Cellular Mechanisms of Space Flight-Specific Stress to Plants (BRIC)

Objectives

Plant development includes orderly processes of cellular activities that are dependent on time and the dimensional space available to the cells. Previous studies have shown that microgravity has an adverse effect on plant cell development and function. These previous studies have shown that while plant cell growth in space occurs, it is slower than normal and fewer cells grow to maturity. Some of the studies done on previous Shuttle flights indicated chromosomal or genetic abnormalities occur to plants during space flight. Investigators hypothesize that this is a result of the way plants experience stress that is specific to space flight, such as microgravity and radiation.

The objectives of this experiment were to prove that protection from water stress will allow adaptation and normal cell division and development in prolonged microgravity; to prove that water stress will have serious negative effects on cell division and development if additional "mismatches" are imposed; to validate whether previously encountered chromosomal rearrangements are a result of adaptation to space stress; to determine whether any effect of microgravity on gene transcription can be found and whether the responses of cells to space can be distinguished from other stress reactions; and to verify that space stress is a distinct kind of stress with an asssociated specific altered gene expression.

Shuttle-Mir Missions
NASA-4

Approach
Embryologically competent daylily (Hemerocallis cultivar. Autumn Blaze) cell cultures were prepared using standard, 100 mm petri plates. Four each of these petri plates were loaded into BRIC-VC canisters, and nine canisters were flown for a total of 36 petri plates. BRIC canisters are metal containers that hold passive experiments requiring little or no crew interaction. Temperature and relative humidity data loggers were placed in six of the nine canisters and all canisters were flushed thouroughly with a 5% carbon dioxide gas after being sealed. A similar set of canisters was prepared at Kennedy Space Center and stowed in the controlled storage to serve as a ground control. In addition, the principal investigator prepared nine canisters and maintained them at his home laboratory.

After return to Earth, gas samples were collected in gas sampling syringes and gas sampling bags from the flight and ground BRIC canisters. The flight samples were hand carried in a temperature monitored "igloo-type" cooler to the principal investigator in New York for analysis.

Results
Poor growth and nuclear abnormalities observed in some space-grown plants were thought to be caused by a combination of factors, including biological status, the specific way they were grown and the way they experienced multiple stresses, some of which are space-specific. Data from a 132-day experiment on Mir using embryogenic daylily cell cultures allowed the researchers to harmonize seemingly contradictory evidence - a) the more developed an embryo the less likely it is to suffer catastrophic cell stress during growth; the less developed, the greater its vulnerability; (b) the extent to which the stress becomes manifested is also dependent on the extent of pre-existing stresses imposed by suboptimal growing conditions; (c) an appropriate albeit undesirable "stress match" with other non-equilibrium determinants, much like a "tug of war", can result in genomic variations in space.

In conclusion, fastidiously controlled growing environments for plant cells must be devised if one is to resolve the matter of direct versus indirect effects of space. Access to 1-G centrifuges must be an important parameter in these experiments. On a practical level, it is predicted that adapting plant biotechnologies to space conditions will not be a casual matter.

Earth Benefits
The concept of stress being pivotal to early events and the progression of somatic embryogenesis as being stress-susceptible is novel and offers a unifying concept for cell culture strategies as they relate to the study of differentiaion and development. The concept of stress being manifested as chromosomal damage is likewise novel, certainly in plants. Aside from its intrinsic value for basic understanding, the research performed is critical to the many applied research projects being carried out throughout the "plant biotechnology world". These range from improving responses from in vitro systems and streamlining protocols, to generating and selecting genetically uniform populations for use in clonal multiplication and genetic selection strategies.

Publications
Krikorian, A. D. (1997) Plant cells in space: what have we learned? Gravitational and Space Biology Bulletin 11 (no. 1): 3.

Krikorian, A. D. (1998) Plants and Somatic Embryos in Space: What Have We Learned? American Society for Gravitational and Space Biology Bulletin 11(no.2): 5-14.

Levine, H. G., Anderson, K. F. and Krikorian, A. D. (1998) Characterization of the physical environment within BRIC-100VC canisters flown on 'Mir' with embryogenic daylily cell cultures. In: 32nd Scientific Assembly of COSPAR 12-19 July 1998. Nagoya, Japan. p. 449.

Levine, H. G., Anderson, K. F. and Krikorian, A. D. (199?) The 'gaseous' environment in sealed BRIC-100VC canisters flown on 'Mir' with embryogenic daylily cell cultures. 32nd COSPAR Scientific Assembly (Nagoya, Japan) (accepted).

Krikorian, A. D. 1998. Plant somatic embryos in space. In: 32nd Scientific Assembly of COSPAR 12-19 July 1998. Nagoya, Japan. p. 380.

Krikorian, A. D. 1998. Somatic embryos of daylily in space. In: 32nd COSPAR Scientific Assembly (Nagoya, Japan) (accepted).

Principal Investigators
Abraham D. Krikorian
State University of New York at Stony Brook

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