Radiobiological investigations in Cosmos 782 space flight (Biobloc SF1 experiment)

Simulated galactic cosmic ray exposure activates dose-dependent DNA repair response and down regulates glucosinolate pathways in arabidopsis seedlings

Outside the protection of Earth's magnetic field, organisms are constantly exposed to space radiation consisting of energetic protons and other heavier charged particles. With the goal of crewed Mars exploration, the production of fresh food during long duration space missions is critical for meeting astronauts' nutritional and psychological needs. However, the biological effects of space radiation on plants have not been sufficiently investigated and characterized. To that end, 10-day-old Arabidopsis seedlings were exposed to simulated Galactic Cosmic Rays (GCR) and assessed for transcriptomic changes. The simulated GCR irradiation was carried out in the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Lab (BNL). The exposures were conducted acutely for two dose points at 40 cGy or 80 cGy, with sequential delivery of proton, helium, oxygen, silicon, and iron ions. Control and irradiated seedlings were then harvested and preserved in RNAlater at 3 hrs post irradiation. Total RNA was isolated for transcriptomic analyses using RNAseq. The data revealed that the transcriptomic responses were dose-dependent, with significant upregulation of DNA repair pathways and downregulation of glucosinolate biosynthetic pathways. Glucosinolates are important for plant pathogen defense and for the taste of a plant, which are both relevant to growing plants for spaceflight. These findings fill in knowledge gaps of how plants respond to radiation in beyond-Earth environments.

Response of Arabidopsis thaliana and Mizuna Mustard Seeds to Simulated Space Radiation Exposures

One of the major concerns for long-term exploration missions beyond the Earth’s magnetosphere is consequences from exposures to solar particle event (SPE) protons and galactic cosmic rays (GCR). For long-term crewed Lunar and Mars explorations, the production of fresh food in space will provide both nutritional supplements and psychological benefits to the astronauts. However, the effects of space radiation on plants and plant propagules have not been sufficiently investigated and characterized. In this study, we evaluated the effect of two different compositions of charged particles-simulated GCR, and simulated SPE protons on dry and hydrated seeds of the model plant Arabidopsis thaliana and the crop plant Mizuna mustard [Brassica rapa var. japonica]. Exposures to charged particles, simulated GCRs (up to 80 cGy) or SPEs (up to 200 cGy), were performed either acutely or at a low dose rate using the NASA Space Radiation Laboratory (NSRL) facility at Brookhaven National Lab (BNL). Control and irradiated seeds were planted in a solid phytogel and grown in a controlled environment. Five to seven days after planting, morphological parameters were measured to evaluate radiation-induced damage in the seedlings. After exposure to single types of charged particles, as well as to simulated GCR, the hydrated Arabidopsis seeds showed dose- and quality-dependent responses, with heavier ions causing more severe defects. Seeds exposed to simulated GCR (dry seeds) and SPE (hydrated seeds) had significant, although much less damage than seeds exposed to heavier and higher linear energy transfer (LET) particles. In general, the extent of damage depends on the seed type.

HZE particle effects in space

Among the various particulate components of ionizing radiation in space, heavy ions (the so-called HZE particles) have been of special concern to radiobiologists. To understand the ways by which HZE particles of cosmic radiation interact with biological systems, methods have been developed to precisely localize the trajectory of an HZE particle relative to the biological object and to correlate the physical data of the particle with the biological effects observed along its path. In a variety of test systems, injuries were traced back to the traversal of a single HZE particle, such as somatic mutations, and chromosomal aberrations in plant seeds, development disturbances and malformations in insect and salt shrimp embryos, or cell death in bacterial spores. In the latter case, a long-ranging killing effect around the particle's track was observed. Whereas, from spaceflight experiments, substantial infomation has been accumulated on single HZE particle effects in resting systems and in a few embryonic systems, there is a paucity of data on cosmic radiation effects in whole tissues or animals, especially mammalians.

Influence of a long duration exposure, 69 months, to the space flight factors in Artemia cysts, tobacco and rice seeds

Three french laboratories have participated in the Free Flyer Biostack experiment. Artemia cysts, tobacco seeds and rice caryopsis and embryos were used. Biological objects in monolayers were dead. In opposite, a large fraction of samples used in bulk survived. A stimulatory effect occurred in the first steps of development in Artemia cysts. In fact, the larval survival was unchanged or slightly reduced. In tobacco a drastic decrease in germination and survival rate was observed. Space flight did not induce genetic changes. In rice, results depend on the variety which was investigated; the growth rate stimulation in flight samples is discussed with respect to controls.

Investigations of the effects of cosmic rays on Artemia cysts and tobacco seeds; results of Exobloc II experiment, flown aboard Biocosmos 1887

Artemia (Brine shrimp) cysts and tobacco seeds, dormant biological material devoid of metabolic activity, were flown aboard the Soviet Biocosmos 1887 in order to investigate the effects of cosmic rays. Artemia cysts and tobacco seeds were used in bulk or in monolayers sandwiched with track detectors. Biological and physical units were located outside and inside the spacecraft. Stacks included lead shielding in order to expose the objects to different doses of radiation. Total dosimetry was performed using thermoluminescent detectors. In spite of low levels of doses, the space flight resulted in a decrease in developmental capacity of Artemia cysts, and in a higher mutation rate in tobacco seeds. The more obvious responses occurred, in both cases, in biological objects exposed to the highest doses. These results are compared to those of previous space experiments.

Radiation-induced changes in late effects and in developmental capacities of exposed artemia cysts

Artemia dry cysts from a Californian bisexual strain used in several space experiments were irradiated with 60Co gamma rays. The three cyst populations experimented could be differentiated according to their development and survival rates. The variations observed for both of these criteria were related to the age of the cysts and the selection technique. The study of radiosensitivity based on LD50 value showed that the highest radiosensitivity differences were related to the cyst selection technique and not to the age. Furthermore, the three cyst populations showed that radio-induced lethal effects were enhanced, or appeared with time, namely following the delay between irradiation and the cyst development study. The observation of late effects after irradiations or after space flights show the difficulties encountered in assessing radiative risks during long duration space flights.

Changes in developmental capacity of artemia cyst and chromosomal aberrations in lettuce seeds flown aboard Salyut-7 (Biobloc III experiment)

This paper gives the results of investigations performed on the first container (A) of the Biobloc III experiment, flown aboard the orbital station Salyut 7 for 40 days. The space flight resulted in a decreased developmental capacity of Arterlia cysts, hit or not hit by the HZE particles. No effect was observed in cysts in bulk. A synergetic effect of microgravity and gamma pre irradiation is described. The germination of in-flight lettuce seeds was decreased. The space flight resulted also in a higher percentage of cells with chromosomal aberrations. Relations between biological response, TEL and location of HZE particles are discussed.

Radiosensibility of higher plant seeds after space flight

The influence of long-term storage of higher plant seeds under space flight conditions (49 to 827 days) on their radiosensibility was studied in the experiments on the orbital stations Salyut 6 and 7. Short-term storage has been proved to have no effect on radiosensitivity of Crepis capillaris seeds. Only in the case of maximal exposure duration the frequency of chromosome aberrations in post-flight irradiated seeds significantly exceeded the chromosome aberration frequency in the ground-based irradiated control. A statistically significant increase in the number of cells with multiple chromosome aberrations was also observed in this experiment. After gamma-irradiation of Arabidopsis thaliana seeds the germinating ability and survival rate of plants decreased depending on the duration of seed storage. Flight-exposed seeds were more sensitive to irradiations with respect to these parameters. A statistically significant increase in the frequency of recessive lethal mutations was observed only in two experiments of long exposure duration.

Experiments with air-dried seeds of Arabidopsis thaliana (L) Heynh. and Crepis capillaris (L) Wallr., aboard Salyut 6

Space flight factors resulted in the accumulation of genetic damage in embryonic meristem cells of seeds of Arabidopsis thaliana and Crepis capillaris in flights of different duration (49, 226, 408 and 827 days) aboard the orbital station Salyut 6. As a result, the viability of seeds and seedlings was reduced, and the sterility of plants grown from seeds exposed on Salyut 6 was increased. The effect depended upon the flight duration. The data obtained suggest an acceleration of seed aging under flight conditions.

Results on Artemia cysts, lettuce and tobacco seeds in the Biobloc 4 experiment flown aboard the Soviet Biosatellite Cosmos 1129

Artemia cysts, lettuce and tobacco seeds were flown aboard the Cosmos 1129 for 19 days. A correlative method was used in order to determine the passage of cosmic heavy ions (HZE particles) through the biological test objects. This space flight resulted in a decrease on hatchability, nucleic acid and protein synthesis in hydrated Artemia cysts. HZE particle effects on plant cellular chromosomes are confirmed. In tobacco seeds, a stimulating effect on germination rate and a higher frequency of abnormalities were observed. Dormant biological objects are a very suitable material to study cosmic ray effects: these objects can be arranged in monolayers and sandwiched between visual track detectors in order to determine the passage of the cosmic heavy ions (HZE particles). On the other hand this method allows us to study effects of microgravity and those of the protonic component of cosmic rays in the objects not hit by the HZE articles.

Genetic risks associated with radiation exposures during space flight

The genetic risks associated with manned space flight are judged to be of little significance to the general population. The risks may be significant to the irradiated individual, particularly if one focuses attention on the incidence of dominant and chromosomal mutations that are expressed in the first generation offspring. Even so, the risk is not increased to a great extent by the low linear energy transfer (LET) component of the space radiations. It is the presumed high LET component, neutrons especially, that would make the major contribution to the risk, because the relative biological effectiveness (RBE) values for this component, relative to low dose-rate photon irradiation, are between 10 and 40, depending upon the particular genetic effect and dose-rate comparison. The appropriate RBE value would probably be 20 or greater, so that even small neutron doses become magnified in their contribution. Under the assumed condition of protracted exposure to 8 rads of low LET radiation and 2 rads of high LET radiation, or from 48 to 88 rem, the individual's risk of transmitting a new dominant mutation that will be expressed in his immediate offspring is estimated to increase by at least 4% and as much as about 40%. The HZE-particle component is not expected to make a significant contribution to the total risk.

LET variation measurements behind different absorber thicknesses on COSMOS-1129 satellite

LET variation with the absorber thickness was measured by plastic detectors exposed on COSMOS-1129 satellite.

A review and comparative analysis of the biological damage induced during space flight by HZE particles and space hadrons

We have studied the somatic and genetic effects of heavy ions (HZE particles) and the very high energy hadrons of space radiation on various organisms ranging in complexity from bacteriophage to man. Experimental data were obtained in space, on high mountains and in a proton accelerator at energies of 76 GeV. In all these experiments local micro- and macroradiational damage was observed. This damage was characterized by severity over large local regions and for the most part was due to cascades of secondary particle bundles resulting from the collision of very high energy space hadrons with atomic nuclei rather than from cellular hits from relatively low energy single HZE particles. At present there does not appear to be any effective way to provide shielding against these cosmic hadrons.