Seedlings and cell cultures both engage gene expression changes to alter metabolic responses to the spaceflight environment, but they engage dramatically different responses. This response differential between seedlings and cell cultures could be as simple as a consequence of examining a very uniformly responding system in undifferentiated cells compared to a complex organism composed of differentiated organs and tissues. Or, it could be as complex of the presence of an organ-specific feedback sense and response system that allows seedlings, but not undifferentiated cells, to more properly sense the environment and integrate a response that makes sense based on input from organ systems. Regardless, it clear that even undifferentiated plant cells sense spaceflight as an environment that demands molecular responses. Many of those responses tap familiar pathways - auxin, calcium signaling, stress – and there is a tendency to place those responses into familiar earth-based context. But given the truly novel nature of spaceflight, responses may propagate in ways that are distinct from well-defined terrestrial analogs.
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