摘要
This paper reports the cloning and expression analysis of a high-affinity nitrate transporter inwheat ( Triticurn aestivurn L.). A full-length cDNA, TaNRT2.3(accession number AY053452), was isolatedfrom NO3--induced roots of wheat. The cDNA encodes a polypeptide with 507 amino acids and 12transmembrane domains, belongs to nitrate/nitrite porter (NNP) family within the major facilitator superfamily(MFS), and is closely related to other NRT2 proteins from plants. The expressions of TaNtTT2 genes inwheat tissues were analyzed using Northern blot, results indicated that TaNRT2 were induced specificallyin roots but not in shoots in response to both low (5-200 μmol/L) and high (2.0 retool/L) concentrationsof NO^-. TaNRT2transcripts were undetectable in N-deprived or NH4^+grown plant roots. The significantcorrelation between the time course of TaNtTT2transcription accumulation in the roots of wheat plantsgrown in 0.2 mmol/L NO3- and the time course of the nitrate uptake rates by wheat plants grown under thesame conditions suggested that TaNtTT2 played an important role in high-affinity NO3-uptake. Using thesplit root system, we found that supplying NO3- to one part of the roots induced the expression of TaNtTT2in the other part not supplied with NO3- or supplied with NH4^+, which implied that N cycling within plantsacted as a regulatory signal for N uptake.
