4.6. Gene expression analysis
The expression pattern of SlNPF6.3 (formerly, NRT1.1), two NRT2
family member genes (SlNRT2.1 and SlNTR2.3), together with
partner SlNAR2.1 in tomato roots exposed to 0.1 or 5 mM NO3
was
investigated by RT-PCR. The expression of SlNPF6.3 was very low
and no significant change was detected under our experimental
conditions in both genotypes (data not shown). Expression of the
two component high affinity uptake system, SlNRT2.1/NAR2.1 was
significantly higher in UC82 when compared with RO at low NO3
supply (Fig. 7AeB). At 5 mM NO3
supply, SlNRT2.1 expression did
not show any significant difference between genotypes, but
SlNAR2.1 expression was significantly higher (59%) in RO. At low
NO3
supply, SlNRT2.3 expression was significantly greater (82%) in
RO than UC82 (Fig. 7C). When grown in 5 mM there much lower
expression and this was similar for both genotypes.
The level of NR transcript was investigated by RT-PCR in tomato
roots and shoots grown in 0.1 or 5 mM NO3
. NR expressionwas not
significantly different in roots of both genotypes at low NO3
supply,
while it was significantly higher (72%) in UC82 compared to RO at
5 mM NO3
(Fig. 7D). At low NO3
supply, significant differences
were observed in shoots between genotypes, with higher NR
expression in RO compared to UC (Fig. 7E). The shoot NR expression
was not significantly different between genotypes growing in 5mM
NO3
(Fig. 7E).