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Protein Expression in Glycine max Cells under Microgravity Conditions.  W.A. Kelly Jr., S.E. Kelly, and J.V. Valluri.  Division of Biological Sciences, Marshall Univ., Huntington, WV.

   Life support systems involving plant based protein production are likely to play an important role in long-term space missions. Higher plants can be used for production of food and oxygen, water purification, and carbon dioxide removal. This is resource intensive and many details need refinement before higher plants can be reliably grown in space. However, the environment maintenance requirements for higher plants in undifferentiated cell suspension form is significantly less demanding than supporting plants in a controlled chamber environment. The recent development of the gravity independent Hydrodynamic Focusing Bioreactor (HFB) by NASA, presents a significant opportunity to advance the application of plant cell culture technology as a valuable component of advanced life support systems for space exploration.  The HFB provides a unique hydrofocusing capability that simultaneously enables a low-shear culture environment and a unique hydrofocusing-based suspension of cells and tissue aggregates.   The 3-D in vitro growth, biomass and protein production from Soybean (Glycine max) cell cultures was investigated under microgravity. Morphometric analysis of fixed samples demonstrated that 3-5 day old cells under microgravity conditions were significantly larger than control soy bean cells kept at l-g. Confocal microscopy analysis showed that cells exposed to microgravity conditions for 3 days had larger vacuoles and slightly reduced starch content compared to control cells. Cell aggregates formed under microgravity conditions had an average of 8-12 cells per aggregate with two-fold increase in biomass in 3 days. Biochemical analysis indicated that the microgravity samples displayed a reduced packed cell volume, an increased concentration of soluble proteins per cell, and a reduced specific activity of peroxidase in the cytoplasm.   Total soluble proteins from soy cells under microgravity were analyzed by SDS -PAGE analysis. The resulting protein patterns showed varying differences in total protein expression and in active protein synthesis between microgravity and 1-g control cells.

(Supported by a grant from the WV Space Grant Consortium.)