production of wax esters in crambe

The above issues can be solved by using a marker-free selection strategy. Several
alternatives exist such as the Cre/Lox system (Corneille et al., 2001), using a
transiently cointegrated selection gene (Klaus et al., 2004) or combining an
inducible site-specific recombinase for the precise elimination of undesired,
introduced DNA sequences with a bifunctional selectable marker gene used for the
initial positive selection of transgenic tissue and subsequent negative selection for
fully marker-free plants (Schaart et al., 2004).
4.2.2 Risk mitigation of GM
To minimise risks in using a genetic engineering strategy for the production of wax
esters, this report suggests certain steps.
To reduce the risks of mixing an industrial feedstock into the food chain, establishing
this production in a non-food crop is regarded as the preferred strategy. It is not
expected that Crambe can cross easily with other related species. Inter-specific
crosses between the most closely related species C. hispanica and C. abyssinica
gave nearly sterile offspring, associated with imbalances in chromosome number
(Wang and Peng, 1998). Outcrossing of a GM Crambe with wild Crambe species
and/or other crucifereae species is therefore unlikely. However, when growing the
GM Crambe it is recommended to use the same cultivation practices as when
growing GM rapeseed, e.g. non-GM barrier crop, minimum distance to nearby non-
GM Crambe field and prevention of volunteer GM-Crambe by tillage and/or
herbicide treatment the following season should be utilised to help ensure identity
preservation of the crop.
Considering the types of wax esters and fatty acids that will be produced in the GM
Crambe, i.e. novel branched fatty acids and hydroxyl fatty acids in waxes, it should
be noted that the same or similar compound already exists in nature. For example
hydroxy fatty acids are produced in seed oils of castor bean and Lesquerella sp.
(van de Loo et al., 1995; Broun, et al., 1998) while wax esters containing branched
fatty acids are found in the fluids that certain birds use to impregnate their feathers
(Kolattukudy et al., 1985).
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