Future Prospects - Genetics, Genomics and Breeding of Crop Plants - page 328

sunflower seeds can remain dormant for several years and then germinate
and grow years later. Dormant transgenic sunflower seeds would pose a
control problem if transgenic pollen is dispersed near populations of
nontransgenic cultivated or wild sunflower over a period of several years.
Bio-pharming of sunflower for drugs or medicines that are expensive to
synthesize and produce is a potentially lucrative enterprise. It is not likely
to occur in the US except under very rigid control situations. However, it
might be feasible and profitable in other countries or regions where wild
sunflower populations do not exist. Perhaps we can expect a new “quantum
leap” in sunflower production with the development of a technological tool
that allows the introduction of an agronomically favorable foreign gene
that is not expressed in pollen, which would minimize the possibility of
outcrossing with wild species to an acceptable risk. One potential technique
would be the introduction of foreign genes into sunflower chloroplast DNA
rather than nuclear DNA, as has been demonstrated in tobacco (Ruf et al.
2007; Svab and Maliga 2007). Each cellular chloroplast could act as a factory
for production of a pharmaceutical or nutriceutical. Because plant cells
possess many chloroplasts compared to only one nucleus, the efficiency of
product formation could be substantial over nuclear-transformed plants.
Of importance is the presence of foreign genes in the chloroplast rather than
the nucleus which would significantly reduce their integration into pollen
and minimize the risk of outcrossing with unintended species to a tolerable
level, thus allowing for commercial outdoor bio-pharming of valuable
proteins in North America with sunflower as the host plant.
10.5.3 Bioremediation
Sunflowers have the potential to assist in bioremediation of contaminated
soils. Two approaches have been reported in which sunflowers play an
important role: 1) utilization of sunflower oil to extract harmful chemicals,
and 2) planting of sunflower (phytoremediation) on soils contaminated
with heavy metals.
Gong et al. (2006) have reported that sunflower oil has a great capacity
to remove PAHs (polycyclic aromatic hydrocarbons) from contaminated
soils. Contaminated soils are transferred to a column and sunflower oil
allowed to percolate down through the soil. More than 90% of PAHs were
removed, with the treated soil retaining only 4-5% of readily biodegradable
sunflower oil.
The ability of sunflower to accumulate heavy metal ions such as
cadmium, chromium, zinc, mercury, and lead from the soil is well-known.
Li et al. (1997) described the genetic variation in cadmium accumulation by
sunflower genotypes, and Van der Lelie et al. (2001) have reported the use of
sunflower as a suitable crop for phytoremediation of soils polluted by zinc.