Showing papers by "Washington State University published in 1999"
TL;DR: In this article, a strong positive correlation between changes in institutional ownership and returns measured over the same period was found, which suggests that either institutional investors positive-feedback trade more than individual investors or institutional herding impacts prices more than herding by individual investors.
Abstract: We document strong positive correlation between changes in institutional ownership and returns measured over the same period. The result suggests that either institutional investors positive-feedback trade more than individual investors or institutional herding impacts prices more than herding by individual investors. We find evidence that both factors play a role in explaining the relation. We find no evidence, however, of return mean-reversion in the year following large changes in institutional ownership—stocks institutional investors purchase subsequently outperform those they sell. Moreover, institutional herding is positively correlated with lag returns and appears to be related to stock return momentum. HERDING AND FEEDBACK TRADING HAVE THE POTENTIAL to explain a number of financial phenomena, such as excess volatility, momentum, and reversals in stock prices. Herding is a group of investors trading in the same direction over a period of time; feedback trading involves correlation between herding and lag returns. 1 Although a recent growing body of literature is devoted to investor herding and feedback trading, extant studies take divergent paths. One path depicts individual investors as engaging in herding as a result of irrational, but systematic, responses to fads or sentiment. A second path depicts institutional investors engaging in herding as a result of agency problems, security characteristics, fads, or the manner in which information is impounded in the market.
1,542 citations
TL;DR: This work has shown that most polyploid species examined, both plant and animal, have formed recurrently from different populations of their progenitors, potentially producing new gene complexes and facilitating rapid evolution.
Abstract: Polyploidy has played a major role in the evolution of many eukaryotes. Recent studies have dramatically reshaped views of polyploid evolution, demonstrating that most polyploid species examined, both plant and animal, have formed recurrently from different populations of their progenitors. Populations of independent origin can subsequently come into contact and hybridize, generating new genotypes. Because of the frequency of polyploidy in plants, many recognized species are probably polyphyletic. Extensive and rapid genome restructuring can occur after polyploidization. Such changes can be mediated by transposons. Polyploidization could represent a period of transilience, during which genomic changes occur, potentially producing new gene complexes and facilitating rapid evolution.
1,010 citations
05 Jan 1999
TL;DR: A new theory called a theory of media synchronicity is described which proposes that a set of five media capabilities are important to group work, and that all tasks are composed of two fundamental communication processes.
Abstract: The paper describes a new theory called a theory of media synchronicity which proposes that a set of five media capabilities are important to group work, and that all tasks are composed of two fundamental communication processes (conveyance and convergence). Communication effectiveness is influenced by matching the media capabilities to the needs of the fundamental communication processes, not aggregate collections of these processes (i.e., tasks) as proposed by media richness theory. The theory also proposes that the relationships between communication processes and media capabilities will vary between established and newly formed groups, and will change over time.
847 citations
TL;DR: Genetic reprogramming of peptide and polyketide synthetases has been successful, and portions of the coronatine and syringomycin gene clusters could be valuable resources in developing new antimicrobial agents.
Abstract: Coronatine, syringomycin, syringopeptin, tabtoxin, and phaseolotoxin are the most intensively studied phytotoxins of Pseudomonas syringae, and each contributes significantly to bacterial virulence in plants. Coronatine functions partly as a mimic of methyl jasmonate, a hormone synthesized by plants undergoing biological stress. Syringomycin and syringopeptin form pores in plasma membranes, a process that leads to electrolyte leakage. Tabtoxin and phaseolotoxin are strongly antimicrobial and function by inhibiting glutamine synthetase and ornithine carbamoyltransferase, respectively. Genetic analysis has revealed the mechanisms responsible for toxin biosynthesis. Coronatine biosynthesis requires the cooperation of polyketide and peptide synthetases for the assembly of the coronafacic and coronamic acid moieties, respectively. Tabtoxin is derived from the lysine biosynthetic pathway, whereas syringomycin, syringopeptin, and phaseolotoxin biosynthesis requires peptide synthetases. Activation of phytotoxin synthesis is controlled by diverse environmental factors including plant signal molecules and temperature. Genes involved in the regulation of phytotoxin synthesis have been located within the coronatine and syringomycin gene clusters; however, additional regulatory genes are required for the synthesis of these and other phytotoxins. Global regulatory genes such as gacS modulate phytotoxin production in certain pathovars, indicating the complexity of the regulatory circuits controlling phytotoxin synthesis. The coronatine and syringomycin gene clusters have been intensively characterized and show potential for constructing modified polyketides and peptides. Genetic reprogramming of peptide and polyketide synthetases has been successful, and portions of the coronatine and syringomycin gene clusters could be valuable resources in developing new antimicrobial agents.
842 citations
TL;DR: The cumulative data suggest that systemic wound signals that induce PG activity and H2O2 are widespread in the plant kingdom and that the response may be associated with the defense of plants against both herbivores and pathogens.
Abstract: Hydrogen peroxide (H2O2) generated in response to wounding can be detected at wound sites and in distal leaf veins within 1 hr after wounding. The response is systemic and maximizes at about 4–6 hr in both wounded and unwounded leaves, and then declines. The timing of the response corresponds with an increase in wound-inducible polygalacturonase (PG) mRNA and enzyme activity previously reported, suggesting that oligogalacturonic acid (OGA) fragments produced by PG are triggering the H2O2 response. Systemin, OGA, chitosan, and methyl jasmonate (MJ) all induce the accumulation of H2O2 in leaves. Tomato plants transformed with an antisense prosystemin gene produce neither PG activity or H2O2 in leaves in response to wounding, implicating systemin as a primary wound signal. The antisense plants do produce both PG activity and H2O2 when supplied with systemin, OGA, chitosan, or MJ. A mutant tomato line compromised in the octadecanoid pathway does not exhibit PG activity or H2O2 in response to wounding, systemin, OGA, or chitosan, but does respond to MJ, indicating that the generation of H2O2 requires a functional octadecanoid signaling pathway. Among 18 plant species from six families that were assayed for wound-inducible PG activity and H2O2 generation, 14 species exhibited both wound-inducible PG activity and the generation of H2O2. Four species, all from the Fabaceae family, exhibited little or no wound-inducible PG activity and did not generate H2O2. The time course of wound-inducible PG activity and H2O2 in Arabidopsis thaliana leaves was similar to that found in tomato. The cumulative data suggest that systemic wound signals that induce PG activity and H2O2 are widespread in the plant kingdom and that the response may be associated with the defense of plants against both herbivores and pathogens.
807 citations
TL;DR: The results of parsimony analyses of DNA sequences of the plastid genes rbcL and atpB and the nuclear 18S rDNA for 560 species of angiosperms and seven non-flowering seed plants are reported and show a well-resolved and well-supported phylogenetic tree for the angios perms for use in comparative biology.
Abstract: Comparative biology requires a firm phylogenetic foundation to uncover and understand patterns of diversification and evaluate hypotheses of the processes responsible for these patterns. In the angiosperms, studies of diversification in floral form, stamen organization, reproductive biology, photosynthetic pathway, nitrogen-fixing symbioses and life histories have relied on either explicit or implied phylogenetic trees. Furthermore, to understand the evolution of specific genes and gene families, evaluate the extent of conservation of plant genomes and make proper sense of the huge volume of molecular genetic data available for model organisms such as Arabidopsis, Antirrhinum, maize, rice and wheat, a phylogenetic perspective is necessary. Here we report the results of parsimony analyses of DNA sequences of the plastid genes rbcL and atpB and the nuclear 18S rDNA for 560 species of angiosperms and seven non-flowering seed plants and show a well-resolved and well-supported phylogenetic tree for the angiosperms for use in comparative biology.
782 citations
TL;DR: This study demonstrates that Amboreella, Nymphaeales and Illiciales-Trimeniaceae-Austrobaileya represent the first stage of angiosperm evolution, with Amborella being sister to all other angiosperms, and shows that Gnetales are related to the conifers and are not sister to the angios perms, thus refuting the Anthophyte Hypothesis.
Abstract: Angiosperms have dominated the Earth's vegetation since the mid-Cretaceous (90 million years ago), providing much of our food, fibre, medicine and timber, yet their origin and early evolution have remained enigmatic for over a century. One part of the enigma lies in the difficulty of identifying the earliest angiosperms; the other involves the uncertainty regarding the sister group of angiosperms among extant and fossil gymnosperms. Here we report a phylogenetic analysis of DNA sequences of five mitochondrial, plastid and nuclear genes (total aligned length 8,733 base pairs), from all basal angiosperm and gymnosperm lineages (105 species, 103 genera and 63 families). Our study demonstrates that Amborella, Nymphaeales and Illiciales-Trimeniaceae-Austrobaileya represent the first stage of angiosperm evolution, with Amborella being sister to all other angiosperms. We also show that Gnetales are related to the conifers and are not sister to the angiosperms, thus refuting the Anthophyte Hypothesis. These results have far-reaching implications for our understanding of diversification, adaptation, genome evolution and development of the angiosperms.
779 citations
TL;DR: A large conformational change of a ∼15-amino-acid region (the neck linker) in kinesin is detected and visualized using electron paramagnetic resonance, fluorescence resonance energy transfer, pre-steady state kinetics and cryo-electron microscopy.
Abstract: Kinesin motors power many motile processes by converting ATP energy into unidirectional motion along microtubules. The force-generating and enzymatic properties of conventional kinesin have been extensively studied; however, the structural basis of movement is unknown. Here we have detected and visualized a large conformational change of an approximately 15-amino-acid region (the neck linker) in kinesin using electron paramagnetic resonance, fluorescence resonance energy transfer, pre-steady state kinetics and cryo-electron microscopy. This region becomes immobilized and extended towards the microtubule 'plus' end when kinesin binds microtubules and ATP, and reverts to a more mobile conformation when gamma-phosphate is released after nucleotide hydrolysis. This conformational change explains both the direction of kinesin motion and processive movement by the kinesin dimer.
771 citations
TL;DR: Interruptions were found to improve decision-making performance on simple tasks and to lower performance on complex tasks, and the frequency of interruptions and the dissimilarity of content between the primary and interruption tasks was found to exacerbate this effect.
Abstract: Interruptions are a common aspect of the work environment of most organizations. Yet little is known about how interruptions and their characteristics, such as frequency of occurrence, influence decision-making performance of individuals. Consequently, this paper reports the results of two experiments investigating the influence of interruptions on individual decision making. Interruptions were found to improve decision-making performance on simple tasks and to lower performance on complex tasks. For complex tasks, the frequency of interruptions and the dissimilarity of content between the primary and interruption tasks was found to exacerbate this effect. The implications of these results for future research and practice are discussed.
672 citations
TL;DR: A detailed literature review of semi-active control systems is provided in this article, which provides references to both theoretical and experimental research but concentrates on describing the results of experimental work, focusing on descriptions of the dynamic behavior and distinguishing features of various systems which have been experimentally tested both at the component level and within small-scale structural models.
656 citations
TL;DR: Long‐term field studies of the same interaction across multiple communities and spatially structured mathematical models are together beginning to show that coevolution may be a more important ongoing process than had been indicated by earlier empirical and theoretical studies lacking a geographic perspective.
Abstract: Coevolution is one of the major processes organizing the earth's biodiversity. The need to understand coevolution as an ongoing process has grown as ecological concerns have risen over the dynamics of rapidly changing biological communities, the conservation of genetic diversity, and the population biology of diseases. The biggest current challenge is to understand how coevolution operates across broad geographic landscapes, linking local ecological processes with phylogeographic patterns. The geographic mosaic theory of coevolution provides a framework for asking how coevolution continually reshapes interactions across different spatial and temporal scales. It produces specific hypotheses on how geographically structured coevolution differs from coevolution at the local scale. It also provides a framework for understanding how local maladaptation can result from coevolution and why coevolved interactions may rarely produce long lists of coevolved traits that become fixed within species. Long‐te...
TL;DR: In this article, the authors examine how self-processes and trust influence the development of commitment in society, thereby making social order possible, and test the self-verification-commitment process with respect to the spousal identity for newly married couples during the first three years of their marriage.
Abstract: This research examines how self-processes and trust influence the development of commitment in society, thereby making social order possible. The central thesis is that the process ofself-verification leads directly and indirectly, through positive emotions and trust, to the development of committed relationships, positive emotional attachments, and a group orientation; all of these are characteristics of a stable social structure. At the same time, self-verification results in the accomplishment of the meaning structures and resource flows that define social structures. In the current study, we test the self-verification-commitment process with respect to the spousal identity for newly married couples during the first three years of their marriage. The results support the central thesis and underscore the importance of self-processes and trust in building and maintaining social structure.
TL;DR: In this paper, the authors investigated the strategic role of interfirm relationships through the concept of strategic integration and found that dependence, flexibility, continuity expectations, and relationship age encouraged the distributor's strategic integration of its supplier relationship.
Abstract: This study investigates the strategic role of interfirm relationships through the concept of strategic integration. Following the conceptual development of strategic integration, the author reports a study of its antecedents and performance outcomes. Uncertainty was expected to have contextual effects in the development and outcomes of strategic integration in industrial distribution channels. A survey of industrial equipment distributors revealed that dependence, flexibility, continuity expectations, and relationship age encouraged the distributor's strategic integration of its supplier relationship. In addition, strategic integration enhanced distributor financial performance. However, uncertainty did not play a role in the distributors' strategic integration of their supplier relationships nor its effect on performance.
TL;DR: A brief introduction to lithic analysis can be found in this article, where the authors discuss the basics of stone tool production and debitage attributes of a stone tool and its relationships with other artifacts.
Abstract: 1. A brief introduction to lithic analysis 2. Basics of stone tool production 3. Lithic raw materials 4. Getting started in lithic analysis: identification and classification 5. Flake debitage attributes 6. Approaches to debitage analysis 7. Approaches to stone tool analysis 8. Artifact diversity and site function 9. Lithic analysis and prehistoric sedentism 10. Concluding remarks.
TL;DR: A 0–1 mixed integer programming model is presented that simultaneously solves for the location of remanufacturing/distribution facilities, the transshipment, production, and stocking of the optimal quantities of re manufactured products and cores.
Abstract: Recoverable product environments are becoming an increasingly important segment of the overall push in industry towards environmentally conscious manufacturing. Integral to the recoverable product environment is the recoverable manufacturing system that focuses on recovering the product and extending its life through remanufacture or repair. Remanufacturing provides the customer with an opportunity to acquire a product that meets the original product standards at a lower price than a new product. The flow of materials and products in this environment occurs both from the customer to the remanufacturer (reverse flow), and from the remanufacturer to the customer (forward flow). Since most of the products and materials may be conserved, essentially this forms a closed-loop logistics system. We present a 0–1 mixed integer programming model that simultaneously solves for the location of remanufacturing/distribution facilities, the transshipment, production, and stocking of the optimal quantities of remanufactured products and cores. We also discuss the managerial uses of the model for logistics decision-making.
TL;DR: Logistic regression, discriminant analysis, and neural networks were used to predict ordered and disordered regions in proteins to support the hypothesis that disorder is encoded by the amino acid sequence.
Abstract: Logistic regression (LR), discriminant analysis (DA), and neural networks (NN) were used to predict ordered and disordered regions in proteins. Training data were from a set of non-redundant X-ray crystal structures, with the data being partitioned into N-terminal, C-terminal and internal (I) regions. The DA and LR methods gave almost identical 5-cross validation accuracies that averaged to the following values: 75.9 +/- 3.1% (N-regions), 70.7 +/- 1.5% (I-regions), and 74.6 +/- 4.4% (C-regions). NN predictions gave slightly higher scores: 78.8 +/- 1.2% (N-regions), 72.5 +/- 1.2% (I-regions), and 75.3 +/- 3.3% (C-regions). Predictions improved with length of the disordered regions. Averaged over the three methods, values ranged from 52% to 78% for length = 9-14 to >/= 21, respectively, for I-regions, from 72% to 81% for length = 5 to 12-15, respectively, for N-regions, and from 70% to 80% for length = 5 to 12-15, respectively, for C-regions. These data support the hypothesis that disorder is encoded by the amino acid sequence.
TL;DR: Nitrogen and argon isotopes in trapped air in Greenland ice show that the Greenland Summit warmed 9 +/- 3 degrees C over a period of several decades, beginning 14,672 years ago, supporting a North Atlantic rather than a tropical trigger for the climate event.
Abstract: The last glacial period was terminated by an abrupt warming event in the North Atlantic ∼15,000 years before the present, and warming events of similar age have been reported from low latitudes. Understanding the mechanism of this termination requires that the precise relative timing of abrupt climate warming in the tropics versus the North Atlantic be known. Nitrogen and argon isotopes in trapped air in Greenland ice show that the Greenland Summit warmed 9 ± 3°C over a period of several decades, beginning 14,672 years ago. Atmospheric methane concentrations rose abruptly over a ∼50-year period and began their increase 20 to 30 years after the onset of the abrupt Greenland warming. These data suggest that tropical climate became warmer or wetter (or both) ∼20 to 80 years after the onset of Greenland warming, supporting a North Atlantic rather than a tropical trigger for the climate event.
TL;DR: Induced oleoresinosis in grand fir (Abies grandis) provides a model system for studying the regulation of defensive terpene biosynthesis and for identifying relevant genes.
TL;DR: It is shown that the concerted activation of Tyro 3, Axl and Mer in Sertoli cells is critical to the role that these cells play as nurturers of developing germ cells.
Abstract: We have generated and analysed null mutations in the mouse genes encoding three structurally related receptors with tyrosine kinase activity: Tyro 3, Axl, and Mer Mice lacking any single receptor, or any combination of two receptors, are viable and fertile, but male animals that lack all three receptors produce no mature sperm, owing to the progressive death of differentiating germ cells This degenerative phenotype appears to result from a failure of the tropic support that is normally provided by Sertoli cells of the seminiferous tubules, whose function depends on testosterone and additional factors produced by Leydig cells Tyro 3, Axl and Mer are all normally expressed by Sertoli cells during postnatal development, whereas their ligands, Gas6 and protein S, are produced by Leydig cells before sexual maturity, and by both Leydig and Sertoli cells thereafter Here we show that the concerted activation of Tyro 3, Axl and Mer in Sertoli cells is critical to the role that these cells play as nurturers of developing germ cells Additional observations indicate that these receptors may also be essential for the tropic maintenance of diverse cell types in the mature nervous, immune and reproductive systems
TL;DR: This paper found that students who wrote arguments from the web sources gained a better understanding than other students, even when information was presented as an argument, and showed that argument writing produced the most integrated and causal essays with the most transformation from the original sources.
Abstract: In 2 experiments, understanding of historical subject matter was enhanced when students acted as historians and constructed their own models of an historical event. Providing students with information in a web site with multiple sources instead of a textbook chapter, and instructing them to write arguments instead of narratives, summaries, or explanations, produced the most integrated and causal essays with the most transformation from the original sources. Better performance on inference and analogy tasks provided converging evidence that students who wrote arguments from the web sources gained a better understanding than other students. A second experiment replicated the advantage of argument writing even when information was presented as an argument.
TL;DR: Cucurbita maxima (CmPP16) was cloned and the protein was shown to possess properties similar to those of viral movement proteins as mentioned in this paper, which is likely required to mediate RNA delivery into the long-distance translocation stream.
Abstract: CmPP16 from Cucurbita maxima was cloned and the protein was shown to possess properties similar to those of viral movement proteins. CmPP16 messenger RNA (mRNA) is present in phloem tissue, whereas protein appears confined to sieve elements (SE). Microinjection and grafting studies revealed that CmPP16 moves from cell to cell, mediates the transport of sense and antisense RNA, and moves together with its mRNA into the SE of scion tissue. CmPP16 possesses the characteristics that are likely required to mediate RNA delivery into the long-distance translocation stream. Thus, RNA may move within the phloem as a component of a plant information superhighway.
TL;DR: The hypothesis tested in the current study was that kit-ligand/stem cell factor (KL) promotes the initiation and progression of primordial follicle development in the ovary.
Abstract: Initiation of folliculogenesis through the induction of primordial follicle development in the ovary has an important role in determining the fertility and reproductive fitness of most mammalian species. The factors that control this critical process are largely unknown. The hypothesis tested in the current study was that kit-ligand/stem cell factor (KL) promotes the initiation and progression of primordial follicle development in the ovary. Ovaries from 4-day-old rats were maintained in organ culture for 5 and 14 days and treated with no factor (control), recombinant kit-ligand (KL), or gonadotropins (FSH and hCG). Follicles in ovarian sections were counted and histologically classified as primordial (stage 0), early primary (stage 1), primary (stage 2), transitional (stage 3), or preantral (stage 4). Fresh ovaries from 4-day-old rats contained 68% primordial follicles (stage 0) and 32% developing follicles (stages 1-4) per section. After 5 and 14 days in culture, section from control ovaries contained approximately 41% and 55%, respectively, developing follicles (stage 1-4) per section due to spontaneous development of primordial follicles. Spontaneous primordial follicle development was completely blocked by ACK-2, a c-kit antibody that blocks KL actions. This observation suggests that endogenous KL is necessary for primordial follicle development in vitro. After 14 days of KL treatment, sections from ovaries contained 17% primordial follicles (stage 0) and 83% developing follicles (stage 1-4) per section demonstrating a dramatic induction of primordial follicle development by KL. Gonadotropins (FSH and hCG) did not induce primordial follicle development but did increase the percentage of preantral follicles (stage 4) per section. This small increase in preantral follicles in response to gonadotropins was blocked by ACK-2 suggesting that KL may in part mediate gonadotropin actions after the initiation of primordial follicle development. Ovaries contained an average of 309+/-10 follicles per section. The total number of follicles per section did not significantly vary between treatments suggesting that the effects of KL were not due to an alteration in follicle number (i.e. survival). KL appears to be one of the first factors identified to be involved in the promotion of primordial follicle development. Results suggest that KL is necessary and sufficient to induce primordial follicle development and initiate folliculogenesis.
TL;DR: The authors examined the relationship between institutional influences and stakeholder representation on boards of directors and found that variations in legal environments, industry regulation, and firm size are associated with the adoption of stakeholder-oriented board committees.
Abstract: This study examined the relationships between institutional influences and stakeholder representation on boards of directors. Data from 224 companies over the period 1984–94 were employed. Results indicate that variations in legal environments, industry regulation, and firm size are associated with stakeholder representation on boards but do not influence stakeholder representation on key board committees. Legal environments and firm size are associated with the adoption of stakeholder-oriented board committees.
TL;DR: A successful strategy for installing the key biochemical component of the C4 pathway of photosynthesis in C3 plants by introducing the intact gene of maize phosphoenolpyruvate carboxylase into transgenic rice plants.
Abstract: Using an Agrobacterium-mediated transformation system, we have introduced the intact gene of maize phosphoenolpyruvate carboxylase (PEPC), which catalyzes the initial fixation of atmospheric CO2 in C4 plants into the C3 crop rice. Most transgenic rice plants showed high-level expression of the maize gene; the activities of PEPC in leaves of some transgenic plants were two- to threefold higher than those in maize, and the enzyme accounted for up to 12% of the total leaf soluble protein. RNA gel blot and Southern blot analyses showed that the level of expression of the maize PEPC in transgenic rice plants correlated with the amount of transcript and the copy number of the inserted maize gene. Physiologically, the transgenic plants exhibited reduced O2 inhibition of photosynthesis and photosynthetic rates comparable to those of untransformed plants. The results demonstrate a successful strategy for installing the key biochemical component of the C4 pathway of photosynthesis in C3 plants.
TL;DR: This work describes how interspecific interactions can evolve rapidly over decades, blurring the distinction between evolutionary time and ecological time and making the study of coevolution crucial for human health and welfare.
Abstract: Interactions between species are as evolutionarily malleable as the species themselves and have played a central role in the diversification and organization of life. This malleability creates complex geographic mosaics in interspecific interactions that can evolve rapidly over decades, blurring the distinction between evolutionary time and ecological time and making the study of coevolution crucial for human health and welfare.
TL;DR: The effects of blanching and high hydrostatic pressure (HHP) treatments on natural flora evolution, polyphenoloxidase (PPO) activity and color of banana puree adjusted to pH 3.4 and water activity (a w ) of 0.97 were evaluated during 15 days storage at 25°C as discussed by the authors.
Abstract: The effects of blanching and high hydrostatic pressure (HHP) treatments on natural flora evolution, polyphenoloxidase (PPO) activity and color of banana puree adjusted to pH 3.4 and water activity (a w ) of 0.97 were evaluated during 15 days storage at 25°C. Standard plate as well as yeast and mold counts of HHP treated purees were <10 CFU/g throughout storage. Blanching time was found to affect (p<0.05) puree color. HHP treatments retained the initial color of the banana purees. Longer browning induction times and slower browning rates were observed when a longer blanching time was combined with a 689 MPa pressure treatment. A residual PPO activity < 5% was observed in the puree when a 7 min blanch was followed by HHP treatment at 689 MPa for 10 min.
TL;DR: Expression in Escherichia coli of phlA, phlC,phlB, andphlD, individually or in combination, identified a novel polyketide biosynthetic pathway in which PhlD is responsible for the production of monoacetylphloroglucinol (MAPG).
Abstract: The polyketide metabolite 2,4-diacetylphloroglucinol (2,4-DAPG) is produced by many strains of fluorescent Pseudomonas spp. with biocontrol activity against soilborne fungal plant pathogens. Genes required for 2,4-DAPG synthesis by P. fluorescens Q2-87 are encoded by a 6.5-kb fragment of genomic DNA that can transfer production of 2,4-DAPG to 2,4-DAPG-nonproducing recipient Pseudomonas strains. In this study the nucleotide sequence was determined for the 6.5-kb fragment and flanking regions of genomic DNA from strain Q2-87. Six open reading frames were identified, four of which (phlACBD) comprise an operon that includes a set of three genes (phlACB) conserved between eubacteria and archaebacteria and a gene (phlD) encoding a polyketide synthase with homology to chalcone and stilbene synthases from plants. The biosynthetic operon is flanked on either side by phlE and phlF, which code respectively for putative efflux and regulatory (repressor) proteins. Expression in Escherichia coli of phlA, phlC, phlB, and phlD, individually or in combination, identified a novel polyketide biosynthetic pathway in which PhlD is responsible for the production of monoacetylphloroglucinol (MAPG). PhlA, PhlC, and PhlB are necessary to convert MAPG to 2,4-DAPG, and they also may function in the synthesis of MAPG.
TL;DR: In this model, in intact plants under permissive conditions, photosynthesis is regulated so that lumen pH remains mod erate, where it modulates the activity of the violaxanthin deepoxidase, does not significantly restrict the turnover of the cytochrome b6f complex, and does not destabilize the oxygen evolving complex.
Abstract: Proton motive force (pmf), established across the thylakoid membrane by photosynthetic electron transfer, functions both to drive the synthesis of ATP and initiate processes that down-regulate photosynthesis. At the same time, excessively low lumen pH can lead to the destruction of some lumenal components and sensitization of the photosynthetic apparatus to photoinhibition. Therefore, in order to understand the energy budget of photosynthesis, its regulation and responses to environmental stresses, it is essential to know the magnitude of pmf, its distribution between ΔpH and the electric field (Δϕ) as well as the relationships between these parameters and ΔGATP, and down-regulatory and inhibitory processes. We review past estimates of lumen pH and propose a model that can explain much of the divergent data in the literature. In this model, in intact plants under permissive conditions, photosynthesis is regulated so that lumen pH remains mod erate (between 5.8 and 6.5), where it modulates the activity of the violaxanthin deepoxidase, does not significantly restrict the turnover of the cytochrome b6f complex, and does not destabilize the oxygen evolving complex. Only under stressed conditions, where light input exceeds the capacity of both photosynthesis and down-regulatory processes, does lumen pH decrease below 5, possibly contributing to photoinhibition. A value of n = 4 for the stoichiometry of protons pumped through the ATP synthase per ATP synthesized, and a minor contribution of Δϕ to pmf, will allow moderate lumen pH to sustain the observed levels of ΔGATP.
TL;DR: Tin may serve as a molecular blueprint for sarcomere assembly and turnover by specifying the precise position of its ligands within each half-sarcomere in addition to functioning as a Molecular spring that maintains the structural integrity of the contracting myofibrils.