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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Variation in Biomass Yield and Cell Wall Composition in Switchgrass Natural Variants Under Two Nitrogen Regimes

Switchgrass (Panicum virgatum) is a promising lignocellulosic biofuel crop for which biomass and processing quality are important. Inherent plant variability across genotypes and environments challenges uniformity and product quality. In this study, the impact of nitrogen (N) application on switchgrass yield and quality was examined under field conditions using a highly diverse switchgrass panel over a 4-year period at Knoxville, TN. Overall, biomass production was correlated between low (0 kg of added N/ha) and moderate (135 kg of added N/ha) nitrogen treatments, suggesting that the N impact is largely uniform across the genotypes. Nonetheless, high biomass genotypes were identified with high nitrogen-use efficiency ; biomass was congruent or even higher (up to 9-fold) in the low N treatment. Genotypes were also identified with up to 94% nitrogen-remobilization efficiency. Furthermore, nitrogen application appeared to impact lignin content in whole tillers but was neutral to lignin monomer syringyl-to-guaiacyl (S/G) ratio. The same panel grown under natural conditions in Watkinsville, GA, produced significantly more biomass than the Tennessee panel in the first 3 years, but biomass was similar across both sites and treatments in year 4. Top performing genotypes overlapped between sites by 20-37%. There were low correlations in lignin content in whole tillers across the two field sites, but moderate correlations were observed for S/G ratios. The high yielding genotypes from the low N plot identified in this study can be used in breeding programs and management strategies in switchgrass to evade adverse environmental and economic effects.

09 BIOMASS FUELS↗
DOE OSTI2020

The AGCVIII kinase Dw2 modulates cell proliferation, endomembrane trafficking, and MLG/xylan cell wall localization in elongating stem internodes of Sorghum bicolor

Stems of bioenergy sorghum (Sorghum bicolor L. Moench.), a drought–tolerant C4 grass, contain up to 50 nodes and internodes of varying length that span 4–5 m and account for approximately 84% of harvested biomass. Stem internode growth impacts plant height and biomass accumulation and is regulated by brassinosteroid signaling, auxin transport, and gibberellin biosynthesis. In addition, an AGCVIII kinase (Dw2) regulates sorghum stem internode growth, but the underlying mechanism and signaling network are unknown. Here we provide evidence that mutation of Dw2 reduces cell proliferation in internode intercalary meristems, inhibits endocytosis, and alters the distribution of heteroxylan and mixed linkage glucan in cell walls. Phosphoproteomic analysis showed that Dw2 signaling influences the phosphorylation of proteins involved in lipid signaling (PLDδ), endomembrane trafficking, hormone, light, and receptor signaling, and photosynthesis. Altogether, our results show that Dw2 modulates endomembrane function and cell division during sorghum internode growth, providing insight into the regulation of monocot stem development.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1990

The role of wall calcium in the extension of cell walls of soybean hypocotyls

Calcium crosslinks are load-bearing bonds in soybean (Glycine max (L.) Merr.) hypocotyl cell walls, but they are not the same load-bearing bonds that are broken during acid-mediated cell elongation. This conclusion is reached by studying the relationship between wall calcium, pH and the facilitated creep of frozen-thawed soybean hypocotyl sections. Supporting data include the following observations: 1) 2-[(2-bis-[carboxymethyl]amino-5-methylphenoxy)methyl]-6-methoxy-8-bis[car boxymethyl]aminoquinoline (Quin 2) and ethylene glycol-bis(2-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) caused only limited facilitated creep as compared with acid, despite removal of comparable or larger amounts of wall calcium; 2) the pH-response curves for calcium removal and acid-facilitated creep were different; 3) reversible acid-extension occurred even after removal of almost all wall calcium with Quin 2; and 4) growth of abraded sections did not involve a proportional loss of wall calcium. Removal of wall calcium, however, increased the capacity of the walls to undergo acid-facilitated creep. These data indicate that breakage of calcium crosslinks is not a major mechanism of cell-wall loosening in soybean hypocotyl tissues.

Non-NASA Center↗
NASA NTRS1987

Wall relaxation and the driving forces for cell expansive growth

When water uptake by growing cells is prevented, the turgor pressure and the tensile stress in the cell wall are reduced by continued wall loosening. This process, termed in vivo stress relaxation, provides a new way to study the dynamics of wall loosening and to measure the wall yield threshold and the physiological wall extensibility. Stress relaxation experiments indicate that wall stress supplies the mechanical driving force for wall yielding. Cell expansion also requires water absorption. The driving force for water uptake during growth is created by wall relaxation, which lowers the water potential of the expanding cells. New techniques for measuring this driving force show that it is smaller than believed previously; in elongating stems it is only 0.3 to 0.5 bar. This means that the hydraulic resistance of the water transport pathway is small and that rate of cell expansion is controlled primarily by wall loosening and yielding.

NASA Program Space Biology↗
DOE OSTI2021

Multiscale Catalytic Fast Pyrolysis of Grindelia Reveals Opportunities for Generating Low Oxygen Content Bio-Oils from Drought Tolerant Biomass

Grindelia squarrosa (curlycup gumweed) biomass possesses unique biochemistry, cell wall composition, and leaf architecture tailored for prolific growth in arid and semiarid climates. Most notably, this plant has developed high levels of extractable resins that have high effective H/C eff ratios ((mol H - 2 x mol O)/mol C), which is hypothesized to lead to low coke formation during catalytic fast pyrolysis (CFP) over the ZSM-5 catalyst. In microscale experiments with high ZSM-5 loadings (biomass-to-catalyst mass ratio (B/C) ~ 0.1), in situ CFP generated high yields of aromatic hydrocarbons (30% carbon yield) while ex situ CFP favored aliphatic hydrocarbons (25% carbon yield). The difference between the two configurations was attributed to the constant catalyst temperature during ex situ CFP. Deactivation leading to partially deoxygenated vapor products occurred rapidly until B/C ≤ 0.5 by the adsorption of organic species blocking access to acid sites inside the micropores of the catalyst. This was followed by more gradual deactivation leading to primary vapor breakthrough, which we attribute to coke formation on acid sites on the external surface of ZSM-5 crystallites. Noncatalytic fast pyrolysis of Grindelia in a bench scale reactor produced oils with oxygen content (18 wt % on dry basis) and carbon yield (33%) comparable to those of CFP of woody biomass. The CFP of Grindelia further reduced the oxygen content to 7 wt % for in situ CFP and 4 wt % for ex situ CFP at B/C of 2-3. The good deoxygenation was attributed to a combination of a high H/C eff ratio and overall better quality of the pyrolysis vapors that were passed over the ZSM-5 catalyst. The high inorganic content of the Grindelia likely catalyzed pyrolysis to remove oxygenated coke precursors. This integrated CFP study demonstrated that Grindelia could be an important feedstock for generating stabilized noncatalytic and CFP oils for downstream processing into fuels and/or extraction of high-value chemicals. The preprocessing of this feedstock will be required to remove inorganics, which cause an irreversible deactivation of ZSM-5.

BIOMASS FUELS↗
NASA NTRS1997

Plant responses to environmental stress: regulation and functions of the Arabidopsis TCH genes

Expression of the Arabidopsis TCH genes is markedly upregulated in response to a variety of environmental stimuli including the seemingly innocuous stimulus of touch. Understanding the mechanism(s) and factors that control TCH gene regulation will shed light on the signaling pathways that enable plants to respond to environmental conditions. The TCH proteins include calmodulin, calmodulin-related proteins and a xyloglucan endotransglycosylase. Expression analyses and localization of protein accumulation indicates that the potential sites of TCH protein function include expanding cells and tissues under mechanical strain. We hypothesize that at least a subset of the TCH proteins may collaborate in cell wall biogenesis.

Review, Tutorial↗
DOE OSTI2025

An overview of switchgrass phenotypes variability across diverse populations and their implications for conversion to fuels

There have been substantial changes to the human lifestyle over the past two centuries, which are reflected in the amount of fuel we consume to power our day-to-day needs. The way we use these resources has indeed manifested in an overdependence on non-renewable energy sources, such as coal and petroleum, for generating electricity and powering our transportation needs. There is a pressing need to explore alternative ways of fueling our current lifestyle without impacting the environment. Biofuels have long been touted as a sustainable solution for use as drop-in fuels in aviation and maritime applications. Still, they have yet to establish themselves as a competitive commercial alternative, necessitating further research and development. Lignocellulosic biomass is an underutilized resource that is widely accessible for the commercial processing of renewable biofuels. Bioenergy crops, such as switchgrass (Panicum virgatum L.), which can be cultivated on marginal lands with minimal competition for agricultural land, are an ideal and promising candidate for bulk-scale biofuel synthesis. Over the past 30 years, significant progress has been made in breeding and genetically modifying these grasses to enhance their drought resilience and subsequent yields. However, discrepancies in biomass composition can lead to irregular feedstocks for downstream operations, which in turn affect overall production targets for biofuels. Here, this review examines the variability in switchgrass (P. virgatum L.) biomass phenotypes across diverse populations and plant components, and their implications for biofuel conversion. The study highlights significant variations in biomass yield, composition, and cell wall chemistry both between switchgrass genotypes and within individual cultivars. Key findings include differences in cellulose, hemicellulose, and lignin content between leaves and stems, which affect biomass digestibility and ethanol yield. The review also discusses the impact of lignin chemistry, particularly the syringyl/guaicyl (S/G) ratio, on the efficiency of biomass saccharification. Furthermore, it explores how these variations respond differently to various pretreatment techniques, affecting overall biofuel production. We conclude that understanding and quantifying this variability is crucial for optimizing switchgrass as a feedstock for commercial biofuel production, thereby potentially addressing the pressing need for sustainable energy sources in sectors such as aviation.

Kousika, Rohit [Univ. of Tennessee, Knoxville, TN ↗
DOE OSTI2025

Engineering 2‐Pyrone‐4,6‐Dicarboxylic Acid Production Reveals Metabolic Plasticity of Poplar

Woody biomass is a promising source of fermentable sugars for biofuels and bio-based chemicals, but its industrial use is limited by the costly biorefinery process. A viable strategy to reduce costs involves enhancing both biomass processability and the generation of high-value co-products. Here, we report the implementation of a synthetic metabolic pathway in Populus tremula × P. alba to produce 2-pyrone-4,6-dicarboxylic acid (PDC), a key building block for biodegradable plastics and high-performance materials. This artificial pathway—comprising microbial genes AroG, QsuB, PmdA, PmdB, and PmdC—enabled de novo PDC production in the stems of transgenic poplar. Pathway expression also induced substantial metabolic reprogramming and altered cell wall composition. These include the hyperaccumulation of simple phenolics like protocatechuic acid (PCA) and vanillic acid (VA), alongside reduced levels of p-hydroxybenzoic acid. A large portion of VA was ester-linked to cell wall lignin, while PCA was incorporated into the lignin backbone, forming novel benzodioxane units; concurrently, lignin in transgenic plants exhibited a drastic reduction in guaiacyl- and syringyl-units, with a notable increase in p-hydroxyphenyl-units. Hemicellulose content, particularly xylan, was also significantly increased. Moreover, expression of the PDC-pathway led to the formation of novel VA-derived suberin aromatics, enhancing suberization in bark and roots and improving salt stress tolerance. These changes led to improved saccharification efficiency, with up to 25% more glucose and 2.5 times xylose released from woody biomass. These results demonstrate the metabolic flexibility of poplar and highlight its potential for engineering cost-effective, stress-resilient bioenergy crops with enhanced biorefinery traits.

2-pyrone-4↗
DOE OSTI2026

Engineered Production of Hydroxycinnamoyl Tyramine Conjugates Limits the Growth of the Pathogen Pseudomonas syringae in Arabidopsis

Hydroxycinnamoyl tyramine conjugates are phenolamides produced by plants in response to pathogen attack and biotic stresses. Their proposed mechanisms of action include cytotoxicity towards pathogens, cell wall reinforcement to restrict pathogen proliferation, and signaling activity to trigger general stress responses. Here, we engineered the production of the tyramine conjugates p-coumaroyltyramine (CT) and feruloyltyramine (FT) in Arabidopsis to gain insight into their mode of action. Co-expression of feedback-insensitive 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase and tyrosine decarboxylase increased tyramine content. Additional expression of tyramine hydroxycinnamoyltransferase led to de-novo production of CT and FT, which were found as soluble and cell-wall-bound forms. FT was associated with lignin in stems. The growth of pathogenic Pseudomonas syringae was reduced in rosettes of the Arabidopsis CT- and FT-producing lines compared to wild type. These lines also exhibited increased transpirational water loss in excised rosettes. Transcriptomic analysis of transgenic lines grown under normal conditions revealed alterations in the expression of genes associated with the biological circadian clock. These changes led to a reduction in flavonoids and an early flowering phenotype. Important changes in the expression of genes related to abiotic stress such as drought, cold, heat, and hypoxia potentially contribute to reduced growth of P. syringae in engineered Arabidopsis.

Phenolamides↗
NASA NTRS1989

Calcium bridges are not load-bearing cell-wall bonds in Avena coleoptiles

I examined the ability of frozen-thawed Avena sativa L. coleoptile sections under applied load to extend in response to the calcium chelators ethyleneglycol-bis-(beta-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA) and 2-[(2-bis-[carboxymethyl]amino-5-methylphenoxy)methyl]-6-methoxy-8-bis[car boxymethyl]aminoquinoline (Quin II). Addition of 5 mM EGTA to weakly buffered (0.1 mM, pH 6.2) solutions of 2(N-morpholino) ethanesulfonic acid (Mes) initiated rapid extension and wall acidification. When the buffer strength was increased (e.g. from 20 to 100 mM Mes, pH 6.2) EGTA did not initiate extension nor did it cause wall acidification. At 5 mM Quin II failed to stimulate cell extension or wall acidification at all buffer molarities tested (0.1 to 100 mM Mes). Both chelators rapidly and effectively removed Ca2+ from Avena sections. These data indicate that Ca2+ chelation per se does not result in loosening of Avena cells walls. Rather, EGTA promotes wall extension indirectly via wall acidification.

NASA Program Space Biology↗
DOE OSTI2023

Systematic approaches to C-lignin engineering in Medicago truncatula

Abstract Background C-lignin is a homopolymer of caffeyl alcohol present in the seed coats of a variety of plant species including vanilla orchid, various cacti, and the ornamental plant Cleome hassleriana . Because of its unique chemical and physical properties, there is considerable interest in engineering C-lignin into the cell walls of bioenergy crops as a high-value co-product of bioprocessing. We have used information from a transcriptomic analysis of developing C. hassleriana seed coats to suggest strategies for engineering C-lignin in a heterologous system, using hairy roots of the model legume Medicago truncatula . Results We systematically tested strategies for C-lignin engineering using a combination of gene overexpression and RNAi-mediated knockdown in the caffeic acid/5-hydroxy coniferaldehyde 3/5-O-methyltransferase ( comt ) mutant background, monitoring the outcomes by analysis of lignin composition and profiling of monolignol pathway metabolites. In all cases, C-lignin accumulation required strong down-regulation of caffeoyl CoA 3- O -methyltransferase (CCoAOMT) paired with loss of function of COMT. Overexpression of the Selaginella moellendorffii ferulate 5-hydroxylase ( SmF5H ) gene in comt mutant hairy roots resulted in lines that unexpectedly accumulated high levels of S-lignin. Conclusion C-Lignin accumulation of up to 15% of total lignin in lines with the greatest reduction in CCoAOMT expression required the strong down-regulation of both COMT and CCoAOMT, but did not require expression of a heterologous laccase, cinnamyl alcohol dehydrogenase (CAD) or cinnamoyl CoA reductase (CCR) with preference for 3,4-dihydroxy-substituted substrates in M. truncatula hairy roots. Cell wall fractionation studies suggested that the engineered C-units are not present in a heteropolymer with the bulk of the G-lignin.

09 BIOMASS FUELS↗
NASA NTRS1999

Gravisensing, apoptosis, and drug recovery in Taxus cell suspensions

Haploid and diploid cell suspensions of Taxus spp. were examined for their adaptive plasticity in response to simulated microgravity, unit gravity, and hypergravity. Cell suspensions produced the taxane, paclitaxel, (TAXOL (R)), which is useful for the treatment of various cancers. Amyloplasts contributed to taxane ring biosynthesis and to drug release at the cell wall. Drug-producing cells reacted as gravisensing osmotic tensiometers. In stressed cells, amyloplasts docked and fused in clusters to sites on the plasmalemma before taxane discharge into the culture medium. In simulated microgravity and compared to all other treatments, taxane production was reduced nearly 100-fold. The percent paclitaxel of total taxanes remained 3-to 6-fold greater, and biomass doubled. When p53-independent programmed cell death was induced, taxanes were released into the culture medium as free molecules (soluble and insoluble) or bound to membranes, nuclear fragments, xylan residues, and other particulate materials. Unit gravity and especially hypergravity promoted xylogenesis and significant drug overproduction. A model relating families of >touch = (TCH), taxane early response (TER), nuclear cycling, and apoptosis-regulating genes to gravisensing, cell wall modifications, and to taxane recovery accounted for most but not all of the observations.

Paclitaxel/biosynthesis↗
NASA NTRS1988

Production and characterization of monoclonal antibodies to wall-localized peroxidases from corn seedlings

A library of 22 hybridomas, which make antibodies to soluble wall antigens from the coleoptiles and primary leaves of etiolated corn (Zea mays L.) seedlings, was raised and cloned three times by limit dilution to assure monoclonal growth and stability. Two of these hybridomas made immunoglobulin G antibodies, designated mWP3 and mWP19, which both effectively immunoprecipitated peroxidase activity from crude and partially purified preparations of wall peroxidases. Direct peroxidase-binding assays revealed that both antibodies bound enzymes with peroxidase activity. As judged by immunoblot analyses, mWP3 recognized a Mr 98,000 wall peroxidase with an isoelectric point near 4.2, and mWP19 recognized a Mr 58,000 wall peroxidase. Immunogold localization studies showed both peroxidases are predominately in cell walls.

NASA Discipline Number 40-10↗
DOE OSTI2023

Jasmonate activates secondary cell wall biosynthesis through MYC2–MYB46 module

Formation of secondary cell wall (SCW) is tightly regulated spatiotemporally by various developmental and environmental signals. Successful fine-tuning of the trade-off between SCW biosynthesis and stress responses requires a better understanding of how plant growth is regulated under environmental stress conditions. However, the current understanding of the interplay between environmental signaling and SCW formation is limited. The lipid-derived plant hormone jasmonate (JA) and its derivatives are important signaling components involved in various physiological processes including plant growth, development, and abiotic/biotic stress responses. Recent studies suggest that JA is involved in SCW formation but the signaling pathway has not been studied for how JA regulates SCW formation. We tested this hypothesis using the transcription factor MYB46, a master switch for SCW biosynthesis, and JA treatments. Both the transcript and protein levels of MYB46, a master switch for SCW formation, were significantly increased by JA treatment, resulting in the upregulation of SCW biosynthesis. We then show that this JA-induced upregulation of MYB46 is mediated by MYC2, a central regulator of JA signaling, which binds to the promoter of MYB46. We conclude that this MYC2-MYB46 module is a key component of the plant response to JA in SCW formation.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1998

The macromolecular aromatic domain in suberized tissue: a changing paradigm

As a structural feature of specialized cell walls, suberization remains an enigma, despite its obvious importance both during normal growth and development and as a stress response in plants. While it is clear that suberized tissues contain both polyaromatic and polyaliphatic domains, and that each of these has its own unique characteristics, whether there is a contiguous macromolecule that can be called suberin is an open question. From a structural perspective, the aromatic domain is unique and distinct from lignin, and is apparently comprised primarily of (poly)hydroxycinnamates, such as amides (e.g., feruloyltyramine). The aliphatic domain is also unique, being quite distinct from cutin in terms of both its chemical composition and cellular location. In the present paper, histochemical, structural and biochemical data, particularly, regarding the polyaromatic domain of suberized tissues, are critically reviewed. A revised description of the polyaromatic domain of suberized tissues, based on the consensus that is emerging from the current data, is presented and especially includes a spatially distinct (poly)hydroxycinnamoyl-containing macromolecule.

Non-NASA Center↗
NASA NTRS1996

Cytochemical localization of reserves during seed development in Arabidopsis thaliana under spaceflight conditions

Successful development of seeds under spaceflight conditions has been an elusive goal of numerous long-duration experiments with plants on orbital spacecraft. Because carbohydrate metabolism undergoes changes when plants are grown in microgravity, developing seed storage reserves might be detrimentally affected during spaceflight. Seed development in Arabidopsis thaliana plants that flowered during 11 d in space on shuttle mission STS-68 has been investigated in this study. Plants were grown to the rosette stage (13 d) on a nutrient agar medium on the ground and loaded into the Plant Growth Unit flight hardware 18 h prior to lift-off. Plants were retrieved 3 h after landing and siliques were immediately removed from plants. Young seeds were fixed and processed for microscopic observation. Seeds in both the ground control and flight plants are similar in their morphology and size. The oldest seeds from these plants contain completely developed embryos and seed coats. These embryos developed radicle, hypocotyl, meristematic apical tissue, and differentiated cotyledons. Protoderm, procambium, and primary ground tissue had differentiated. Reserves such as starch and protein were deposited in the embryos during tissue differentiation. The aleurone layer contains a large quantity of storage protein and starch grains. A seed coat developed from integuments of the ovule with gradual change in cell composition and cell material deposition. Carbohydrates were deposited in outer integument cells especially in the outside cell walls. Starch grains decreased in number per cell in the integument during seed coat development. All these characteristics during seed development represent normal features in the ground control plants and show that the spaceflight environment does not prevent normal development of seeds in Arabidopsis.

STS-68 Shuttle Project↗
NASA NTRS1996

Life in a changing world: TCH gene regulation of expression and responses to environmental signals

The Arabidopsis TCH genes were discovered as a consequence of their marked upregulation of expression in response to seemingly innocuous stimuli such as touch. Further analyses have indicated that these genes are upregulated by a variety of diverse stimuli. Understanding the mechanism(s) and factors that control TCH gene regulation will shed light on the signaling pathways that enable plants to respond to changing environmental conditions. The TCH proteins include calmodulin, calmodulin-related proteins and a xyloglucan endotransglycosylase. Expression analyses and localization of protein accumulation indicate that the potential sites of TCH protein function include expanding cells and tissues under mechanical strain. We hypothesize that the TCH proteins may collaborate in cell wall biogenesis.

NASA Discipline Plant Biology↗