The contribution of bnnrt1 and bnnrt2 to nitrate accumulation varied according to genotypes in Chinese cabbage
Two Chinese cabbage cultivars (SYM and HGQGC) with significant difference in nitrate accumulation were used in the experiment by real-time PCR technique. The expression level of BnNRT1 and BnNRT2, nitrate uptake rate and nitrate reductase activity (NRA) were detected under 0.2 mM and 2 mM NO3- treatments. The results showed that the nitrate accumulation in Chinese cabbage varied according to genotype, and high accumulator SYM got significant higher nitrate concentration and nitrate uptake rate than low accumulator HGQGC. The difference between cultivars became more obvious with high nitrate in growing medium especially in root; and the SYM was more sensitive to nitrate enhancement in growing medium than HGQGC. The different expression pattern of BnNRT1 and BnNRT2 may partly explain the different nitrate concentration between SYM and HGQGC. Under 2 mM nitrate treatment, BnNRT2 may be the key factor resulting in higher nitrate concentration and higher nitrate uptake rate, in SYM than HGQGC. The higher nitrate accumulator SYM posses higher NRA than HGQGC, which means stronger ability to assimilate absorbed nitrate in SYM than the low accumulator, HGQGC.
Key words: Chinese cabbage, NRT, nitrate-transporter, genotypes-difference.