this type of system will depend on advances in genomics, proteomics, bioinformatics,
and nanoscience at a minimum. Understanding and harnessing the biochemical machin-
ery of plant cells to produce said devices in situ will be critical, as will the identification
of technology areas that currently limit such processes.
The foundational work upon which this scenario can be built has been done. The phys-
iology and metabolism in a variety of space-exposed plants have been studied (Tripathy
et al. 1996; Croxdale et al. 1997; Musgrave et al. 1998; Klymchuk et al. 2001; Kuznetsov
et al. 2001; Nedukha et al. 2001; Stutte et al. 2006). Extremely early molecular responses
to gravitational and mechanical stress have been identified (Kimbrough et al. 2004).
Research on molecular aspects of plant stress gene regulation in space-grown plants (Paul
et al. 2001; Stankovic 2001) as well as developing chimeric genes for use as biomonitors
(Paul and Ferl 2002) has been published. Localized stimuli resulting in systemic regula-
tion of gene expression in plants has been shown, using heat pulses (Stankovic and
Davies 1996; Stankovic et al. 2000), electrical stimulation (Stankovic and Davies 1996;
Davies and Stankovic 2006), and low-level microwave radiation (Vian et al. 2006).
Recently, the groups of Boss and Grunden expressed archaebacterial genes from
Pyrococcus furiosusinArabidopsiscells, resulting in increased survival rate under high
temperature (Im et al. 2005). Identification and expression of genes from extremophiles
have the potential of generating plants that could survive conditions beyond their adap-
tive range here on Earth. Finally, Wheeler and his colleagues have published extensively
on advanced life support concepts and on the development of a Martian greenhouse
(Wheeler 1999).
A sensible progression and melding of this foundational work and inclusion of other
critical enabling technologies is laid out in the architecture in Figure 9.2, and demon-
strates a pathway toward “programmable plants” for human life support in space.
As of this writing, technology limitations exist in the scale of plant transformation and
in the ability to communicate specific programming instructions to plants. Current ge-
netic engineering technology allows relatively simple transformations of a few genes at a
time. Although this can be powerful when artfully employed to modify metabolic path-
ways, in order to have ever-increasing influence we must move from making one or two
modifications at a time to making sweeping changes in plant structure and function. The
time may be nearing when we can engineer and introduce minichromosomes into plants,
which are capable of carrying stably, from generation to generation, batteries of genes en-
coding new biochemical pathways.
Current human–plant communication technologies allow relatively simple signal trans-
missions to plants, usually through modification of the environment. Modifying light cy-
cles can, for example, induce flowering, and modification of nutrition can evoke changes
in plant form. However, true plant programmability necessitates the development of novel
signaling methods that will allow plants to respond to various and specific signals that
might be transmitted across interplanetary space. Such a programmable plant needs to re-
spond to remotely applied stimuli in a reversible manner. To provide specificity, the sig-
nals applied need to be distinct from the environmental stimuli that plants normally expe-
rience. Transduction of the physical stimuli into biological responses will be accomplished
through introduction of stimulus-responsive specific molecular switches.
In the long term, success of human exploration of space will depend on the ability of
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