7.4.5 Vectors Derived from Plant Sequences
The revolutionary advances in recombinant DNA technology provide great opportunities to
engineer new traits in crop plants that could not have been achieved through conventional
breeding. Ironically, it is this ability to overcome species barriers, to widen the pool of
genetic traits available for crop modification, that makes this technology extremely power-
ful, while at the same time being the cause of many objections to the deployment and con-
sumption of genetically modified crop varieties. Consumer surveys have identified that
public acceptance of genetically engineered organisms is linked to concerns about the
origin of the genetic material used to improve crop traits. These surveys have identified
that the food crops least appealing to consumers are those containing foreign genetic
material derived from organisms distantly related to plants. Ironically, wild-type plant
cells already contain the genetic material of three genomes, the plant nuclear genome,
and two bacterially derived genomes: the chloroplast and the mitochondrial genomes,
from cyanobacteria anda-proteobacteria, respectively. Some concerns could be alleviated
through the careful design of the recombinant DNA vectors used to improve crop varieties.
During the design stage of vector construction, measures can be taken to ensure that
Figure 7.19.Multisite Gatewaywallows several DNA fragments to be cloned within a single vector
construct. More recent advances in the design of newattrecombination sites have permitted the
assembly of up to five DNA molecules within a single vector construct, but none have been designed
as yet for plant transformation.
7.4. VECTOR DESIGN 181