The examples above represent the insertion and expression of a single or very few
genes. Because most phenotypic traits are polygenic, i.e., involving more than one gene,
successful engineering will require manipulation of a network of complex metabolic and
regulatory pathways involving multiple genes and/or gene families (Chen et al. 1998).
One can envision a combination of breeding and transgenic technology to allow large-
scale manipulation of the genome to modulate such complex traits.
As our understanding of biological processes in cells and organisms improves, and as
plant transformation techniques evolve, we will be able to more efficiently and rationally
create new plants for space exploration.
9.5 Nanotechnology
Nanotechnology encompasses the development of tools and devices for the manipulation
and probing of matter of nanometer-scale dimensions. Recently, the potential of
nanoscience and its tools have become clear. A great deal of effort is being expended to
develop nanosensors and nanotools.
It is entirely possible that such tiny machines will be engineered and inserted into liv-
ing cells. It is clear that within the foreseeable future we will develop new tools that will
be important for space exploration. A critical barrier that must be overcome is the devel-
opment of nanoscale devices that can be implanted into living cells or (preferably) pro-
duced in vivo by co-opting the cellular machinery itself. Recently, a gene from the hy-
perthermophile Sulfobolus shibataewas altered to produce a protein that adheres to
gold or to semiconductor material (McMillan et al. 2002). These two-dimensional, self-
assembled lattice structures could act as nano-templates upon which sensors or other de-
vices could be built. Actuators to enable gene expression could be created, and sensors to
monitor gene expression at all levels could be developed. Although linking these
nanosensors and nanoactuators to external (electronic) devices will be a significant chal-
lenge, it is possible.
9.6 Sensors, biosensors, and intelligent machines
Precise monitoring and control of all aspects of the human/plant/environment biosphere
must be a basic system component of a bioregenerative life support system for human life
support in space. The integration of nanobiosensors that are linked telemetrically to Earth
as part of a distributed intelligent system will be key to success. Because any program of
solar system exploration will involve significant periods with humans not present or un-
available to spend time on plant culture, the integration of remotely controlled and smart
nanotechnology to monitor and control plant function and metabolism of plants will be
critical.
The distributed sensor system must have versatility and adaptability, and be able to
monitor both the physiological status of the plants as well as the environment in which
they are growing, including the aerial environment and the rhizosphere. Microfabrication