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Research Containing: Seedling

Space, the final frontier: A critical review of recent experiments performed in microgravity

by on 22 August 2016in Biology & Biotechnology No comment

Space biology provides an opportunity to study plant physiology and development in a unique microgravity environment. Recent space studies with plants have provided interesting insights into plant biology, including discovering that plants can grow seed-to-seed in microgravity, as well as identifying novel responses to light. However, spaceflight experiments are not without their challenges, including limited space, limited access, and stressors such as lack of convection and cosmic radiation. Therefore, it is important to design experiments in a way to maximize the scientific return from research conducted on orbiting platforms such as the International Space Station. Here, we provide a critical review of recent spaceflight experiments and suggest ways in which future experiments can be designed to improve the value and applicability of the results generated. These potential improvements include: utilizing in-flight controls to delineate microgravity versus other spaceflight effects, increasing scientific return via next-generation sequencing technologies, and utilizing multiple genotypes to ensure results are not unique to one genetic background. Space experiments have given us new insights into plant biology. However, to move forward, special care should be given to maximize science return in understanding both microgravity itself as well as the combinatorial effects of living in space.

Related URLs:
http://www.ncbi.nlm.nih.gov/pubmed/26795156

Suppression of Hydroxycinnamate Network Formation in Cell Walls of Rice Shoots Grown under Microgravity Conditions in Space

by on 22 August 2016in Biology & Biotechnology No comment

Network structures created by hydroxycinnamate cross-links within the cell wall architecture of gramineous plants make the cell wall resistant to the gravitational force of the earth. In this study, the effects of microgravity on the formation of cell wall-bound hydroxycinnamates were examined using etiolated rice shoots simultaneously grown under artificial 1 g and microgravity conditions in the Cell Biology Experiment Facility on the International Space Station. Measurement of the mechanical properties of cell walls showed that shoot cell walls became stiff during the growth period and that microgravity suppressed this stiffening. Amounts of cell wall polysaccharides, cell wall-bound phenolic acids, and lignin in rice shoots increased as the shoot grew. Microgravity did not influence changes in the amounts of cell wall polysaccharides or phenolic acid monomers such as ferulic acid (FA) and p-coumaric acid, but it suppressed increases in diferulic acid (DFA) isomers and lignin. Activities of the enzymes phenylalanine ammonia-lyase (PAL) and cell wall-bound peroxidase (CW-PRX) in shoots also increased as the shoot grew. PAL activity in microgravity-grown shoots was almost comparable to that in artificial 1 g-grown shoots, while CW-PRX activity increased less in microgravity-grown shoots than in artificial 1 g-grown shoots. Furthermore, the increases in expression levels of some class III peroxidase genes were reduced under microgravity conditions. These results suggest that a microgravity environment modifies the expression levels of certain class III peroxidase genes in rice shoots, that the resultant reduction of CW-PRX activity may be involved in suppressing DFA formation and lignin polymerization, and that this suppression may cause a decrease in cross-linkages within the cell wall architecture. The reduction in intra-network structures may contribute to keeping the cell wall loose under microgravity conditions.

Related URLs:
http://www.ncbi.nlm.nih.gov/pubmed/26378793

New Insights in Plant Biology Gained from Research in Space

by on 22 August 2016in Biology & Biotechnology No comment

Recent space flight experiments have provided many new insights into the role of gravity in plant growth and development. Scientists have been taking seeds and plants into space for decades in an effort to understand how the stressful environment of space affects them. The resultant data have yielded significant advances in the development of advanced life-support systems for long-duration space flight and a better understanding of the fundamental role of gravity in directing the growth and development of plants. Experiments have improved as new spaceflight hardware and technology paved the way for progressively more insightful and rigorous plant research in space. The International Space Station (ISS) provided an opportunity for scientists to both monitor and control their experiments in real-time. Experiments on the ISS have provided valuable insights into endogenous growth responses, light-responses, and transcriptomic and proteomic changes that occur in the microgravity environment. In recent years most studies of plants in space have used Arabidopsis thaliana, but the single-celled, Ceratopteris richardii spore is also a valuable model system that has been used to understand plant gravity response. Experiments using these fern spores have revealed a dynamic and gravity-responsive trans-cell Ca2+ current that directs polarization of these spores, and a possible role of extracellular nucleotides in establishing or contributing to this current. As technology continues to improve, space flight experiments will provide many new insights into the role and effects of gravity on plant growth and development.

Related URLs:
http://gravitationalandspacebiology.org/index.php/journal/article/view/692

The actin cytoskeleton is a suppressor of the endogenous skewing behaviour of Arabidopsis primary roots in microgravity

by on 22 August 2016in Biology & Biotechnology No comment

Before plants can be effectively utilised as a component of enclosed life-support systems for space exploration, it is important to understand the molecular mechanisms by which they develop in microgravity. Using the Biological Research in Canisters (BRIC) hardware on board the second to the last flight of the Space Shuttle Discovery (STS-131 mission), we studied how microgravity impacts root growth in Arabidopsis thaliana. Ground-based studies showed that the actin cytoskeleton negatively regulates root gravity responses on Earth, leading us to hypothesise that actin might also be an important modulator of root growth behaviour in space. We investigated how microgravity impacted root growth of wild type (ecotype Columbia) and a mutant (act2-3) disrupted in a root-expressed vegetative actin isoform (ACTIN2). Roots of etiolated wild-type and act2-3 seedlings grown in space skewed vigorously toward the left, which was unexpected given the reduced directional cue provided by gravity. The left-handed directional root growth in space was more pronounced in act2-3 mutants than wild type. To quantify differences in root orientation of these two genotypes in space, we developed an algorithm where single root images were converted into binary images using computational edge detection methods. Binary images were processed with Fast Fourier Transformation (FFT), and histogram and entropy were used to determine spectral distribution, such that high entropy values corresponded to roots that deviated more strongly from linear orientation whereas low entropy values represented straight roots. We found that act2-3 roots had a statistically stronger skewing/coiling response than wild-type roots, but such differences were not apparent on Earth. Ultrastructural studies revealed that newly developed cell walls of space-grown act2-3 roots were more severely disrupted compared to space-grown wild type, and ground control wild-type and act2-3 roots. Collectively, our results provide evidence that, like root gravity responses on Earth, endogenous directional growth patterns of roots in microgravity are suppressed by the actin cytoskeleton. Modulation of root growth in space by actin could be facilitated in part through its impact on cell wall architecture.

Related URLs:
http://www.ncbi.nlm.nih.gov/pubmed/23952736

Morphometric analyses of petioles of seedlings grown in a spaceflight experiment

by on 22 August 2016in Biology & Biotechnology No comment

Gravity is a constant unidirectional stimulus on Earth, and gravitropism in plants involves three phases: perception, transduction, and response. In shoots, perception takes place within the endodermis. To investigate the cellular machinery of perception in microgravity, we conducted a spaceflight study with Arabidopsis thaliana seedlings, which were grown in microgravity in darkness using the Biological Research in Canisters (BRIC) hardware during space shuttle mission STS-131. In the 14-day-old etiolated plants, we studied seedling development and the morphological parameters of the endodermal cells in the petiole. Seedlings from the spaceflight experiment (FL) were compared to a ground control (GC), which both were in the BRIC flight hardware. In addition, to assay any potential effects from growth in spaceflight hardware, we performed another control by growing seedlings in Petri dishes in standard laboratory conditions (termed the hardware control, HC). Seed germination was significantly lower in samples grown in flight hardware (FL, GC) compared to the HC. In terms of cellular parameters of endodermal cells, the greatest differences also were between seedlings grown in spaceflight hardware (FL, GC) compared to those grown outside of this hardware (HC). Specifically, the endodermal cells were significantly smaller in seedlings grown in the BRIC system compared to those in the HC. However, a change in the shape of the cell, suggesting alterations in the cell wall, was one parameter that appears to be a true microgravity effect. Taken together, our results suggest that caution must be taken when interpreting results from the increasingly utilized BRIC spaceflight hardware system and that it is important to perform additional ground controls to aid in the analysis of spaceflight experiments.

Related URLs:
http://www.ncbi.nlm.nih.gov/pubmed/26376793

Testing the Bio-compatibility of Aluminum PDFU BRIC Hardware

by on 22 August 2016in Biology & Biotechnology No comment

Biological research in an orbital environment necessitates the containment of the sample and its associated chemical fixatives. The Biological Research in Canisters (BRIC) hardware developed by Kennedy Space Center has been widely used in several configurations to support biological experiments on the Shuttle and the International Space Station (ISS). The current model of BRIC hardware contains six Petri Dish Fixation Units (PDFUs), each of which holds one Petri plate containing the specimen. This study compares traditional polycarbonate PDFUs to PDFUs primarily composed of aluminum with respect to their biocompatibility with Arabidopsis thaliana (Arabidopsis) growth and development. Seeds were planted on nutrient agar plates and inserted into either polycarbonate or aluminum PDFUs, which were then secured in the BRIC hardware. Plates were allowed to develop in the PDFUs in the dark for a period of 12 days, after which they were preserved by either RNAlater or glutaraldehyde, harvested, photographed, RNA- extracted, and prepared for gene expression analyses. Direct comparison of the etiolated Arabidopsis seedlings from the polycarbonate and aluminum PDFUs presented no discernible morphological differences, nor were there any significant differences between the expression levels of several target genes chosen for their sensitivity in reporting an aluminum stress response.

Related URLs:
http://gravitationalandspacebiology.org/index.php/journal/article/view/591

Survival of plant seeds, their UV screens, and nptII DNA for 18 months outside the International Space Station

by on 9 June 2015in Education No comment

The plausibility that life was imported to Earth from elsewhere can be tested by subjecting life-forms to space travel. Ultraviolet light is the major liability in short-term exposures (Horneck et al., 2001 ), and plant seeds, tardigrades, and lichens-but not microorganisms and their spores-are candidates for long-term survival (Anikeeva et al., 1990 ; Sancho et al., 2007 ; Jonsson et al., 2008 ; de la Torre et al., 2010 ). In the present study, plant seeds germinated after 1.5 years of exposure to solar UV, solar and galactic cosmic radiation, temperature fluctuations, and space vacuum outside the International Space Station. Of the 2100 exposed wild-type Arabidopsis thaliana and Nicotiana tabacum (tobacco) seeds, 23% produced viable plants after return to Earth. Survival was lower in the Arabidopsis Wassilewskija ecotype and in mutants (tt4-8 and fah1-2) lacking UV screens. The highest survival occurred in tobacco (44%). Germination was delayed in seeds shielded from solar light, yet full survival was attained, which indicates that longer space travel would be possible for seeds embedded in an opaque matrix. We conclude that a naked, seed-like entity could have survived exposure to solar UV radiation during a hypothetical transfer from Mars to Earth. Chemical samples of seed flavonoid UV screens were degraded by UV, but their overall capacity to absorb UV was retained. Naked DNA encoding the nptII gene (kanamycin resistance) was also degraded by UV. A fragment, however, was detected by the polymerase chain reaction, and the gene survived in space when protected from UV. Even if seeds do not survive, components (e.g., their DNA) might survive transfer over cosmic distances.

Related URLs:
http://www.ncbi.nlm.nih.gov/pubmed/22680697

Rocket seedling production on the international space station: Growth and nutritional properties

by on 9 June 2015in Education No comment

Producing sprouts directly during space missions may represent an interesting opportunity to offer high-quality fresh ready to eat food to the astronauts. The goal of this work was to compare, in terms of growth and nutritional quality, rocket (Eruca sativa Mill.) seedlings grown in the International Space Station during the ENEIDE mission with those grown in a ground-based experiment (in presence and absence of clinorotation). The rocket seedlings obtained from the space-experiment were thinner and more elongated than those obtained in the ground-based experiment. Cotyledons were often closed in the seedlings grown in the space experiment. Quantitative (germination, fresh and dry weight) and qualitative (glucose, fructose, sucrose and starch) traits of rocket seedling were negatively affected by micrograv-ity, especially those recorded on seedlings grown under real microgravity conditions The total chlorophyll, and carotenoids of seedlings obtained in the space experiment were strongly reduced in comparison to those obtained in the ground-based experiment (presence and absence of clinorotation). The results showed that it is possible to produce rocket seedlings in the ISS; however, further studies are needed to define the optimal environmental conditions for producing rocket seedlings with high nutritional value.

Related URLs:
http://dx.doi.org/10.1007/BF02919465

Growth and Morphogenesis of Azuki Bean Seedlings in Space during SSAF2013 Program

by on 9 June 2015in Education No comment

Seedlings of azuki bean were cultivated under microgravity conditions in space during SSAF2013 program, and then growth, morphology, and the cell wall rigidity of their etiolated epicotyls were analyzed. Epicotyls grown on the ground oriented vertical direction, whereas epicotyls grown in space oriented oblique upward direction away from the cotyledons. The length of epicotyls grown in space was varied, but the proportion of seedlings with larger epicotyls was higher than that of the controls. These results indicate that growth and morphology of epicotyls are modified under microgravity conditions in space. On the other hand, the breaking load of epicotyls was analyzed using a spring balance for determination of the cell wall rigidity of epicotyls. The breaking load of epicotyls grown in space tended to be smaller than that of controls. Also, epicotyls grown in space had resistance to bending than the controls. Thus, microgravity affected the cell wall rigidity of epicotyls. Taken together, azuki bean seedlings performed an automorphogenesis and cell wall modification under microgravity conditions. Under microgravity conditions, where plants need not to resist the gravitational force, the body shape and the cell wall rigidity of stems may be modified.

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Cell wall-bound peroxidase activity and lignin formation in azuki bean epicotyls grown under hypergravity conditions

by on 9 June 2015in Biology & Biotechnology No comment

The effects of accelerated gravity stimuli on the cell wall-bound peroxidase activity and the lignin content were investigated along epicotyls of azuki bean (Vigna angularis) seedlings. The endogenous growth occurred primarily in the upper regions of the epicotyl, but no growth was detected in the middle or basal regions. Hypergravity treatment at 300g for 6h suppressed elongation growth and stimulated lateral expansion of the upper regions. The content of acetyl bromide-soluble lignin increased gradually from the apical to the basal regions of epicotyls. Hypergravity treatment stimulated the increase in the lignin content in epicotyls, particularly in the middle and basal regions. The peroxidase activity in the protein fraction extracted with a high ionic strength buffer from the cell wall preparation also increased gradually toward the basal region, and hypergravity treatment increased the activity in all epicotyl regions. There was a close correlation between the lignin content and the enzyme activity. These results suggest that hypergravity increases the activity of cell wall-bound peroxidase followed by increases of the lignin formation in epicotyl cell walls, which may contribute to increasing the rigidity of cell walls against the gravitational force.

Related URLs:
http://www.ncbi.nlm.nih.gov/pubmed/19195738