Cell cycle acceleration and changes in essential nuclear functions induced by simulated microgravity in a synchronized Arabidopsis cell culture

Alteration in the callogenesis, tropane alkaloid formation, and gene expression in Hyoscyamus niger under clinorotation

This study aimed to investigate the effects of clinorotation induced by 2-D clinostat on the growth, tropane alkaloid production, gene expression, antioxidant capacity, and cellular defense responses in the callus tissue of Hyoscyamus niger. Callus induction was conducted by putting hypocotyl explants in the MS culture medium supplemented with 1 mgL-1 2,4-D and 1 mgL-1 BAP growth regulators. The sub-cultured calli were placed on a clinostat for 0, 3, 7, and 10 days (2.24 × 10-5 g on the edge of the callus ring). Clinorotation significantly increased callus fresh weight, dry weight, protein, carbohydrate, and proline contents compared to the control, and their maximum contents were obtained after 7 and 10 days. H2O2 level enhanced under clinorotation with a 76.3% rise after 10 days compared to control and positively affected the atropine (77.1%) and scopolamine (69.2%) productions. Hyoscyamine 6-beta hydroxylase and putrescine N-methyltransferase gene expression involved in the tropane alkaloid biosynthesis were upregulated markedly with 14.2 and 17.1-folds increase after 10 days of clinorotation, respectively. The expressions of jasmonic acid, mitogen-activated protein kinase, and ethylene-responsive element-binding transcription factor were upregulated, and the activity of peroxidase and catalase showed a 72.7 and 80% rise after 10 days. These findings suggest that microgravity can enhance callogenesis by stimulating the ROS level, which can impact the antioxidant enzymes, tropane alkaloid formation, and gene expression.

Epigenetic modifications of 45S rDNA associates with the disruption of nucleolar organisation during Cd stress response in Pakchoi

The role of the nucleolus in Pakchoi response to Cd stress remains largely unknown. In this work, we focus on exploring the underling mechanism between nucleolus disruption and epigenetic modification in Cd stressed-Pakchoi. Our results indicated that the proportion of nucleolus disruption, decondensation of 45 S rDNA chromatin, and a simultaneous increase in 5' external transcribed spacer region (ETS) transcription were observed with increasing Cd concentration, accompanied by genome-wide alterations in the levels of histone acetylation and methylation. Further results showed that Cd treatment exhibited a significant increase in H3K9ac, H4K5ac, and H3K9me2 levels occurred in promoter regions of the 45 S rDNA. Additionally, DNA methylation assays in the 45 S rDNA promoter region revealed that individual site-specific hypomethylation may be engaged in the activation of 45 S rDNA transcription. Our study provides some molecular mechanisms for the linkage between Cd stress, rDNA epigenetic modifications, and nucleolus disintegration in plants.

Advances in Microgravity Directed Tissue Engineering

Tissue engineering aims to generate functional biological substitutes to repair, sustain, improve, or replace tissue function affected by disease. With the rapid development of space science, the application of simulated microgravity has become an active topic in the field of tissue engineering. There is a growing body of evidence demonstrating that microgravity offers excellent advantages for tissue engineering by modulating cellular morphology, metabolism, secretion, proliferation, and stem cell differentiation. To date, there have been many achievements in constructing bioartificial spheroids, organoids, or tissue analogs with or without scaffolds in vitro under simulated microgravity conditions. Herein, the current status, recent advances, challenges, and prospects of microgravity related to tissue engineering are reviewed. Current simulated-microgravity devices and cutting-edge advances of microgravity for biomaterials-dependent or biomaterials-independent tissue engineering to offer a reference for guiding further exploration of simulated microgravity strategies to produce engineered tissues are summarized and discussed.

Perspectives for plant biology in space and analogue environments

Advancements in plant space biology are required for the realization of human space exploration missions, where the re-supply of resources from Earth is not feasible. Until a few decades ago, space life science was focused on the impact of the space environment on the human body. More recently, the interest in plant space biology has increased because plants are key organisms in Bioregenerative Life Support Systems (BLSS) for the regeneration of resources and fresh food production. Moreover, plants play an important role in psychological support for astronauts. The definition of cultivation requirements for the design, realization, and successful operation of BLSS must consider the effects of space factors on plants. Altered gravitational fields and radiation exposure are the main space factors inducing changes in gene expression, cell proliferation and differentiation, signalling and physiological processes with possible consequences on tissue organization and organogenesis, thus on the whole plant functioning. Interestingly, the changes at the cellular and molecular levels do not always result in organismic or developmental changes. This apparent paradox is a current research challenge. In this paper, the main findings of gravity- and radiation-related research on higher plants are summarized, highlighting the knowledge gaps that are still necessary to fill. Existing experimental facilities to simulate the effect of space factors, as well as requirements for future facilities for possible experiments to achieve fundamental biology goals are considered. Finally, the need for making synergies among disciplines and for establishing global standard operating procedures for analyses and data collection in space experiments is highlighted.

Cellular and Molecular Signaling Meet the Space Environment

During space missions that travel beyond the cocoon of the Earth's magnetosphere, astronauts are subjected to the microgravity and radiation stressors of outer space [...].

A protocol for measuring the response of Arabidopsis roots to gravity and treatment for simulated microgravity

We present a protocol to quantify the response of both normal and mutant Arabidopsis seedlings to gravity and simulated microgravity under earth-normal gravity conditions. We describe the steps to simulate microgravity using a three-dimensional (3D) clinostat, which changes the rate and direction at random and consistently rotates the axis horizontally and vertically to counteract the standard gravity at the Earth's surface. We then detail the gravity stimulation experiment, followed by the assessment of root responses using ImageJ-based analysis. For complete details on the use and execution of this protocol, please refer to Xu et al. (2022).1.

Red Light Enhances Plant Adaptation to Spaceflight and Mars g-Levels

Understanding how plants respond and adapt to extraterrestrial conditions is essential for space exploration initiatives. Deleterious effects of the space environment on plant development have been reported, such as the unbalance of cell growth and proliferation in the root meristem, or gene expression reprogramming. However, plants are capable of surviving and completing the seed-to-seed life cycle under microgravity. A key research challenge is to identify environmental cues, such as light, which could compensate the negative effects of microgravity. Understanding the crosstalk between light and gravity sensing in space was the major objective of the NASA-ESA Seedling Growth series of spaceflight experiments (2013–2018). Different g-levels were used, with special attention to micro-g, Mars-g, and Earth-g. In spaceflight seedlings illuminated for 4 days with a white light photoperiod and then photostimulated with red light for 2 days, transcriptomic studies showed, first, that red light partially reverted the gene reprogramming induced by microgravity, and that the combination of microgravity and photoactivation was not recognized by seedlings as stressful. Two mutant lines of the nucleolar protein nucleolin exhibited differential requirements in response to red light photoactivation. This observation opens the way to directed-mutagenesis strategies in crop design to be used in space colonization. Further transcriptomic studies at different g-levels showed elevated plastid and mitochondrial genome expression in microgravity, associated with disturbed nucleus–organelle communication, and the upregulation of genes encoding auxin and cytokinin hormonal pathways. At the Mars g-level, genes of hormone pathways related to stress response were activated, together with some transcription factors specifically related to acclimation, suggesting that seedlings grown in partial-g are able to acclimate by modulating genome expression in routes related to space-environment-associated stress.

Plants in Microgravity: Molecular and Technological Perspectives

Plants are vital components of our ecosystem for a balanced life here on Earth, as a source of both food and oxygen for survival. Recent space exploration has extended the field of plant biology, allowing for future studies on life support farming on distant planets. This exploration will utilize life support technologies for long-term human space flights and settlements. Such longer space missions will depend on the supply of clean air, food, and proper waste management. The ubiquitous force of gravity is known to impact plant growth and development. Despite this, we still have limited knowledge about how plants can sense and adapt to microgravity in space. Thus, the ability of plants to survive in microgravity in space settings becomes an intriguing topic to be investigated in detail. The new knowledge could be applied to provide food for astronaut missions to space and could also teach us more about how plants can adapt to unique environments. Here, we briefly review and discuss the current knowledge about plant gravity-sensing mechanisms and the experimental possibilities to research microgravity-effects on plants either on the Earth or in orbit.

Static and Electromagnetic Fields Differently Affect Proliferation and Cell Death Through Acid Enhancement of ROS Generation in Mesenchymal Stem Cells

Magnetic fields remotely influence cellular homeostasis as a physical agent through the changes in cell physicochemical reactions. Magnetic fields affect cell fate, which may provide an important and interesting challenge in stem cell behaviors. Here, we investigated the effects of the static magnetic field (SMF, 20 mT) and electromagnetic field (EMF, 20 mT-50 Hz) on reactive oxygen species (ROS) production and the acidic pH conditions as stimuli to change cell cycle progression and cell death in mesenchymal stem cells. Results show that SMF, EMF, and their simultaneous (SMF+EMF) administration increase ROS and expression of nuclear factor erythroid 2-related factor 2 (Nrf2), superoxide dismutase 2 (SOD2), and glutathione-S-transferase (GST) as an antioxidant defense system. Besides, intracellular pH (pHi) decreases in presence of either EMF or SMF+EMF, but not SMF. Decreased ROS content using ascorbic acid in these treatments leads to increased pH compared to the magnetic field treatments alone. Furthermore, each magnetic field has different effects on the cellular process of stem cells, including cell cycle, apoptosis and necrosis. Moreover, treatment by SMF enhances the cell viability after 24 h, while EMF or SMF+EMF decreases it. These observations indicate that fluctuations of ROS generation and acid enhancement during SMF and EMF treatments may reveal their beneficial and adverse effects on the molecular and cellular mechanisms involved in the growth, death, and differentiation of stem cells.

Space omics research in Europe: Contributions, geographical distribution and ESA member state funding schemes

The European research community, via European Space Agency (ESA) spaceflight opportunities, has significantly contributed toward our current understanding of spaceflight biology. Recent molecular biology experiments include "omic" analysis, which provides a holistic and systems level understanding of the mechanisms underlying phenotypic adaptation. Despite vast interest in, and the immense quantity of biological information gained from space omics research, the knowledge of ESA-related space omics works as a collective remains poorly defined due to the recent exponential application of omics approaches in space and the limited search capabilities of pre-existing records. Thus, a review of such contributions is necessary to clarify and promote the development of space omics among ESA and ESA state members. To address this gap, in this review, we i) identified and summarized omics works led by European researchers, ii) geographically described these omics works, and iii) highlighted potential caveats in complex funding scenarios among ESA member states.

Alterations in endogenous hormone levels and energy metabolism promoted the induction, differentiation and maturation of Begonia somatic embryos under clinorotation

The present study provides a visual insight into the effects of simulated microgravity (MG) on somatic embryogenesis (SE) in Begonia through the analysis of phytohormone fluctuations and energy metabolism. To investigate this relationship, thin cell layer culture model was first used. The results showed that MG changed the phytohormone content and stimulated starch biosynthesis to convert into sugar to release energy needed for regeneration and proliferation. Moreover, from the results it is likely that MG accelerated the initiation and subsequently maturation and aging of SE via decrease of AUX and increase of ABA. High content of GA, CKs, starch, sugar and low ABA as well as high CKs/ABA ratio were responsible for the increase in the number of embryos under clinorotation which was 1.57-fold higher than control after 90 days. The increase in fresh and dry weight of somatic embryos and chlorophyll content under MG were confirmed as their adaptive responses to gravitational stress. However, long-term exposure to MG (120 days) stimulated biosynthesis of ABA levels 1.85-fold higher than controls, which resulted in a decrease in chlorophyll content, increase in number of mature embryos and stomata length. These results revealed that MG regulated the induction, differentiation and senescence of somatic embryos via a biochemical interaction pathway.

Use of Reduced Gravity Simulators for Plant Biological Studies

Simulated microgravity and partial gravity research on Earth is a necessary complement to space research in real microgravity due to limitations of access to spaceflight. However, the use of ground-based facilities for reduced gravity simulation is far from simple. Microgravity simulation usually results in the need to consider secondary effects that appear in the generation of altered gravity. These secondary effects may interfere with gravity alteration in the changes observed in the biological processes under study. In addition to microgravity simulation, ground-based facilities are also capable of generating hypergravity or fractional gravity conditions whose effects on biological systems are worth being tested and compared with the results of microgravity exposure. Multiple technologies (2D clinorotation, random positioning machines, magnetic levitators, or centrifuges) and experimental hardware (different containers and substrates for seedlings or cell cultures) are available for these studies. Experimental requirements should be collectively and carefully considered in defining the optimal experimental design, taking into account that some environmental parameters, or life-support conditions, could be difficult to be provided in certain facilities. Using simulation facilities will allow us to anticipate, modify, or redefine the findings provided by the scarce available spaceflight opportunities.

Potential evidence for transgenerational epigenetic memory in Arabidopsis thaliana following spaceflight

Plants grown in spaceflight exhibited differential methylation responses and this is important because plants are sessile, they are constantly exposed to a variety of environmental pressures and respond to them in many ways. We previously showed that the Arabidopsis genome exhibited lower methylation level after spaceflight for 60 h in orbit. Here, using the offspring of the seedlings grown in microgravity environment in the SJ-10 satellite for 11 days and returned to Earth, we systematically studied the potential effects of spaceflight on DNA methylation, transcriptome, and phenotype in the offspring. Whole-genome methylation analysis in the first generation of offspring (F₁) showed that, although there was no significant difference in methylation level as had previously been observed in the parent plants, some residual imprints of DNA methylation differences were detected. Combined DNA methylation and RNA-sequencing analysis indicated that expression of many pathways, such as the abscisic acid-activated pathway, protein phosphorylation, and nitrate signaling pathway, etc. were enriched in the F₁ population. As some phenotypic differences still existed in the F₂ generation, it was suggested that these epigenetic DNA methylation modifications were partially retained, resulting in phenotypic differences in the offspring. Furthermore, some of the spaceflight-induced heritable differentially methylated regions (DMRs) were retained. Changes in epigenetic modifications caused by spaceflight affected the growth of two future seed generations. Altogether, our research is helpful in better understanding the adaptation mechanism of plants to the spaceflight environment.

In order to investigate whether the effects of spaceflight on plants persist in future generations, Xu et al studied the offspring of Arabidopsis thaliana seedlings that had been grown in a microgravity environment for 11 days. They found that epigenetic modifications caused by spaceflight potentially affected the growth of two future seed generations, shedding light on the longevity of the effects of spaceflight on plants.

Modulation of cell cycle progression and chromatin dynamic as tolerance mechanisms to salinity and drought stress in maize

Salinity and drought are the major abiotic stresses that disturb several aspects of maize plants growth at the cellular level, one of these aspects is cell cycle machinery. In our study, we dissected the molecular alterations and downstream effectors of salinity and drought stress on cell cycle regulation and chromatin remodeling. Effects of salinity and drought stress were determined on maize seedlings using 200 mM NaCl (induced salinity stress), and 250 mM mannitol (induced drought stress) treatments, then cell cycle progression and chromatin remodeling dynamics were investigated. Seedlings displayed severe growth defects, including inhibition of root growth. Interestingly, stress treatments induced cell cycle arrest in S-phase with extensive depletion of cyclins B1 and A1. Further investigation of gene expression profiles of cell cycle regulators showed the downregulation of the CDKA, CDKB, CYCA, and CYCB. These results reveal the direct link between salinity and drought stress and cell cycle deregulation leading to a low cell proliferation rate. Moreover, abiotic stress alters chromatin remodeling dynamic in a way that directs the cell cycle arrest. We observed low DNA methylation patterns accompanied by dynamic histone modifications that favor chromatin decondensation. Also, the high expression of DNA topoisomerase 2, 6 family was detected as consequence of DNA damage. In conclusion, in response to salinity and drought stress, maize seedlings exhibit modulation of cell cycle progression, resulting in the cell cycle arrest through chromatin remodeling.

Crude Methanol Extract of Rosin Gum Exhibits Specific Cytotoxicity against Human Breast Cancer Cells via Apoptosis Induction

BACKGROUND

Rosin (Colophony) is a natural resin derived from species of the pine family Pinaceae. It has wide industrial applications including printing inks, photocopying paper, adhesives and varnishes, soap and soda. Rosin and its derivatives are employed as ingredients in various pharmaceutical products such as ointments and plasters. Rosin-based products contain allergens that may exert some occupational health problems such as asthma and contact dermatitis.

OBJECTIVE

Our knowledge of the pharmaceutical and medicinal properties of rosin is limited. The current study aims at investigating the cytotoxic potential of Rosin-Derived Crude Methanolic Extract (RD-CME) and elucidation of its mode-of-action against breast cancer cells (MCF-7 and MDA-MB231).

METHODS

Crude methanol extract was prepared from rosin. Its phenolic contents were analyzed by Reversed- Phase High-Performance Liquid Chromatography (RP-HPLC). Antioxidant activity was evaluated by DPPH radical-scavenging assay. Antiproliferation activity against MCF-7 and MDA-MB231 cancerous cells was investigated by MTT assay; its potency compared with doxorubicin as positive control and specificity were assessed compared to two non-cancerous cell lines (BJ-1 and MCF-12F). Selected apoptosis protein markers were assayed by western blotting. Cell cycle analysis was performed by Annexin V-FITC/PI FACS assay.

RESULTS

RD-CME exhibited significant and selective cytotoxicity against the two tested breast cancer cells (MCF-7 and MDA-MB231) compared to normal cells as revealed by MTT assay. ELISA and western blotting indicated that the observed antiproliferative activity of RD-CME is mediated via the engagement of an intrinsic apoptosis signaling pathway, as judged by enhanced expression of key pro-apoptotic protein markers (p53, Bax and Casp 3) relative to vehicle solvent-treated MCF-7 control cells.

CONCLUSION

To our knowledge, this is the first report to investigate the medicinal anticancer and antioxidant potential of crude methanolic extract derived from colophony rosin. We provided evidence that RD-CME exhibits strong antioxidant and anticancer effects. The observed cytotoxic activity against MCF-7 is proposed to take place via G2/M cell cycle arrest and apoptosis. Colophony resin has a great potential to join the arsenal of plantderived natural anticancer drugs. Further thorough investigation of the potential cytotoxicity of RD-CME against various cancerous cell lines is required to assess the spectrum and potency of its novel activity.

Module to Support Real-Time Microscopic Imaging of Living Organisms on Ground-Based Microgravity Analogs

Since opportunities for spaceflight experiments are scarce, ground-based microgravity simulation devices (MSDs) offer accessible and economical alternatives for gravitational biology studies. Among the MSDs, the random positioning machine (RPM) provides simulated microgravity conditions on the ground by randomizing rotating biological samples in two axes to distribute the Earth’s gravity vector in all directions over time. Real-time microscopy and image acquisition during microgravity simulation are of particular interest to enable the study of how basic cell functions, such as division, migration, and proliferation, progress under altered gravity conditions. However, these capabilities have been difficult to implement due to the constantly moving frames of the RPM as well as mechanical noise. Therefore, we developed an image acquisition module that can be mounted on an RPM to capture live images over time while the specimen is in the simulated microgravity (SMG) environment. This module integrates a digital microscope with a magnification range of 20× to 700×, a high-speed data transmission adaptor for the wireless streaming of time-lapse images, and a backlight illuminator to view the sample under brightfield and darkfield modes. With this module, we successfully demonstrated the real-time imaging of human cells cultured on an RPM in brightfield, lasting up to 80 h, and also visualized them in green fluorescent channel. This module was successful in monitoring cell morphology and in quantifying the rate of cell division, cell migration, and wound healing in SMG. It can be easily modified to study the response of other biological specimens to SMG.

Flow Cytometry and Sorting in Arabidopsis

Flow cytometry and sorting represents a valuable and mature experimental platform for the analysis of cellular populations. Applications involving higher plants started to emerge around 40 years ago and are now widely employed both to provide unique information regarding basic and applied questions in the biosciences and to advance agricultural productivity in practical ways. Further development of this platform is being actively pursued, and this promises additional progress in our understanding of the interactions of cells within complex tissues and organs. Higher plants offer unique challenges in terms of flow cytometric analysis, first since their organs and tissues are, almost without exception, three-dimensional assemblies of different cell types held together by tough cell walls, and, second, because individual plant cells are generally larger than those of mammals.This chapter, which updates work last reviewed in 2014 [Galbraith DW (2014) Flow cytometry and sorting in Arabidopsis. In: Sanchez Serrano JJ, Salinas J (eds) Arabidopsis Protocols, 3rd ed. Methods in molecular biology, vol 1062. Humana Press, Totowa, pp 509-537], describes the application of techniques of flow cytometry and sorting to the model plant species Arabidopsis thaliana, in particular emphasizing (a) fluorescence labeling in vivo of specific cell types and of subcellular components, (b) analysis using both conventional cytometers and spectral analyzers, (c) fluorescence-activated sorting of protoplasts and nuclei, and (d) transcriptome analyses using sorted protoplasts and nuclei, focusing on population analyses at the level of single protoplasts and nuclei. Since this is an update, details of new experimental methods are emphasized.

Evaluation of Laser Effects on the Human Body After Laser Therapy

Lasers have wide applications in the treatment and diagnosis of diseases and various medical fields. Laser therapy like the other methods has advantages and disadvantages. Some risks such as bleeding, pain, and infection are created after laser therapy. Explanation and evaluation of laser effects on cell function, tissue, and the body are the aims of this study. We reviewed papers available from 1986 to 2019 about the effects of lasers on cells and tissue. An online search of PubMed, Science Direct and Google scholar using such keywords as "laser", "cell", "tissue", "body" and "side effects" was performed. The laser photons are absorbed by chromophores, resulting in the target heating and localized damage. Laser irradiation alters cellular metabolism and cellular functions. These alterations may be accompanied by undesired side effects which can be monitored via metabolites level change in the body. Based on this finding, laser therapy may be associated with several side effects and complications; therefore, before treatment, the determination of laser types and their properties is necessary to avoid creating side effects. The advantages and disadvantages of the treatment type should be considered in order to choose the best treatment with the least side effects. The patients' awareness of possible side effects before treatment and also an effective follow-up and management of patients after action are two important points in laser therapy. Training curriculum definition should be determined for laser applicant qualifications in different medical fields.

Comparison of Microgravity Analogs to Spaceflight in Studies of Plant Growth and Development

Life on Earth has evolved under the influence of gravity. This force has played an important role in shaping development and morphology from the molecular level to the whole organism. Although aquatic life experiences reduced gravity effects, land plants have evolved under a 1-g environment. Understanding gravitational effects requires changing the magnitude of this force. One method of eliminating gravity''s influence is to enter into a free-fall orbit around the planet, thereby achieving a balance between centripetal force of gravity and the centrifugal force of the moving object. This balance is often mistakenly referred to as microgravity, but is best described as weightlessness. In addition to actually compensating gravity, instruments such as clinostats, random-positioning machines (RPM), and magnetic levitation devices have been used to eliminate effects of constant gravity on plant growth and development. However, these platforms do not reduce gravity but constantly change its direction. Despite these fundamental differences, there are few studies that have investigated the comparability between these platforms and weightlessness. Here, we provide a review of the strengths and weaknesses of these analogs for the study of plant growth and development compared to spaceflight experiments. We also consider reduced or partial gravity effects via spaceflight and analog methods. While these analogs are useful, the fidelity of the results relative to spaceflight depends on biological parameters and environmental conditions that cannot be simulated in ground-based studies.

RNA-seq analyses of Arabidopsis thaliana seedlings after exposure to blue-light phototropic stimuli in microgravity

PREMISE

Plants synthesize information from multiple environmental stimuli when determining their direction of growth. Gravity, being ubiquitous on Earth, plays a major role in determining the direction of growth and overall architecture of the plant. Here, we utilized the microgravity environment on board the International Space Station (ISS) to identify genes involved influencing growth and development of phototropically stimulated seedlings of Arabidopsis thaliana.

METHODS

Seedlings were grown on the ISS, and RNA was extracted from 7 samples (pools of 10-15 plants) grown in microgravity (μg) or Earth gravity conditions (1-g). Transcriptomic analyses via RNA sequencing (RNA-seq) of differential gene expression was performed using the HISAT2-Stringtie-DESeq2 RNASeq pipeline. Differentially expressed genes were further characterized by using Pathway Analysis and enrichment for Gene Ontology classifications.

RESULTS

For 296 genes that were found significantly differentially expressed between plants in microgravity compared to 1-g controls, Pathway Analysis identified eight molecular pathways that were significantly affected by reduced gravity conditions. Specifically, light-associated pathways (e.g., photosynthesis-antenna proteins, photosynthesis, porphyrin, and chlorophyll metabolism) were significantly downregulated in microgravity.

CONCLUSIONS

Gene expression in A. thaliana seedlings grown in microgravity was significantly altered compared to that of the 1-g control. Understanding how plants grow in conditions of microgravity not only aids in our understanding of how plants grow and respond to the environment but will also help to efficiently grow plants during long-range space missions.