7.4 Vector Design
Recombinant DNA technology has made an enormous impact on plant biotechnology, both
in the development of novel crop traits and the functional analysis of new genes and their
promoters. The efficient functional analysis of DNA fragments and the effective application
of the resulting discoveries to crop trait improvement are increasingly dependent on inno-
vative vector design and construction. The design and construction of vectors has an impact
on the versatility of experimental systems and influences the public acceptability of geneti-
cally modified crops.
7.4.1 Vectors for High-Throughput Functional Analysis
Obtaining nearly the entire genomic DNA sequence of the model plant organisms, rice
(Oryza satica), a monocot, and arabidopsis (Arabidopsis thaliana), a dicot, have presented
Figure 7.16.The pUNI vector contains a conditional origin of replication that functions only in
E. colistrains that express thepirgene (which encodes an essential replication protein,p) and an anti-
biotic selectable marker. The pHOST vector contains the ColE1 origin of replication and an alternative
antibiotic selectable marker. Nonrecombinant vectors are counterselected: the pUNI vector, by a host
bacterial strain that does not express thepirgene; and the pHOST vector, by media containing the
antibiotic used to select the pUNI vector. Using this dual selection system, only bacteria containing
the recombined, or cointegrated, molecule survive.
7.4. VECTOR DESIGN 177