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Molecular Plant Breeding Provisional Publishing
Molecular Plant Breeding 2012, Vol.3, No.
6
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62
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59
Figure 6 Starch viscosities of the transgenic lines
Figure 7 Amylose contents (AC) test result in transgenic lines
that express
glg
B
The line of the DXY host was different from that of
the ZHB host in both starch viscosity and amylose
content. Starch viscosity in DXY host line was much
higher than that in ZHB host line. Amylose content in
DXY host line was significantly higher than the
control, but it was the same between ZHB host line
and control. Therefore,
glg
B expression in different
host genotypes led to various responses for starch
biosynthesis.
Data analysis showed that there was no significantly
correlation between starch viscosity and amylose
contents of the transgenic lines. There wasn’t any
correlation between amount of RT-PCR products and
starch viscosity, either. Difference in starch viscosities
between two genotypes host lines and the controls
indicates that
glg
B expression within potato regulates
starch biosynthesis through increasing amylopectin
synthesis. This result is in accordance with results
obtained when
glg
B is expressed in
amf
potato done
by Anne et al (1996). Meanwhile, effect of
glg
B
expression in potato on amylose biosynthesis shows
genotype specificity.
2 Discussions
In this study, we transformed
glg
B into two potato
cultivars. Two
glg
B -expressing transgenic groups
were obtained. Starch viscosity and amylose content
in starches isolated from the two groups were assayed.
Data analysis of the assay indicated that two
genotypes performed differently in response to
glg
B
expression. This is the first evidence to show crop
genotype-specific response to an extraneous gene
expression. This means that more than one crop
genotypes have to be taken into consideration when a
transgenic breeding program is made to improve
starch quality of the crop.
In addition, in this study, we found that starch
viscosities of all transgenic lines were significantly
higher than that in the control, one genotype
expressing
glg
B showed much higher starch viscosity
than the other genotype expressing
glg
B. This
finding indicates clearly that starch feature can be
modified in wider extent than expected through
expression of extraneous genes involved in
polysaccharide biosynthesis. Plant starch feature
could be subjected to not only endogenesis genes
but also extraneous relatives.
Many factors could affect the expression of a target
gene transformed into a plant species, such as the
location of insertion in host genome, completeness of
gene inserted, copy number etc; however, alteration of
gene expression involving starch biosynthesis, such as
starch branch enzyme is a way to find how starch
biosynthesis is regulated. It is particularly important
for polyploidy starch plant, such as potato; However,