Starch degradation are affected in OEmiR399 transgenic
Arabidopsis plants under freezing stress
The soluble sugar contents of Arabidopsis llines were analysed. The
results showed that at low temperature, the soluble sugar contents of
OEmiR399 transgenic Arabidopsis plants were markedly higher than that of
WT (Fig. 9A). The results of
starch contents showed that at low temperature, the starch contents of
OEmiR399 transgenic Arabidopsis plants were significantly lower than
that of WT(Fig. 9B). These findings implied that the higher soluble
sugar contents in OEmiR399 transgenic Arabidopsis plants were
accumulated through degrading starch. To further validated tae-miR399
fuction on starch degradation under freezing stress, we detected the
amylase activities in Arabidopsis lines. The results showed that
α-amylase activity of OEmiR399 transgenic Arabidopsis plants was only
higher than that of WT at 4℃ (Fig. 10A). Meanwhile, not only β-amylase
activity of OEmiR399 transgenic Arabidopsis plants was higher than that
of WT at 4℃, but also significantly higher than that of WT at -10℃ (Fig.
10B). The expressions of genes encoding α-amylase (AtAPL1 andAtAPL3 ) and β-amylase (AtBAM1 and AtBAM3 ) were also
detected, the results showed that low temperature observably induced the
expression of amylase genes in all Arabidopsis lines (Fig. 10C, D, E and
F). However, not all of these amylase genes were affected by
overexpression of tae-miR399. Before cold treatment, only the expression
of AtAPL1 in OEmiR399 transgenic Arabidopsis plants was higher
than that in WT(Fig. 10C). At 4℃,the expressions of all amylase genes in
OEmiR399 transgenic Arabidopsis plants were higher than that of WT with
variety degrees (Fig. 10). At
-10℃, only the expression of AtBAM3 in OEmiR399 transgenic
Arabidopsis was higher than that in WT, while the expressions ofAtAPL1 and AtBAM1 slightly lower than that of WT (Fig.
10C, E and F). To explore whether GWD in OEmiR399 transgenic Arabidopsis
also regulates starch metabolism under freezing stress, we detected the
expression of its coding genes AtSEX1 and AtSEX4 in
Arabidopsis lines. The results showed that under low temperature stress,
the expression of AtSEX1 in all Arabidopsis lines was not induced
(Fig. 10G). And there was no significant difference in the expression
level of AtSEX1 among all Arabidopsis lines (Fig. 10G). The
expression of AtSEX4 was different from that of AtSEX1 . At
low temperature, the expression of AtSEX4 in all Arabidopsis
lines was significantly up-regulated (Fig. 10H). And at 24°C and 4°C,
the expression of AtSEX4 in OEmiR399 transgenic Arabidopsis
plants was significantly higher than that in WT(Fig. 10H). However, at
-10°C, there was no significant difference in the expression level ofAtSEX4 between WT and OEmiR399 lines(Fig. 10H).