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At least 217 records · Page 12

Rapid and efficient in planta genome editing in sorghum using foxtail mosaic virus‐mediated sgRNA delivery

SUMMARY The requirement of in vitro tissue culture for the delivery of gene editing reagents limits the application of gene editing to commercially relevant varieties of many crop species. To overcome this bottleneck, plant RNA viruses have been deployed as versatile tools for in planta delivery of recombinant RNA. Viral delivery of single‐guide RNAs (sgRNAs) to transgenic plants that stably express CRISPR‐associated (Cas) endonuclease has been successfully used for targeted mutagenesis in several dicotyledonous and few monocotyledonous plants. Progress with this approach in monocotyledonous plants is limited so far by the availability of effective viral vectors. We engineered a set of foxtail mosaic virus (FoMV) and barley stripe mosaic virus (BSMV) vectors to deliver the fluorescent protein AmCyan to track viral infection and movement in Sorghum bicolor . We further used these viruses to deliver and express sgRNAs to Cas9 and Green Fluorescent Protein (GFP) expressing transgenic sorghum lines, targeting Phytoene desaturase ( PDS ), Magnesium‐chelatase subunit I ( MgCh ), 4‐hydroxy‐3‐methylbut‐2‐enyl diphosphate reductase , orthologs of maize Lemon white1 ( Lw1 ) or GFP . The recombinant BSMV did neither infect sorghum nor deliver or express AmCyan and sgRNAs. In contrast, the recombinant FoMV systemically spread throughout sorghum plants and induced somatic mutations with frequencies reaching up to 60%. This mutagenesis led to visible phenotypic changes, demonstrating the potential of FoMV for in planta gene editing and functional genomics studies in sorghum.

54 ENVIRONMENTAL SCIENCES↗

Data for Rapid and Efficient in planta Genome Editing in Sorghum Using Foxtail Mosaic Virus-mediated sgRNA Delivery

The requirement of in vitro tissue culture for the delivery of gene editing reagents limits the application of gene editing to commercially relevant varieties of many crop species. To overcome this bottleneck, plant RNA viruses have been deployed as versatile tools for in planta delivery of recombinant RNA. Viral delivery of single-guide RNAs (sgRNAs) to transgenic plants that stably express CRISPR-associated (Cas) endonuclease has been successfully used for targeted mutagenesis in several dicotyledonous and few monocotyledonous plants. Progress with this approach in monocotyledonous plants is limited so far by the availability of effective viral vectors. We engineered a set of foxtail mosaic virus (FoMV) and barley stripe mosaic virus (BSMV) vectors to deliver the fluorescent protein AmCyan to track viral infection and movement in Sorghum bicolor . We further used these viruses to deliver and express sgRNAs to Cas9 and Green Fluorescent Protein (GFP) expressing transgenic sorghum lines, targeting Phytoene desaturase (PDS), Magnesium-chelatase subunit I (MgCh), 4-hydroxy-3-methylbut-2-enyl diphosphate reductase, orthologs of maize Lemon white1 (Lw1) or GFP. The recombinant BSMV did neither infect sorghum nor deliver or express AmCyan and sgRNAs. In contrast, the recombinant FoMV systemically spread throughout sorghum plants and induced somatic mutations with frequencies reaching up to 60%. This mutagenesis led to visible phenotypic changes, demonstrating the potential of FoMV for in planta gene editing and functional genomics studies in sorghum.

Feedstock Production↗

Biophotonics and Bone Biology

One of the more serious side effects of extended space flight is an accelerated bone loss. Rates of bone loss are highest in the weight-bearing bones of the hip and spine regions, and the average rate of bone loss as measured by bone mineral density measurements is around 1.2% per month for persons in a microgravity environment. It is well known that bone remodeling responds to mechanical forces. We are developing two-photon microscopy techniques to study bone tissue and bone cell cultures to better understand the fundamental response mechanism in bone remodeling. Osteoblast and osteoclast cell cultures are being studied, and the goal is to use molecular biology techniques in conjunction with Fluorescence Lifetime Imaging Microscopy (FLIM) to study the physiology of in-vitro cell cultures in response to various stimuli, such as fluid flow induced shear stress and mechanical stress. We have constructed a two-photon fluorescence microscope for these studies, and are currently incorporating FLIM detection. Current progress will be reviewed. This work is supported by the NASA John Glenn Biomedical Engineering Consortium.

Zimmerli, Gregory↗

STS-45 Space Shuttle mission report

The STS-45 Space Shuttle Program Mission Report contains a summary of the vehicle subsystem operations during the forty-sixth flight of the Space Shuttle Program and the eleventh flight of the Orbiter Vehicle Atlantis (OV-104). In addition to the Atlantis vehicle, the flight vehicle consisted of the following: an External Tank (ET) designated as ET-44 (LWT-37); three Space Shuttle main engines (SSME's), which were serial numbers 2024, 2012, and 2028 in positions 1, 2, and 3, respectively; and two Solid Rocket Boosters (SRB's) designated as BI-049. The lightweight redesigned Solid Rocket Motors (RSRM's) installed in each of the SRB's were designated as 360L021A for the left SRM and 360W021B for the right SRM. The primary objective of this mission was to successfully perform the planned operations of the Atmospheric Laboratory for Applications and Science-1 (ATLAS-1) and the Shuttle Solar Backscatter Ultraviolet Instrument (SSBUV) payloads. The secondary objectives were to successfully perform all operations necessary to support the requirements of the following: the Space Tissue Loss-01 (STL-01) experiment; the Radiation Monitoring Equipment-3 (RME-3) experiment; the Visual Function Tester-2 (VFT-2) experiment; the Cloud Logic to Optimize use of Defense System (CLOUDS-1A) experiment; the Shuttle Amateur Radio Experiment 2 (SAREX-2) Configuration B; the Investigation into Polymer Membranes Processing experiment; and the Get-Away Special (GAS) payload G-229. The Ultraviolet Plume Instrument (UVPI) was a payload of opportunity that required no special maneuvers. In addition to the primary and secondary objectives, the crew was tasked to perform as many as 10 Development Test Objectives (DTO'S) and 14 Detailed Supplementary Objectives (DSO's).

Fricke, Robert W.↗

Pulmonary Toxicity Studies of Lunar Dust in Rodents

NASA has been contemplating returning astronauts to the moon for long-duration habitation and research and using it as a stepping-stone to Mars. Other spacefaring nations are planning to send humans to the moon for the first time. The surface of the moon is covered by a layer of fine dust. Fine terrestrial dusts, if inhaled, are known to pose a health risk to humans. Some Apollo crews briefly exposed to moon dust that adhered to spacesuits and became airborne in the Lunar Module reported eye and throat irritation. The habitable area of any lunar landing vehicle or outpost would inevitably become contaminated with lunar dust. To assess the health risks of exposure of humans to airborne lunar dust, we evaluated the toxicity of Apollo 14 moon dust in animal lungs. Studies of the pulmonary toxicity of a dust are generally first done by intratracheal instillation (ITI) of aqueous suspensions of the test dust into the lungs of rodents. If a test dust is irritating or cytotoxic to the lungs, the alveolar macrophages, after phagocytizing the dust particles, will release cellular messengers to recruit white blood cells (WBCs) and to induce dilation of blood capillary walls to make them porous, allowing the WBCs to gain access to the alveolar space. The dilation of capillary walls also allows serum proteins and water entering the lung. Besides altering capillary integrity, a toxic dust can also directly kill the cells that come into contact with it or ingest it, after which the dead cells would release their contents, including lactate dehydrogenase (a common enzyme marker of cell death or tissue damage). In the treated animals, we lavaged the lungs 1 and 4 weeks after the dust instillation and measured the concentrations of these biomarkers of toxicity in the bronchioalveolar lavage fluids to determine the toxicity of the dust. To assess whether the inflammation and cellular injury observed in the biomarker study would lead to persistent or progressive histopathological changes, a similar study was conducted to microscopically examine rat lung tissue and the associated lymph nodes for lesions, including fibrosis, 1 or 3 months after the instillation. The results from this ITI study led us to select two concentrations (20 and 60 mg/cu m) for an inhalation study, in which rats were exposed to lunar dust 6 h daily for 4 weeks (5d/wk). Similar biochemical and histopathological assessments were carried out in these rats 1 day or 1, 4, or 13 weeks after the dust exposure. Rats exposed to lunar dust by ITI or inhalation showed effects indicating that the dust is moderately toxic. The data will be useful to establish safe exposure limits for astronauts working in a lunar habitat and also help engineers designing dust mitigation systems for lunar vehicles and habitats.

Lam, Chiu-Wing↗

Pooled PPIseq: Screening the SARS-CoV-2 and human interface with a scalable multiplexed protein-protein interaction assay platform

Protein-Protein Interactions (PPIs) are a key interface between virus and host, and these interactions are important to both viral reprogramming of the host and to host restriction of viral infection. In particular, viral-host PPI networks can be used to further our understanding of the molecular mechanisms of tissue specificity, host range, and virulence. At higher scales, viral-host PPI screening could also be used to screen for small-molecule antivirals that interfere with essential viral-host interactions, or to explore how the PPI networks between interacting viral and host genomes co-evolve. Current high-throughput PPI assays have screened entire viral-host PPI networks. However, these studies are time consuming, often require specialized equipment, and are difficult to further scale. Here, we develop methods that make larger-scale viral-host PPI screening more accessible. This approach combines the mDHFR split-tag reporter with the iSeq2 interaction-barcoding system to permit massively-multiplexed PPI quantification by simple pooled engineering of barcoded constructs, integration of these constructs into budding yeast, and fitness measurements by pooled cell competitions and barcode-sequencing. We applied this method to screen for PPIs between SARS-CoV-2 proteins and human proteins, screening in triplicate >180,000 ORF-ORF combinations represented by >1,000,000 barcoded lineages. Our results complement previous screens by identifying 74 putative PPIs, including interactions between ORF7A with the taste receptors TAS2R41 and TAS2R7, and between NSP4 with the transmembrane KDELR2 and KDELR3. We show that this PPI screening method is highly scalable, enabling larger studies aimed at generating a broad understanding of how viral effector proteins converge on cellular targets to effect replication.

60 APPLIED LIFE SCIENCES↗

Evaluation of two inoculation routes of an adenovirus-mediated viral protein inhibitor in a Crimean-Congo hemorrhagic fever mouse model

Crimean-Congo hemorrhagic fever virus (CCHFV) is a tick-borne nairovirus with a wide geographic spread that can cause severe and lethal disease. No specific medical countermeasures are approved to combat this illness. The CCHFV L protein contains an ovarian tumor (OTU) domain with a cysteine protease thought to modulate cellular immune responses by removing ubiquitin and ISG15 post-translational modifications from host and viral proteins. Viral deubiquitinases like CCHFV OTU are attractive drug targets, as blocking their activity may enhance cellular immune responses to infection, and potentially inhibit viral replication itself. We previously demonstrated that the engineered ubiquitin variant CC4 is a potent inhibitor of CCHFV replication in vitro. A major challenge of the therapeutic use of small protein inhibitors such as CC4 is their requirement for intracellular delivery, e.g., by viral vectors. In this study, we examined the feasibility of in vivo CC4 delivery by a replication-deficient recombinant adenovirus (Ad-CC4) in a lethal CCHFV mouse model. Since the liver is a primary target of CCHFV infection, we aimed to optimize delivery to this organ by comparing intravenous (tail vein) and intraperitoneal injection of Ad-CC4. While tail vein injection is a traditional route for adenovirus delivery, in our hands intraperitoneal injection resulted in higher and more widespread levels of adenovirus genome in tissues, including, as intended, the liver. However, despite promising in vitro results, neither route of in vivo CC4 treatment resulted in protection from a lethal CCHFV infection.

59 BASIC BIOLOGICAL SCIENCES↗

Expression of dehydroshikimate dehydratase in poplar induces transcriptional and metabolic changes in the phenylpropanoid pathway

Abstract Modification of lignin in feedstocks via genetic engineering aims to reduce biomass recalcitrance to facilitate efficient conversion processes. These improvements can be achieved by expressing exogenous enzymes that interfere with native biosynthetic pathways responsible for the production of the lignin precursors. In planta expression of a bacterial 3-dehydroshikimate dehydratase in poplar trees reduced lignin content and altered the monomer composition, which enabled higher yields of sugars after cell wall polysaccharide hydrolysis. Understanding how plants respond to such genetic modifications at the transcriptional and metabolic levels is needed to facilitate further improvement and field deployment. In this work, we acquired fundamental knowledge on lignin-modified poplar expressing 3-dehydroshikimate dehydratase using RNA-seq and metabolomics. The data clearly demonstrate that changes in gene expression and metabolite abundance can occur in a strict spatiotemporal fashion, revealing tissue-specific responses in the xylem, phloem, or periderm. In the poplar line that exhibited the strongest reduction in lignin, we found that 3% of the transcripts had altered expression levels and ~19% of the detected metabolites had differential abundance in the xylem from older stems. The changes affected predominantly the shikimate and phenylpropanoid pathways as well as secondary cell wall metabolism, and resulted in significant accumulation of hydroxybenzoates derived from protocatechuate and salicylate.

59 BASIC BIOLOGICAL SCIENCES↗

Center for Lignocellulose Structure and Formation (CLSF)

Lignocellulose is the carbon- and energy-rich material synthesized by plants when they make secondary cell walls, e.g. in woody tissues. Plants annually convert gigatons of atmospheric CO 2 into these complex and useful biomaterials that comprise over half of all biological carbon on Earth. This biological conversion helps to reduce atmospheric CO 2 that contributes to climate change while generating renewable plant cell walls that are used commercially on a massive scale in the paper, timber and textile industries. Recent technical developments open new possibilities for use of modified wood and cellulose fibers as large-scale alternatives to steel, plastics, and other nonrenewable materials with high carbon footprints and energy inputs, as well as for generation of biofuels and bio-hydrogen. Despite the utility of plant-based biomaterials, many physical and biological aspects of cell wall structure and formation remain obscure, and this limits the current scope for engineering these renewable resources for greater utility.

09 BIOMASS FUELS↗

Data for Mitochondrial ATP Generation is More Proteome Efficient than Glycolysis

Metabolic efficiency profoundly influences organismal fitness. Heterotrophs, from yeast to mammals, derive usable energy primarily through glycolysis and respiration. While respiration is more energy-efficient, some cells favor glycolysis even when oxygen is available (aerobic glycolysis, Warburg effect). A leading explanation is that glycolysis is more efficient in terms of ATP production per unit mass of protein (i.e. faster). Through quantitative flux analysis and proteomics, we find however that mitochondrial respiration is actually more proteome-efficient than aerobic glycolysis. This is shown across yeasts, T cells, cancer cells, and tissues and tumors in vivo. Instead of aerobic glycolysis being valuable for fast ATP production, it correlates with high glycolytic protein expression, which is valuable for hypoxic growth. Aerobic glycolytic yeasts do not excel at aerobic growth, but outgrow respiratory cells in oxygen limitation. Thus, aerobic glycolysis emerges from cells maintaining a proteome conducive to both aerobic and hypoxic growth.

Metabolomics↗

Water Ice and Life's Roots in Space

Nearly three decades ago as Voyager 2 spacecraft raced out of the Solar System. NASA engineers turned its camera arm around (at the request of the American astronomer Carl Sagan) to take a parting snapshot of Earth. Earth's image was a single pale blue pixel, its color caused by the Rayleigh scattering of sunlight in the water of our oceans. Earth is a water planet, and this is the color of life. No matter how far we travel on our planet, no matter how high or deep, if we find liquid water, we find some form of life that manages to survive there. And yet there is a cruel irony. Water in its solid crystalline form is hostile to life. Organisms can roost in geysers, wallow in brine and gulp down acid, but they cowered from ice. The rigid ordering of water molecules in ice crystals expels impurities and tears organic tissue beyond repair. In fact, about the only good thing you can say about ice is that it gets out of the way: Its low density ensures that it floats and leaves the water dwelling creatures in peace. Recent discoveries have caused us to rethink this basic premise. New lines of evidence both observational and experimental - suggest that prebiotic organic compounds are not only comfortable in, but in fact had their origin in a peculiar form of solid water ice that is ubiquitous in interstellar space, but completely absent from Earth. Only recently have we been able to create even submicroscopic quantities of this ice in terrestrial laboratories, yet it constitutes the most abundant form of water in the universe. Interstellar ice is a far cry from the ice we are so familiar with on Earth. This interstellar ice has no crystalline structure, and despite the fact that its temperature is a scant few degrees above absolute zero (where all molecular motion ceases), it is highly reactive and can flow like water when exposed to radiation. It is in fact this ice's similarity to liquid water that allows it to participate in the creation of the very first organic compounds.

Blake, David↗

Structural characterization of ligand binding and pH-specific enzymatic activity of mouse Acidic Mammalian Chitinase

Chitin is an abundant biopolymer and pathogen-associated molecular pattern that stimulates a host innate immune response. Mammals express chitin-binding and chitin-degrading proteins to remove chitin from the body. One of these proteins, Acidic Mammalian Chitinase (AMCase), is an enzyme known for its ability to function under acidic conditions in the stomach but is also active in tissues with more neutral pHs, such as the lung. Here, we used a combination of biochemical, structural, and computational modeling approaches to examine how the mouse homolog (mAMCase) can act in both acidic and neutral environments. We measured kinetic properties of mAMCase activity across a broad pH range, quantifying its unusual dual activity optima at pH 2 and 7. We also solved high-resolution crystal structures of mAMCase in complex with oligomeric GlcNAcn, the building block of chitin, where we identified extensive conformational ligand heterogeneity. Leveraging these data, we conducted molecular dynamics simulations that suggest how a key catalytic residue could be protonated via distinct mechanisms in each of the two environmental pH ranges. These results integrate structural, biochemical, and computational approaches to deliver a more complete understanding of the catalytic mechanism governing mAMCase activity at different pH. Engineering proteins with tunable pH optima may provide new opportunities to develop improved enzyme variants, including AMCase, for therapeutic purposes in chitin degradation.

59 BASIC BIOLOGICAL SCIENCES↗

Forearm muscle oxygenation decreases with low levels of voluntary contraction

The purpose of our investigation was to determine if the near infrared spectroscopy technique was sensitive to changes in tissue oxygenation at low levels of isometric contraction in the extensor carpi radialis brevis muscle. Nine subjects were seated with the right arm abducted to 45 degrees, elbow flexed to 85 degrees, forearm pronated 45 degrees, and wrist and forearm supported on an armrest throughout the protocol. Altered tissue oxygenation was measured noninvasively with near infrared spectroscopy. The near infrared spectroscopy probe was placed over the extensor carpi radialis brevis of the subject's right forearm and secured with an elastic wrap. After 1 minute of baseline measurements taken with the muscle relaxed, four different loads were applied just proximal to the metacarpophalangeal joint such that the subjects isometrically contracted the extensor carpi radialis brevis at 5, 10, 15, and 50% of the maximum voluntary contraction for 1 minute each. A 3-minute recovery period followed each level of contraction. At the end of the protocol, with the probe still in place, a value for ischemic tissue oxygenation was obtained for each subject. This value was considered the physiological zero and hence 0% tissue oxygenation. Mean tissue oxygenation (+/-SE) decreased from resting baseline (100% tissue oxygenation) to 89 +/- 4, 81 +/- 8, 78 +/- 8, and 47 +/- 8% at 5, 10, 15, and 50% of the maximum voluntary contraction, respectively. Tissue oxygenation levels at 10, 15, and 50% of the maximum voluntary contraction were significantly lower (p < 0.05) than the baseline value. Our results indicate that tissue oxygenation significantly decreases during brief, low levels of static muscle contraction and that near infrared spectroscopy is a sensitive technique for detecting deoxygenation noninvasively at low levels of forearm muscle contraction. Our findings have important implications in occupational medicine because oxygen depletion induced by low levels of muscle contraction may be directly linked to muscle fatigue.

NASA Center ARC↗

Carbon fiber study. A compilation of an intergovernmental committee study

Carbon fibers have opened a wealth of new structural engineering and consumer product opportunities. The potential benefits are higher strength, and lighter weight military and commercial products, which portend energy savings and increases safety. Unfortunately, these benefits are not realized without risk. Inadvertent fiber release, during manufacture or by destruction of the resin binder in fire, is the major hazard associated with composites. The carbon (or graphite) fibers are finer than human hair and if released into the air, they can be easily transported by winds or currents. In contact with electrical devices, they can create resistive loading, short circuits, and arcing, resulting in stoppages or destruction. Their health impact is not fully known and requires careful research and analysis before any firm conclusions can be reached; however, based upon current available information, they are primarily an irritant to the eyes and skin, like fiberglass, rather than carcinogenic or destructive to lung tissue. Major manufacturers are aware of the unique problems associated with these materials and have successfully applied controls to avoid the inplant problems.

Source record↗

Biomedical Simulation Models of Human Auditory Processes

Detailed acoustic engineering models that explore noise propagation mechanisms associated with noise attenuation and transmission paths created when using hearing protectors such as earplugs and headsets in high noise environments. Biomedical finite element (FE) models are developed based on volume Computed Tomography scan data which provides explicit external ear, ear canal, middle ear ossicular bones and cochlea geometry. Results from these studies have enabled a greater understanding of hearing protector to flesh dynamics as well as prioritizing noise propagation mechanisms. Prioritization of noise mechanisms can form an essential framework for exploration of new design principles and methods in both earplug and earcup applications. These models are currently being used in development of a novel hearing protection evaluation system that can provide experimentally correlated psychoacoustic noise attenuation. Moreover, these FE models can be used to simulate the effects of blast related impulse noise on human auditory mechanisms and brain tissue.

Bicak, Mehmet M. A.↗

Compilation and utilization of a sorghum transcriptome compendium for gene regulatory network analysis and crop trait engineering

Sorghum bicolor (Sorghum) is a drought and heat tolerant C4 grass crop used to produce grain, forage, biofuels, and other bioproducts. Genetic improvement of sorghum hybrid crops is aided by a large and diverse germplasm, sorghum's diploid inbreeding genetics, and a relatively small genome that has facilitated genomic research. Over the past 20 years, the sorghum research community characterized the cytogenetic and recombinant landscapes of sorghum's 10 chromosomes, sequenced and annotated the sorghum genome, and used that information to identify genes/alleles that modulate flowering time, plant height, seed shattering, and other important traits. More recently, >1000 RNA-seq transcriptome profiles were collected from 15 sorghum genotypes to help understand the genetic basis of variation in growth and development of sorghum stems, tillers, roots, and leaves, and the regulation of biosynthetic pathways that produce epicuticular wax, dhurrin, and RFOs, compounds that contribute to sorghum's resilience. Transcriptome studies were designed to identify differentially expressed genes that are co-expressed during development or in response to a treatment to enable construction of gene regulatory networks. Co-expression and network analysis identified transcription factors and their cognate binding sites in target gene promoters and signaling pathways that modulate gene regulatory networks providing gene editing targets for further trait optimization. RNA-seq data from >20 experiments targeting sorghum organs, tissues, cell types, developmental stages, and responses to environmental conditions (i.e., diel, day-length, shading, water-deficit, temperature) has been compiled in a sorghum transcriptome compendium. The goal of this resource paper is to describe compendium content, accessibility, and a compendium data analysis pipeline and to illustrate the types of information that can be derived from the compendium with a focus on the elucidation of gene regulatory networks useful for guiding the improvement of sorghum traits through gene editing.

RNA-seq↗

STS-53 Space Shuttle mission report

The STS-53 Space Shuttle Program Mission Report provides a summary of the Orbiter, External Tank (ET), Solid Rocket Booster/Redesigned Solid Rocket Motor (SRB/RSRM), and the Space Shuttle Main Engine (SSME) subsystems performance during the fifty-second flight of the Space Shuttle Program, and the fifteenth flight of the Orbiter vehicle Discovery (OV-103). In addition to the Orbiter, the flight vehicle consisted of an ET, which was designated as ET-49/LWT-42; three SSME's, which were serial numbers 2024, 2012, and 2017 in positions 1, 2, and 3, respectively; and two SRB's, which were designated BI-055. The lightweight RSRM's that were installed in each SRB were designated 360L028A for the left SRB, and 360L028B for the right SRB. The primary objective of this flight was to successfully deploy the Department of Defense 1 (DOD-1) payload. The secondary objectives of this flight were to perform the operations required by the Glow Experiment/Cryogenic Heat Pipe Experiment Payload (GCP); the Hand-Held, Earth-Oriented, Real-Time, Cooperative, User-Friendly, Location-Targeting and Environmental System (HERCULES); the Space Tissue Loss (STL); the Battlefield Laser Acquisition Sensor Test (BLAST); the Radiation Monitoring Equipment-III (RME-III); the Microcapsules in Space-1 (MIS-1); the Visual Function Tester-2 (VFT-2); the Cosmic Radiation Effects and Activation Monitor (CREAM); the Clouds Logic to Optimize Use of Defense Systems-1A (CLOUDS-1A); the Fluids Acquisition and Resupply Experiment (FARE); and the Orbital Debris Radar Calibration Spheres (ODERACS). In addition to presenting a summary of subsystem performance, this report also discusses each Orbiter, ET, SSME, SRB, and RSRM in-flight anomaly in the applicable section of the report. Listed in the discussion of each anomaly is the officially assigned tracking number as published by each Project Office in their respective Problem Tracking List. All times given in this report are in Greenwich mean time (G.m.t.) as well as mission elapsed time (MET).

Fricke, Robert W., Jr.↗

Engineered plants for the production of the antioxidants arbutin and gallate

The shikimate pathway is a crucial metabolic route for the biosynthesis of numerous valuable chemicals. In this study, we engineered the shikimate pathway in plants via expression of microbial enzymes to produce the two important antioxidants gallate and arbutin. The engineered pathways utilize the aromatics protocatechuate and 4-hydroxybenzoate as metabolic intermediates. Through transient expression in Nicotiana benthamiana leaves, we first identified biosynthetic routes for the production of gallate from either chorismate or 3-dehydroshikimate. Gallate production was then achieved in Arabidopsis using a genetic background that overproduces protocatechuate and via expression of a mutated version of the 4-hydroxybenzoate hydroxylase PobA from Pseudomonas sp. Arbutin production was obtained in Arabidopsis using a genetic background that overproduces 4-hydroxybenzoate and via expression of the monooxygenase MNX1 from Candida parapsilosis. The best Arabidopsis transgenic lines accumulated gallate and arbutin in the range of 0.25 and 0.93 dry weight % (dwt%), respectively. Using sorghum for large-scale in planta production, the titers of gallate and arbutin produced from the intermediate 4-hydroxybenzoate reached 0.58 dwt% and 0.50 dwt%, respectively, in mature transgenic plants, surpassing levels typically observed in plants that naturally produce these compounds. Gallate and arbutin were readily extracted from plant tissues using methanol solvent. Analysis of extractive-free biomass showed only trace amounts of gallate and its precursors 4-hydroxybenzoate and protocatechuate crosslinked to cell walls, suggesting that they mainly occur as soluble conjugated forms stored in the vacuole. This study presents alternative synthesis routes using plant hosts for the eco-friendly production of gallate and arbutin.

Antioxidant↗