130 research outputs found

    Ethylene- and pathogen-inducible Arabidopsis acyl-CoA-binding protein 4 interacts with an ethylene-responsive element binding protein

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    Six genes encode proteins with acyl-CoA-binding domains in Arabidopsis thaliana. They are the small 10-kDa cytosolic acyl-CoA-binding protein (ACBP), membrane-associated ACBP1 and ACBP2, extracellularly-targeted ACBP3, and kelch-motif containing ACBP4 and ACBP5. Here, the interaction of ACBP4 with an A. thaliana ethylene-responsive element binding protein (AtEBP), identified in a yeast two-hybrid screen, was confirmed by co-immunoprecipitation. The subcellular localization of ACBP4 and AtEBP, was addressed using an ACBP4:DsRed red fluorescent protein fusion and a green fluorescent protein (GFP):AtEBP fusion. Transient expression of these autofluoresence-tagged proteins in agroinfiltrated tobacco leaves, followed by confocal laser scanning microscopy, indicated their co-localization predominantly at the cytosol which was confirmed by FRET analysis. Immuno-electron microscopy on Arabidopsis sections not only localized ACBP4 to the cytosol but also to the periphery of the nucleus upon closer examination, perhaps as a result of its interaction with AtEBP. Furthermore, the expression of ACBP4 and AtEBP in Northern blot analyses was induced by the ethylene precursor 1-aminocyclopropane-1-carboxylic acid, methyl jasmonate treatments, and Botrytis cinerea infection, suggesting that the interaction of ACBP4 and AtEBP may be related to AtEBP-mediated defence possibly via ethylene and/or jasmonate signalling

    How Do Different Motives for R&D Cooperation Affect Firm Performance? An Analysis Based on Swiss Micro Data

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    Starting point of our analysis is the empirical fact that firms pursue different goals when getting engaged in R&D collaborations, often more than one goal at the same time. Given that firms are driven by different motives for R&D cooperation, the aim of this article is to investigate the differences related to different motives with respect (a) to the factors influencing the likelihood of R&D cooperation as postulated by theory; and (b) to the impact of R&D cooperation on firm innovativeness and firm productivity. On the whole, distinguishing various cooperation motives appears to be fruitful because it allows more differentiated insights with respect to the importance of factors determining cooperation that would remain hidden behind the overall variable R&D cooperation yes/no. Not only R&D cooperation in general but also cooperation driven by each of the seven motives considered in this paper correlate positively with the sales share of innovative products. With respect to innovativeness the characterization of cooperation by the driving motive did not add much more insights that it could be gained through the overall variable R&D cooperation yes/no. Technology-motivated collaborative activities show a weaker tendency to positive direct effects on productivity than cost-motivated cooperation. In this case, the distinction of several cooperation motives yields some additional insights as compared to the overall cooperation variable

    Effects of APETALA2 on embryo, endosperm, and seed coat development determine seed size in Arabidopsis

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    Arabidopsis APETALA2 (AP2) controls seed mass maternally, with ap2 mutants producing larger seeds than wild type. Here, we show that AP2 influences development of the three major seed compartments: embryo, endosperm, and seed coat. AP2 appears to have a significant effect on endosperm development. ap2 mutant seeds undergo an extended period of rapid endosperm growth early in development relative to wild type. This early expanded growth period in ap2 seeds is associated with delayed endosperm cellularization and overgrowth of the endosperm central vacuole. The subsequent period of moderate endosperm growth is also extended in ap2 seeds largely due to persistent cell divisions at the endosperm periphery. The effect of AP2 on endosperm development is mediated by different mechanisms than parent-of-origin effects on seed size observed in interploidy crosses. Seed coat development is affected; integument cells of ap2 mutants are more elongated than wild type. We conclude that endosperm overgrowth and/or integument cell elongation create a larger postfertilization embryo sac into which the ap2 embryo can grow. Morphological development of the embryo is initially delayed in ap2 compared with wild-type seeds, but ap2 embryos become larger than wild type after the bent-cotyledon stage of development. ap2 embryos are able to fill the enlarged postfertilization embryo sac, because they undergo extended periods of cell proliferation and seed filling. We discuss potential mechanisms by which maternally acting AP2 influences development of the zygotic embryo and endosperm to repress seed size

    BOLITA, an Arabidopsis AP2/ERF-like transcription factor that affects cell expansion and proliferation/differentiation pathways

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    The BOLITA (BOL) gene, an AP2/ERF transcription factor, was characterized with the help of an activation tag mutant and overexpression lines in Arabidopsis and tobacco. The leaf size of plants overexpressing BOL was smaller than wild type plants due to a reduction in both cell size and cell number. Moreover, severe overexpressors showed ectopic callus formation in roots. Accordingly, global gene expression analysis using the overexpression mutant reflected the alterations in cell proliferation, differentiation and growth through expression changes in RBR, CYCD, and TCP genes, as well as genes involved in cell expansion (i.e. expansins and the actin remodeling factor ADF5). Furthermore, the expression of hormone signaling (i.e. auxin and cytokinin), biosynthesis (i.e. ethylene and jasmonic acid) and regulatory genes was found to be perturbed in bol-D mutant leave

    Knowledge Base, Exporting Activities, Innovation Openness and Innovation Performance: A SEM Approach Towards a Unifying Framework

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    In this paper we demonstrate the complexity that regulates the innovation-exports nexus. In particular we argue that innovation and exports should be treated as latent variables in order to account for as many facets possible thus, accounting for multifaceted heterogeneity. In this context, the role of innovation openness ought to be highlighted within a unified framework, as it is considered an additional activity of firms' knowledge creation strategy. In this line, innovation and exporting orientation are ruled by the firms' strategic mix comprised of internal knowledge creation processes and the diversity of innovation openness. Theoretical and empirical links between these major components are identified and measured employing a Structural Equation Modelling (SEM) approach on a sample of Greek R&D-active manufacturing firms. Empirical findings corroborate the complexity of relationships and indicate that the firms' knowledge base and open innovation strategy regulate via complementary and substitution relationships firms' innovation and export performance

    Control of Flowering and Cell Fate by LIF2, an RNA Binding Partner of the Polycomb Complex Component LHP1

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    Polycomb Repressive Complexes (PRC) modulate the epigenetic status of key cell fate and developmental regulators in eukaryotes. The chromo domain protein LIKE HETEROCHROMATIN PROTEIN1 (LHP1) is a subunit of a plant PRC1-like complex in Arabidopsis thaliana and recognizes histone H3 lysine 27 trimethylation, a silencing epigenetic mark deposited by the PRC2 complex. We have identified and studied an LHP1-Interacting Factor2 (LIF2). LIF2 protein has RNA recognition motifs and belongs to the large hnRNP protein family, which is involved in RNA processing. LIF2 interacts in vivo, in the cell nucleus, with the LHP1 chromo shadow domain. Expression of LIF2 was detected predominantly in vascular and meristematic tissues. Loss-of-function of LIF2 modifies flowering time, floral developmental homeostasis and gynoecium growth determination. lif2 ovaries have indeterminate growth and produce ectopic inflorescences with severely affected flowers showing proliferation of ectopic stigmatic papillae and ovules in short-day conditions. To look at how LIF2 acts relative to LHP1, we conducted transcriptome analyses in lif2 and lhp1 and identified a common set of deregulated genes, which showed significant enrichment in stress-response genes. By comparing expression of LHP1 targets in lif2, lhp1 and lif2 lhp1 mutants we showed that LIF2 can either antagonize or act with LHP1. Interestingly, repression of the FLC floral transcriptional regulator in lif2 mutant is accompanied by an increase in H3K27 trimethylation at the locus, without any change in LHP1 binding, suggesting that LHP1 is targeted independently from LIF2 and that LHP1 binding does not strictly correlate with gene expression. LIF2, involved in cell identity and cell fate decision, may modulate the activity of LHP1 at specific loci, during specific developmental windows or in response to environmental cues that control cell fate determination. These results highlight a novel link between plant RNA processing and Polycomb regulation

    The Impact of Functional Integration and Spatial Proximity on the Post-entry Performance of Knowledge Intensive Business Service Firms

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    Knowledge intensive business service firms (KIBS) are an important element of modern economies and thus attracting increasing interest in scientific research. In the existing literature it is argued that due to the important role of knowledge, innovation and userproducer interaction in the KIBS sector, functional integration and spatial proximity are particularly decisive for a firm?s development. Nevertheless, due to the absence of suitable micro data there is a lack of studies empirically analysing the impact of functional integration and regional proximity using micro firm data. Based upon newlyconducted firm micro data in three German metropolitan regions, this paper supplements the literature by giving a multivariate empirical analysis of the determinants of post-entry performance of KIBS. The results of the estimation of firm growth equations show that functional linkages to knowledge providers, customers and co-operation partners indeed matter for the performance of young KIBS. Regarding spatial proximity, however, especially a high diversification of geographical reach is proved to be crucial
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