191 research outputs found
Interaction ammonium-nitrate: Response to oxidative stress in chicory plants
No full textThe aim of this work was to study, as a function of the different availability of nitrogen in the reduced form, mineral and organic, the induction of the synthesis of some ROS-scavenging molecules and the evolution of some enzymatic activities such as ascorbate peroxidase (APX) and polyphenoloxidase (PPO). 
Chicory seedlings were grown in nutritive solution for 35 days in controlled conditions. On the 14th day, one third of the plants was transferred into a nutritive solution containing (NH4)2SO4 60 mM, one third was transferred into a medium containing Urea 60 mM, and the remaining was let grow into the nutrition solution, as a control. Three samplings of leaves were performed, respectively after 21, 28 and 35 days of growth.
The urea and ammonium sulphate-treated samples showed higher ascorbic acid and polyphenol contents than the control, together with a lower anthocyanins content. APX showed the highest activity in the urea-treated samples, while the highest PPO activity was to refer to samples treated with ammonium sulphate.
The variations of the organic components showed the incidence of the nitrogen supply in the reduced form on the cell redox potential, confirming the importance of fertilization for obtaining high amounts of antioxidant molecules.

Characterization of PPO-inhibitor resistance in waterhemp (Amaranthus tuberculatus) and Palmer amaranth (Amaranthus palmeri)
No full textWaterhemp and Palmer amaranth are two of the most troublesome weed species in the Midwest. The overuse of acetolactate synthase (ALS), photosystem II, and 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) inhibitors to control these species led to the evolution of resistance to these herbicides and, thus, protoporphyrinogen oxidase (PPO) inhibitors were used to help control these resistant weeds. Waterhemp was the first weed species to evolve resistance to PPO inhibitors, and Palmer amaranth evolved resistance ten years later. The first known mechanism for this resistance involves the deletion of a glycine codon corresponding to the 210th amino acid position (dG210) of the PPO enzyme (PPX2). Chapter 1 includes a literature review of the PPO enzyme, the mode of action of PPO-inhibiting herbicides, the biology of waterhemp and Palmer amaranth, and an overview of PPO-inhibitor resistance in these two species. Chapter 2 explores how resistance to PPO inhibitors evolved in a population each of waterhemp and Palmer amaranth growing in the same field. The results indicate that they did not hybridize with one another to pass on resistance, but that they each evolved resistance to PPO inhibitors independently via two different forms of convergent evolution. Chapter 3 further analyzes PPO-inhibitor-resistance evolution in these two species by characterizing the relative level of resistance to PPO inhibitors in Palmer amaranth and waterhemp conferred specifically by the dG210 mutation. The results suggested that Palmer amaranth is naturally more tolerant to PPO inhibitors than waterhemp when treated POST, giving it less of a selective advantage to evolve resistance. This could be why Palmer amaranth took long to evolve resistance to PPO inhibitors. Three different amino acid changes at a homologous site of PPX2 have conferred resistance to PPO-inhibiting herbicides in two weed species. Chapter 4 is aimed at exploring additional amino acid substitutions that could occur at this site to determine whether they can also confer resistance to PPO inhibitors. The effect of these substitutions coupled with the dG210 mutation was also tested. In vitro PPO enzyme assays were carried out to determine the level of resistance conferred by these modifications. Inhibitors used were lactofen, fomesafen, saflufenacil, and trifludimoxazin. Although some modifications rendered the enzyme inactive, most did not. The dG210 mutation and the double mutants conferred the highest levels of resistance to all of the inhibitors, and the single mutants all exhibited varying levels of resistance to the inhibitors. A transgenic E. coli cell line was used to test these enzyme modifications in a living system. It was found that all of the modifications were active when tested in vivo. The fifth and final chapter discusses concluding remarks and future research.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2021-05-01The student, Kathryn Lillie, accepted the attached license on 2019-04-23 at 14:05.The student, Kathryn Lillie, submitted this Thesis for approval on 2019-04-23 at 14:15.This Thesis was approved for publication on 2019-04-23 at 17:12.DSpace SAF Submission Ingestion Package generated from Vireo submission #13845 on 2019-08-22 at 15:07:53Made available in DSpace on 2019-08-23T20:36:07Z (GMT). No. of bitstreams: 2
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Exploring Reinforcement Learning for Constrained Wing Shape Optimization
No full textIn this paper, the Proximal Policy Optimization (PPO) algorithm is used to perform a constrained wing shape optimization. The PPO algorithm is a Machine Learning (ML) algorithm that improves itself by repeatedly performing the same optimization and learning from its results. The complete adaptation of the PPO framework to the design problem is detailed and evaluated. Not only was the PPO framework able to consistently optimize the wing 4% further than the Particle Swarm Optimization (PSO) algorithm, it was able to do so 35 times faster once the model is fully trained. The PPO framework was able to find more efficient wing shapes than the PSO framework. The trained PPO model was able to optimize the wing of other similar aircraft, even without direct retraining. These results illustrate that PPO could be a promising technique for automated aerospace design problems. Due to the significant training time of the ML approach, the PPO algorithm is not an effective replacement of traditional optimization algorithms for design problems where only a single optimization is required.Aerospace Engineerin
Distribution of polyphenol oxidase in cultured hyphae of coriolus versicolor. A wood decay fungus and partial purification of the enzyme, 1992
No full textCoriolus versicolor, a white-rot Basidiomycete, secretes lignocellulolytic enzymes and polyphenol oxidase (PPO). While the former degrade wood polymers, the latter converts diphenols to diquinones. Because C. versicolor can be batch-cultured, overproduction and enhanced secretion of agriculturally/commercially useful enzymes are feasible. Reported are attempts to: define the timed-appearances of intra- and extracellular PPO, achieve possible PPO substrate induction, ascertain its secretion route and partially purify extracellular PPO. Whereas two protein peaks (6 and 12 days in a 16 day time-course) were observed for dialyzed mycelial homogenates, PPO specific activity (spc. act.) rose between 4 and 12 days and then declined. Dialyzed growth medium protein content climbed from 6 to 15 days and the PPO spc. act. increased linearly from 4 to 15 days. When dialyzed 12 and 15 day media aliquots were added to assay mixtures containing 100 mM catechol, syringic acid or gallic acid, significant differences in PPO spc. act. between substrates were noted. Time-dependent catechol addition to medium resulted in hyphal growth inhibition at early log but stimulation at log, stationary and decline phases. Light-electron microscopies/biochemistry suggest the secretion route permitting its regulation. Scanning electron microscopy (SEM) demonstrated that the hyphal tip wall was morphologically different from that of the mature region. Transmission electron microscopy (TEM) of glutaralaldehyde pre- and 0s04 post-fixed hyphae revealed mitochondria, ER, ribosomes, vacuoles and osmiophilic bodies in the mature regions cytoplasm but electron lucent masses appressed to the plasmalemma in the growing tip. Centrifugation of homogenates of hyphae cultured 0-16 days followed by PPO assay revealed that the enzyme was particulate. To further delineate the route, both TEM substrate localization and immunoelectron microscopies were employed. Protein G chromatography of immunized rabbits serum yielded two peaks; one was ELISA-positive and UV-absorbing. Antibody was tagged with colloidal gold and SEM localized PPO outside the hyphal glucan matrix. Substrate localization involved interposing dihydroxyphenylalanine between pre- and post-fixations. Although electron dense reaction product occurred in hyphae, plasmolysis was observed. As for partial purification, medium dialysis followed by 0-30% (NH4)2S04 fractionation and subsequent 12,000 xg centrifugation yielded PPO within the supernatant and a loss of one of four proteins upon SDS-PAGE. While these yielded an enhanced PPO spc. act., subsequent DEAE chromatography did not. Gel filtration of authentic PPO and medium followed by PPO assay revealed similar elution profiles suggesting an effective purification step. These results indicate that PPO secretion is organelle-mediated and that extracellular PPO can be partially purified by conventional biochemistry
The first record of PPO and 4-way herbicide resistance in eastern Canada
No full textThis is the first record of PPO-inhibitor resistance in eastern Canada, and the second record of a glyphosate-resistant weed in Quebec. In 2016 and 2017, waterhemp seed was collected from 25 locations in Ontario or Quebec. Multiple-resistance to imazethapyr, atrazine, and glyphosate was confirmed in 80% of the seed lots screened. Additionally, between 2015 and 2017, waterhemp seed was collected from 74 locations in Ontario or Quebec and resistance to lactofen was confirmed in 28% of the seed lots screened.The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
Improving a Reinforcement Learning Negotiating Agent’s Performance by Extracting Information from the Opponent’s Sequence of Offers
No full textWith the prospects of decentralized multi-agent systems becoming more prevalent in daily life, automated negotiation agents have made their place in these collaborative settings. They are an approach to promote communication between the agents in reaching solutions that are better for all involved.Recent literature has shown great potential in using machine learning, particularly model-free deep reinforcement learning like Proximal Policy Optimization (PPO), to develop more performant automated negotiation strategies. This work focuses on using information from the opponent's sequence of offers in a bilateral negotiation to further improve a baseline PPO agent. This involves extracting and representing information from the opponent's sequence of offers into a state vector with a fixed dimension to modify the input to the agent's policy, and then comparing the utilities this modified agent achieves to the baseline PPO agent. Since there is a large variety of numerical measures to represent a sequence of offers, an ablation study is conducted to investigate the effectiveness of each.The modified agents consistently reached solutions that had higher social welfare, although the agent's own utility did not improve or diminish significantly in comparison to the base PPO agent.https://github.com/brenting/negotiation_PPO The repository containing all the code this paper used. The code for this specific paper was done in the 'sequence-of-offers-single-thread' branch.CSE3000 Research ProjectComputer Science and Engineerin
The ecological role of the root enzyme polyphenol oxidase in the invasive plant genus Bromus
No full textBiological invasions adversely affect and disrupt natural ecosystems at great economic costs. The vast body of theory and research focus on which factors advance these invasions and is geared toward understanding, prevention, and management of non-native species. Roots of grasses in the genus Bromus constitutively possess high levels of the enzyme polyphenol oxidase (PPO), a catalyst for the oxidation of phenolics into visible melanin-like compounds. Phenolic substrates for PPO are plant-produced secondary metabolites with phytotoxic allelopathic properties. Through the conversion of these harmful phenolics by PPO, we hypothesized PPO may be used as a defense mechanism against phenolic-allelopathic plants and thereby contribute to the competitive success of Bromus species, many of which are non-native invaders. To test these hypotheses, we first assayed a wide range of Poaceae (grass) species for root PPO activity with a focus on bromes. Results showed significantly higher PPO levels in invasives than non-invasives, suggesting the ability to produce high root PPO concentrations is a trait contributing to invasion potential of non-native species, an important corollary that may be a useful tool for identifying future invasives. Second, through phylogenetic reconstructions, phenetic PPO was phylogenetically tractable and was only present in two taxonomically distinct genera, hinting at a high-PPO ancestral condition, later lost by some genera. Third, we examined effects of allelopathic competitor species on PPO and non-PPO-producing grasses in direct competition and exposed to leachate and litter; experiments supported our hypothesis as (a) PPO-producer Bromus tolerated allelopathic phenolic Centaurea, (b) but non-PPO Festuca was suppressed, and (c) non-phenolic allelopathic Artemisia suppressed both PPO-Bromus and non-PPO-Festuca. Fourth, field surveys showed allelopathic plants further distances from Bromus than non-allelopathic plants. Finally, we exposed a range of grass species of variable PPO activity to the phenolic-allelochemical caffeic acid (CA). PPO was constitutively expressed, but the utility was weakly observed, possibly due to sub-toxic doses. Overall, we illustrate PPO as a novel defense against phenolic-allelochemicals and as a trait correlated to invasiveness, and highlight ongoing taxonomic classifications that may shed light on evolutionary understanding of selection benefits of PPO and grass evolution, which are agriculturally, economically, and environmentally important.Ph.D.Includes bibliographical referencesIncludes vitaby Kimberly L. Plan
Common ragweed (Ambrosia artemisiifolia L.) accessions in the Mid-Atlantic region resistant to ALS-, PPO-, and EPSPS-inhibiting herbicides
No full textThis article was originally published in Weed Technology. The version of record is available at: https://doi.org/10.1017/wet.2024.11. © The Author(s), 2024. Published by Cambridge University Press on behalf of Weed Science Society of AmericaCommon ragweed is a troublesome weed in many crops. Farmers and crop advisors in the coastal Mid-Atlantic region have reported inadequate control of common ragweed in soybean fields with glyphosate and other herbicide modes of action. To determine whether herbicide resistance was one of the causes of poor herbicide performance, 29 accessions from four states (Delaware, Maryland, New Jersey, and Virginia) where common ragweed plants survived herbicide applications and produced viable seeds were used for greenhouse screening. Common ragweed seedlings from those accessions were treated with multiple rates of cloransulam, fomesafen, or glyphosate, applied individually postemergence (POST). All accessions except one demonstrated resistance to at least one of the herbicides applied at twice the effective rate (2×), 17 accessions were two-way resistant (to glyphosate and cloransulam, or to glyphosate and fomesafen), and three-way resistance was present in eight accessions collected from three different states. Based on the POST study, five accessions were treated preemergence (PRE) with herbicides that inhibit acetolactate synthase (ALS), and two accessions were treated with herbicides that inhibit protoporphyrinogen oxidase (PPO). All accessions treated PRE with the ALS inhibitors chlorimuron or cloransulam demonstrated resistance at the 2× rates. Both accessions treated PRE with the PPO inhibitor sulfentrazone had survivors at the 2× rate. When the same accessions were treated PRE with fomesafen, one had survivors at the 2× rate, and one had survivors at the 1× rate. Results from these tests confirmed common ragweed with three-way resistance to POST herbicides is widespread in the region. In addition, this is the first confirmation that common ragweed accessions in the region are also resistant to ALS- or PPO-inhibiting herbicides when applied PRE.We thank William Bamka, Benjamin Beale, Todd Davis, Dylan Lynch, Matt Morris; Baylee Carr, and Dr. Sarah Hirsh for collecting and submitting samples. This research received no specific grant from any funding agency, commercial, or not-for-profit sectors. Mr. D’Amico and Dr. Ziegler are employed by FMC Corporation
Learning-based resilience guarantee for multi-UAV collaborative QoS management
No full textUnmanned and intelligent technologies are the future development trend in the business field. It is of great significance for the connotation analysis and application characterization of massive interactive data. Particularly, during major epidemics or disasters, how to provide business services safely and securely is crucial. Specifically, providing users with resilient and guaranteed communication services is a challenging business task when the communication facilities are damaged. Unmanned aerial vehicles (UAVs), with flexible deployment and high maneuverability, can be used to serve as aerial base stations (BSs) to establish emergency networks. However, it is challenging to control multiple UAVs to provide efficient and fair communication quality of service (QoS) to users due to their limited communication service capabilities. In this paper, we propose a learning-based resilience guarantee framework for multi-UAV collaborative QoS management. We formulate this problem as a partial observable Markov decision process and solve it with proximal policy optimization (PPO), which is a policy-based deep reinforcement learning method. A centralized training and decentralized execution paradigm is used, where the experience collected by all UAVs is used to train the shared control policy. Each UAV takes actions based on the partial environment information it observes. In addition, the design of the reward function considers the average and variance of the communication QoS of all users. Extensive simulations are conducted for performance evaluation. The simulation results indicate that (1) the trained policies can adapt to different scenarios and provide resilient and guaranteed communication QoS to users, (2) increasing the number of UAVs can compensate for the lack of service capabilities of UAVs, (3) when UAVs have local communication service capabilities, the policies trained with PPO have better performance compared with the policies trained with other algorithms.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Robot Dynamic
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