting experiments with Mdans silenced rootstocks and red leaf scions of TNR31-35 in order to evaluate graft transmitted silencing of the endogenous Mdans. The results obtained suggested a graft transmission of silencing signals in in vitro shoots. In contrast, no graft transmission of dsRNA-mediated gene silencing signals was detectable in greenhouse-grown plants and in plants grown in an insect protection tent

The potential of sodium carbonate and Tiron extractions for the determination of silicon contents in plant samples—A method comparison using hydrofluoric acid digestion as reference

For the determination of silicon (Si) contents in plant materials several methods are in use, but as all of these methods exhibit specific advantages and drawbacks, none of them has become prevalent. Alkaline chemicals are widely used to extract Si from plant samples, because this method is comparably simple, fast, and cheap. However, a comprehensive method comparison between different alkaline extractions to different plant organs is still missing, as well as understanding of the relationship between Si content quantified with those methods and soil silicon availability. In our study we performed two different alkaline (sodium carbonate (Na2CO3) and Tiron) extractions to determine Si contents in husk and straw samples of winter wheat (Triticum aestivum). Results obtained from hydrofluoric (HF) acid digestion were used as reference as this method is assumed to completely dissolve Si in a plant material. We evaluated the efficacy of simple, single-step Na2CO3 and Tiron extractions in relation to complex, multistep HF extractions and analyzed the relationships between Si and phytolith contents in plant samples and plant available Si concentrations in corresponding soil samples. Irrespective of the plant material used (husk or straw) we found Tiron to be more efficient in Si extraction compared to Na2CO3. While Na2CO3 extractions systematically underestimated Si contents in the tested plant materials, the results of Tiron extractions were comparable to the results of HF digestions, at least for husk samples. Phytolith contents in plant samples were strongly positively correlated to Si contents obtained from extractions, especially in husk samples. Plant available Si in soil samples was also reflected best in husk Si contents. Based on our results we recommend the use of Tiron for the extraction of Si from plant materials as this method provided more reliable results compared to the Na2CO3 extraction

Adaptation of aphid stylectomy for analyses of proteins and mRNAs in barley phloem sap

Sieve tubes are transport conduits not only for photoassimilates but also for macromolecules and other compounds that are involved in sieve tube maintenance and systemic signalling. In order to gain sufficient amounts of pure phloem exudates from barley plants for analyses of the protein and mRNA composition, a previously described stylectomy set-up was optimized. Aphids were placed in sealed cages, which, immediately after microcauterization of the stylets, were flooded with water-saturated silicon oil. The exuding phloem sap was collected with a capillary connected to a pump. Using up to 30 plants and 600 aphids (Rhopalosiphum padi) in parallel, an average of 10 μl of phloem sap could be obtained within 6 h of sampling. In first analyses of the macromolecular content, eight so far unknown phloem mRNAs were identified by cDNA-amplified fragment length polymorphism. Transcripts in barley phloem exudates are related to metabolism, signalling, and pathogen defence, for example coding for a protein kinase and a pathogen- and insect-responsive WIR1A (wheat-induced resistance 1A)-like protein. Further, one-dimensional gel electrophoresis and subsequent partial sequencing by mass spectrometry led to the identification of seven major proteins with putative functions in stress responses and transport of mRNAs, proteins, and sugars. Two of the discovered proteins probably represent isoforms of a new phloem-mobile sucrose transporter. Notably, two-dimensional electrophoresis confirmed that there are >250 phloem proteins awaiting identification in future studies

Comparative analysis of non-autonomous effects of tasiRNAs and miRNAs in Arabidopsis thaliana

In plants, small interfering RNAs (siRNAs) can trigger a silencing signal that may spread within a tissue to adjacent cells or even systemically to other organs. Movement of the signal is initially limited to a few cells, but in some cases the signal can be amplified and travel over larger distances. How far silencing initiated by other classes of plant small RNAs (sRNAs) than siRNAs can extend has been less clear. Using a system based on the silencing of the CH42 gene, we have tracked the mobility of silencing signals initiated in phloem companion cells by artificial microRNAs (miRNA) and trans-acting siRNA (tasiRNA) that have the same primary sequence. In this system, both the ta-siRNA and the miRNA act at a distance. Non-autonomous effects of the miRNA can be triggered by several different miRNA precursors deployed as backbones. While the tasiRNA also acts non-autonomously, it has a much greater range than the miRNA or hairpin-derived siRNAs directed against CH42, indicating that biogenesis can determine the non-autonomous effects of sRNAs. In agreement with this hypothesis, the silencing signals initiated by different sRNAs differ in their genetic requirements

Repression of Flowering by the miR172 Target SMZ

The flowering repressors SMZ and FLM, members of the AP-2 and MADS domain transcription factor families, unexpectedly work together to regulate flowering time via their effects on expression of the FT gene