Interference 103,579
inhibition: cDNA versus genomic DNA” (VDX 4, p. 752, col. 1),
Kuipers’ 1995 publication discloses (emphasis added):
The origin of the GBSS sequence was shown to be an
important factor in determining the efficacy of antisense
inhibition. The full-length GBSS cDNA (pGB50, pKGBA50)
and genomic DNA (pGBA10, pKGBA10) constructs were all
found to be capable of complete inhibition of GBSS gene
expression, but it was shown that the antisense GBSS cDNA
constructs resulted in complete inhibition of GBSS gene
expression in a higher percentage of transgenic potato
clones (Table 1). This was also observed for the partial
cDNA construct pKGBA55 as compared to the corresponding
partial genomic construct pKGB25. The percentage of
clones with inhibited GBSS gene expression was shown to
be higher for the antisense GBSS cDNA constructs than for
the genomic DNA constructs (Fig. 2A). The presence of
intron sequences in the genomic constructs might contribute
to the observed differences in antisense inhibition. The
full length GBSS gene contains 12 introns (van der Leij
et al. 1991), four of which are also present in the gene
fragment used for pKGBA25. These introns will not be
processed when present in antisense orientation. . . .
The supposed . . . can be explained by the differences in
the GC content, which is 42.7% for exon (cDNA) sequences
and 33% for intron sequences. . . . In this way, the
presence of intron sequences with a low GC content might
reduce the efficacy of antisense inhibition of gene
expression.
In its discussion, “Effect of construct composition on
antisense inhibition: full-length versus partial genomic DNA”
(VDX 4, p. 752, col. 2; emphasis added), Kuipers’ 1995
publication discloses:
In transgenic clones, the degree of inhibition of GBSS
gene expression was found to vary for the genomic GBSS
antisense constructs. However, similar frequencies of
complete and incomplete inhibition could be achieved
with pGBA10, pKGBA10 and pKGBA31 (comprising 0.6kb of
the 3' end of the GBSS coding region and containing one
intron sequence). This indicates that the size of the
antisense RNA does not affect the efficacy of inhibition.
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