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Results for “Plant Biology”

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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

A Systems Biology Approach to Identify Essential Epigenetic Regulators for Specific Biological Processes in Plants

Upon sensing developmental or environmental cues, epigenetic regulators transform the chromatin landscape of a network of genes to modulate their expression and dictate adequate cellular and organismal responses. Knowledge of the specific biological processes and genomic loci controlled by each epigenetic regulator will greatly advance our understanding of epigenetic regulation in plants. To facilitate hypothesis generation and testing in this domain, we present EpiNet, an extensive gene regulatory network (GRN) featuring epigenetic regulators. EpiNet was enabled by (i) curated knowledge of epigenetic regulators involved in DNA methylation, histone modification, chromatin remodeling, and siRNA pathways; and (ii) a machine-learning network inference approach powered by a wealth of public transcriptome datasets. We applied GENIE3, a machine-learning network inference approach, to mine public Arabidopsis transcriptomes and construct tissue-specific GRNs with both epigenetic regulators and transcription factors as predictors. The resultant GRNs, named EpiNet, can now be intersected with individual transcriptomic studies on biological processes of interest to identify the most influential epigenetic regulators, as well as predicted gene targets of the epigenetic regulators. We demonstrate the validity of this approach using case studies of shoot and root apical meristem development.

root apical meristem↗
NASA NTRS2015

Plant Leachate Nutrient Recovery with Biological, Thermal, and Photocatalytic Pretreatments

Plants are ideal for long term space travel: provide essential resources - oxygen, water, food; Water-soaked plants expel soluble nutrients in a leachate solution - toxins and wastes are also expelled and inhibit growth; biological, thermal, photocatalytic coupled with an acid digestion treatment will hopefully maximize recovery and remove wastes

Nutrient Recovery↗
DOE OSTI2023

A Suite of Constitutive Promoters for Tuning Gene Expression in Plants

The need for convenient tools to express transgenes over a large dynamic range is pervasive throughout plant synthetic biology; however, current efforts are largely limited by the heavy reliance on a small set of strong promoters, precluding more nuanced and refined engineering endeavors in planta . To address this technical gap, we characterize a suite of constitutive promoters that span a wide range of transcriptional levels and develop a GoldenGate-based plasmid toolkit named PCONS, optimized for versatile cloning and rapid testing of transgene expression at varying strengths. We demonstrate how easy access to a stepwise gradient of expression levels can be used for optimizing synthetic transcriptional systems and the production of small molecules in planta . We also systematically investigate the potential of using PCONS as an internal standard in plant biology experimental design, establishing the best practices for signal normalization in experiments. Although our library has primarily been developed for optimizing expression in N. benthamiana , we demonstrate the translatability of our promoters across distantly related species using a multiplexed reporter assay with barcoded transcripts. In conclusion, our findings showcase the advantages of the PCONS library as an invaluable toolkit for plant synthetic biology.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

The Elements of Life, Photosynthesis and Genomics

I am a Professor of Biochemistry, Biophysics and Structural Biology and Plant and Microbial Biology at the University of California in Berkeley. I was born and raised in India, emigrated to the United States to attend university, earning a B.S. in Molecular Biology and a Ph.D. in Biochemistry at the University of Wisconsin in Madison. Following post-doctoral studies with Lawrence Bogorad at Harvard University where I became interested in genetic control of trace element quotas, I joined the department of Chemistry and Biochemistry at UCLA. One of the first to appreciate essential trace metals as potential regulators of gene expression, I articulated the details of the nutritional Cu regulon in Chlamydomonas. In parallel, I used genetic approaches to discover the genes governing missing steps in tetrapyrrole metabolism, including the attachment of heme to apocytochromes in the thylakoid lumen and the factors catalyzing the formation of ring V in chlorophyll. After biochemistry and classical genetics, I embraced genomics, taking a leadership role on the Joint Genome Institute’s efforts on the Chlamydomonas genome and more recently, contributing to high quality assemblies of several genomes in the green algal radiation, and large transcriptomic and proteomic datasets — focusing on the diel metabolic cycle in synchronized cultures and acclimation to key environmental and nutritional stressors — that are well-used and appreciated by the community. Finally, a new venture in Berkeley is the promotion of Auxenochlorella protothecoides as the true “green yeast” and as a platform for engineering algae to produce useful bioproducts.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1986

The possible involvement of root-cap mucilage in gravitropism and calcium movement across root tips of Allium cepa L

Roots of Allium cepa L. grown in aerated water elongate rapidly, but are not graviresponsive. These roots (1) possess extensive columella tissues comprised of cells containing numerous sedimented amyloplasts, (2) lack mucilage on their tips, and (3) are characterized by a weakly polar movement of calcium (Ca) across their tips. Placing roots in humid air correlates positively with the (1) onset of gravicurvature, (2) appearance of mucilage on tips of the roots, and (3) onset of the ability to transport Ca polarly to the lower side of the root tip. Gravicurvature of roots previously submerged in aerated water is more rapid when roots are oriented vertically for 1-2 h in humid air prior to being oriented horizontally. The more rapid gravicurvature of these roots correlates positively with the accumulation of mucilage at the tips of roots during the time the roots are oriented vertically. Therefore, the onset of gravicurvature and the ability of roots to transport Ca to the lower sides of their tips correlate positively with the presence of mucilage at their tips. These results suggest that mucilage may be important for the transport of Ca across root caps.

NASA Discipline Number 40-10↗
NASA NTRS1988

A gradient of endogenous calcium forms in mucilage of graviresponding roots of Zea mays

Agar blocks that contacted the upper sides of tips of horizontally-oriented roots of Zea mays contain significantly less calcium (Ca) than blocks that contacted the lower sides of such roots. This gravity-induced gradient of Ca forms prior to the onset of gravicurvature, and does not form across tips of vertically-oriented roots or roots of agravitropic mutants. These results indicate that (1) Ca can be collected from mucilage of graviresponding roots, (2) gravity induces a downward movement of endogenous Ca in mucilage overlying the root tip, (3) this gravity-induced gradient of Ca does not form across tips of agravitropic roots, and (4) formation of a Ca gradient is not a consequence of gravicurvature. These results are consistent with gravity-induced movement of Ca being a trigger for subsequent redistribution of growth effectors (e.g. auxin) that induce differential growth and gravicurvature.

NASA Discipline Number 40-10↗
NASA NTRS1985

Correlations between polyamine ratios and growth patterns in seedling roots

The levels of putrescine, cadaverine, spermidine and spermine were determined in seedling roots of pea, tomato, millet and corn, as well as in corn coleoptiles and pea internodes. In all roots, putrescine content increased as elongation progressed, and the putrescine/spermine ratio closely paralleled the sigmoid growth curve up until the time of lateral root initiation. Spermidine and spermine were most abundant near the apices and declined progressively with increasing age of the cells. In the zone of differentiation of root hairs in pea roots, putrescine rose progressively with increasing age, while cadaverine declined. In both pea internodes and corn coleoptiles, the putrescine/spermidine ratio rises with increasing age and elongation. Thus, a block in the conversion of the diamine putrescine to the triamine spermidine may be an important step in the change from cell division to cell elongation.

Non-NASA Center↗
NASA NTRS1988

Enzymic synthesis of indole-3-acetyl-1-O-beta-d-glucose. II. Metabolic characteristics of the enzyme

The synthesis of indole-3-acetyl-1-O-beta-D-glucose from indole-3-acetic acid (IAA) and uridine diphosphoglucose (UDPG) has been shown to be a reversible reaction with the equilibrium away from ester formation and toward formation of IAA. The enzyme occurs primarily in the liquid endosperm of the corn kernel but some activity occurs in the embryo. It is relatively specific showing no glucose ester formation with oxindole-3-acetic acid or 7-hydroxy-oxindole-3-acetic acid, and low activity with phenylpropene acids, such as rho-coumaric acid. The enzyme is also specific for the nucleotide sugar showing no activity with UDPGalactose or UDPXylose. The enzyme is inhibited by inorganic pyrophosphate, by phosphate esters and by phospholipids, particularly phosphatidyl ethanolamine. The enzyme is inhibited by zeatin, by 2,4-dichlorophenoxy-acetic acid, by IAA-myo-inositol and IAA-glucan, but not by zeatin riboside, and only weakly by gibberellic acid, abscisic acid and kinetin. The reaction is slightly stimulated by both calcium and calmodulin and, in some cases, by thiol compounds. The role of this enzyme in the homeostatic control of indole-3-acetic acid levels in Zea mays is discussed.

Non-NASA Center↗
NASA NTRS1991

Graviresponsiveness of surgically altered primary roots of Zea mays

We examined the gravitropic responses of surgically altered primary roots of Zea mays to determine the route by which gravitropic inhibitors move from the root tip to the elongating zone. Horizontally oriented roots, from which a 1-mm-wide girdle of epidermis plus 2-10 layers of cortex were removed from the apex of the elongating zone, curve downward. However, curvature occurred only apical to the girdle. Filling the girdle with mucilage-like material transmits curvature beyond the girdle. Vertically oriented roots with a half-girdle' (i.e. the epidermis and 2-10 layers of the cortex removed from half of the circumference of the apex of the elongating zone) curve away from the girdle. Inserting the half-girdle at the base of the elongating zone induces curvature towards the girdle. Filling the half-circumference girdles with mucilage-like material reduced curvature significantly. Stripping the epidermis and outer 2-5 layers of cortex from the terminal 1.5 cm of one side of a primary root induces curvature towards the cut, irrespective of the root's orientation to gravity. This effect is not due to desiccation since treated roots submerged in water also curved towards their cut surface. Coating a root's cut surface with a mucilage-like substance minimizes curvature. These results suggest that the outer cell-layers of the root, especially the epidermis, play an important role in root gravicurvature, and the gravitropic signals emanating from the root tip can move apoplastically through mucilage.

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 OSTI2022

Plant GATA Factors: Their Biology, Phylogeny, and Phylogenomics

GATA factors are evolutionarily conserved transcription factors that are found in animals, fungi, and plants. Compared to that of animals, the size of the plant GATA family is increased. In angiosperms, four main GATA classes and seven structural subfamilies can be defined. In recent years, knowledge about the biological role and regulation of plant GATAs has substantially improved. Individual family members have been implicated in the regulation of photomorphogenic growth, chlorophyll biosynthesis, chloroplast development, photosynthesis, and stomata formation, as well as root, leaf, and flower development. In this review, we summarize the current knowledge of plant GATA factors. Using phylogenomic analysis, we trace the evolutionary origin of the GATA classes in the green lineage and examine their relationship to animal and fungal GATAs. Lastly, we speculate about a possible conservation of GATA-regulated functions across the animal, fungal, and plant kingdoms.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS2015

Nutrient Recovery of Plant Leachates Under Thermal, Biological, and Photocatalytic Pretreatments

Nutrient recovery has always been a problem for long distance and long-term space missions. To allow humans to man these missions, a steady source of oxygen, water, and food are necessary for survival beyond Earth's atmosphere. Plants are currently an area of interest since they are capable of providing all three resources for life sustainability. We are currently interested in nutrient recovery for future plant growth and simple aqueous leachate extractions can recover some of the nutrients. However, leaching plants also removes water-soluble organic plant wastes, which inhibits plant growth if not separated properly. To combat the issues with waste and maximize nutrient recovery, we are attempting to pre-treat the plant matter using biological, thermal, and photocatalytic methods before subjecting the solution with variable-strength acid digestion. For the biological method, the inoculums: mixed heterotrophic/nitrifying bioreactor effluent and Trichoderma vessei are used in an attempt to liberate more nutrients from the plant matter. For the thermal method, plants are subjected to varying temperatures at different retention times to determine nutrient recovery. Lastly, the photocatalytic method utilizes TiO (sub 2)'s oxidizing abilities under specific pHs and retention times to reduce organic wastes and improve nutrient gains. A final acid digestion serves to liberate nutrients even further in order to maximize recovery. So far, we have tested ideal acid digestion variables for practicality and performance in our experiments. We found that a low retention time of 10 minutes and a high acid concentration of 0.1 and 1 mole HCl were the most effective at nutrient recovery. For space travel purposes, 0.1 mole currently looks like a viable acid digestion to use since it is relatively effective and sustainable from a mass and energy balance if acid recovery can be performed on waste brines. Biological pretreatments do not look to be too effective and the thermal and photocatalytic methods may be preferred since they show a potential to recover more than 70 percent of the nutrients.

Photocatalytic↗
NASA NTRS1996

Random root movements in weightlessness

The dynamics of root growth was studied in weightlessness. In the absence of the gravitropic reference direction during weightlessness, root movements could be controlled by spontaneous growth processes, without any corrective growth induced by the gravitropic system. If truly random of nature, the bending behavior should follow so-called 'random walk' mathematics during weightlessness. Predictions from this hypothesis were critically tested. In a Spacelab ESA-experiment, denoted RANDOM and carried out during the IML-2 Shuttle flight in July 1994, the growth of garden cress (Lepidium sativum) roots was followed by time lapse photography at 1-h intervals. The growth pattern was recorded for about 20 h. Root growth was significantly smaller in weightlessness as compared to gravity (control) conditions. It was found that the roots performed spontaneous movements in weightlessness. The average direction of deviation of the plants consistently stayed equal to zero, despite these spontaneous movements. The average squared deviation increased linearly with time as predicted theoretically (but only for 8-10 h). Autocorrelation calculations showed that bendings of the roots, as determined from the 1-h photographs, were uncorrelated after about a 2-h interval. It is concluded that random processes play an important role in root growth. Predictions from a random walk hypothesis as to the growth dynamics could explain parts of the growth patterns recorded. This test of the hypothesis required microgravity conditions as provided for in a space experiment.

STS-65 Shuttle Project↗
DOE OSTI2023

In planta single-molecule imaging and holographic force spectroscopy to study real-time, multimodal turnover dynamics of polysaccharides and associated carbohydrate metabolites

Cellular production of polysaccharides from simple sugar molecules serves critical roles in a variety of metabolic processes essential to the survival of every living organism. In the context of photosynthetically fixed carbon, cell wall polysaccharides synthesis is particularly of interest for increased biomass accumulation for human food, animal feed, and bioenergy related applications. Despite a long history of research in plant cell biology, our understanding of in planta cell wall biosynthesis and its regulation is far from complete due to lack of a comprehensive microscopy toolkit that encompass the multiple spatial and temporal scales in which cell wall polysaccharides fibrils are synthesized and assembled into intricate cell wall networks. In this project, a multidisciplinary team of scientists from Rutgers University, Vanderbilt University, and Oak Ridge National Laboratory carried out innovative multimodal, multiscale microscopy studies of cell wall synthesis using single-molecule force-spectroscopy, super-resolution fluorescence microscopy, and in vivo live cell imaging. Our novel multimodal and holistic imaging approach revealed plant cell wall polysaccharides synthesis processes in unprecedented detail across multiple spatiotemporal scales, from a single-molecule to a single-cell. Besides, the team has made technical and scientific innovations across multiple research fields—microscopy, bioengineering, single-molecule biophysics, and plant biology, etc.—to accomplish the goals. The results from this project will greatly advance the mechanistic and holistic understanding of in planta cell wall synthesis, which will accelerate the development of better transgenic crops for bioenergy applications. Moreover, the new toolbox, combining powerful advanced microscopy assays with cell/protein engineering, will have broader impacts on molecular and cellular biology fields by paving the way for studying cellular processes occurring across multiple physical scales with multimodal microscopy methodologies.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1988

Asymmetric distribution of glucose and indole-3-acetyl-myo-inositol in geostimulated Zea mays seedlings

Indole-3-acetyl-myo-inositol occurs in both the kernel and vegetative shoot of germinating Zea mays seedlings. The effect of a gravitational stimulus on the transport of [3H]-5-indole-3-acetyl-myo-inositol and [U-14C]-D-glucose from the kernel to the seedling shoot was studied. Both labeled glucose and labeled indole-3-acetyl-myo-inositol become asymmetrically distributed in the mesocotyl cortex of the shoot with more radioactivity occurring in the bottom half of a horizontally placed seedling. Asymmetric distribution of [3H]indole-3-acetic acid, derived from the applied [3H]indole-3-acetyl-myo-inositol, occurred more rapidly than distribution of total 3H-radioactivity. These findings demonstrate that the gravitational stimulus can induce an asymmetric distribution of substances being transported from kernel to shoot. They also indicate that, in addition to the transport asymmetry, gravity affects the steady state amount of indole-3-acetic acid derived from indole-3-acetyl-myo-inositol.

NASA Discipline Number 40-10↗
NASA NTRS1992

Effect of calmodulin antagonists on the growth and graviresponsiveness of primary roots of maize

We examined the effect of calmodulin (CaM) antagonists applied at the root tip on root growth, gravity-induced root curvature, and the movement of calcium across the root tip and auxin (IAA) across the elongation zone of gravistimulated roots. All of the CaM antagonists used in these studies delayed gravity-induced curvature at a concentration (1 micromole) that did not affect root growth. Calmodulin antagonists (> or = 1 micromole) inhibited downward transport of label from 45Ca2+ across the caps of gravistimulated roots relative to the downward transport of 45Ca2+ in gravistimulated roots which were not treated with CaM antagonists. Application of CaM antagonists at the root tip (> or = 1 micromole) also decreased the relative downward movement of label from 3H-IAA applied to the upper side of the elongation zone of gravistimulated roots. In general, tip application of antagonists inhibited neither the upward transport of 45Ca2+ in the root tip nor the upward movement of label from 3H-IAA in the elongation zone of gravistimulated roots. Thus, roots treated with CaM antagonists > or = 1 micromole become less graviresponsive and exhibit reduced or even a reversal of downward polarity of calcium transport across the root tip and IAA transport across the elongation zone. The results indicate that calmodulin-regulated events play a role in root gravitropism.

NASA Discipline Plant Biology↗