| Abstrakt: |
Nitrate is a major source of nitrogen, yet little is known about the molecular and regulatory mechanisms of nitrate transport in woody plants. In this study, three full-length nitrate transporter genes (MhNRT1.5, MhNRT2.1, and MhNRT2.5) were cloned from "pingyitiancha" (Malus hupenensis Rehd. var. pinyiensis Jiang). The putative amino acid sequences of MhNRT2.1 and MhNRT2.5 were closely-related to the predicted amino acid sequences of the products of the apple genes MDP0000239537 (98.9% sequence identity) and MDP0000266497 (98.6% sequence identity), respectively. No predicted amino acid sequence of the apple genes was closely-related to MhNRT1.5. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis revealed that all three genes were expressed in roots, stems, and leaves. Expression of these three genes was induced over a wide range of nitrate concentrations (0.5 - 10 mM). The patterns of expression of MhNRT1.5, MhNRT2.1, and MhNRT2.5 suggested that they may belong to the inducible nitrate transporter gene family. NO3- ion concentrations in MhNRT1.5 and MhNRT2.1 transgenic leaves of Arabidopsis thaliana were higher than in non-transformed leaves of A. thaliana. The average numbers of siliques in the first 10 cm (counted acropetally) were also higher than in non-transformed A. thaliana. Our results demonstrate that expression of the MhNRT1.5 and MhNRT2.1 genes regulates NO3- ion concentrations, while MhNRT1.5 regulates the development of inflorescences. [ABSTRACT FROM AUTHOR] |
