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Plant Sci. 2017 Nov;264:102-111. doi: 10.1016/j.plantsci.2017.09.001. Epub 2017 Sep 12.

Molecular identification of tobacco NtAMT1.3 that mediated ammonium root-influx with high affinity and improved plant growth on ammonium when overexpressed in Arabidopsis and tobacco.

Author information

1
Department of Plant Nutrition, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China; Institute of Tobacco Science Research of Chongqing Tobacco Company, China Tobacco Corporation, Chongqing 400716, China.
2
Department of Plant Nutrition, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China.
3
Department of Plant Nutrition, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China; College of Agriculture Sciences, Hunan Agricultural University, Changsha 410128, China.
4
Institute of Tobacco Science Research of Chongqing Tobacco Company, China Tobacco Corporation, Chongqing 400716, China.
5
Department of Plant Nutrition, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China. Electronic address: LL1025@cau.edu.cn.

Abstract

Although biological functions of ammonium (NH4+) transporters (AMTs) have been intensively studied in many plant species, little is known about molecular bases responsible for NH4+ movement in tobacco. Here, we reported the identification and functional characterization of a putative NH4+ transporter NtAMT1.3 from tobacco (Nicotiana tabacum). Analysis in silico showed that NtAMT1.3 encoded an integral membrane protein containing 464 amino acid residues and exhibiting 10 predicted transmembrane α-helices. Heterologous functionality study demonstrated that NtAMT1.3 expression facilitated NH4+ entry across plasma membrane of NH4+-uptake defective yeast and Arabidopsis qko mutant, allowing a restored growth of both yeast and Arabidopsis mutant on low NH4+. qPCR assay revealed that NtAMT1.3 was expressed in both roots and leaves and significantly up-regulated by nitrogen starvation and resupply of its putative substrate NH4+ and even nitrate, suggesting that NtAMT1.3 should represent a nitrogen-responsive gene. Critically, constitutive overexpression of NtAMT1.3 in tobacco per se improved obviously the growth of transgenic plants on NH4+ and enhanced leaf nitrogen (15% more) accumulation, consistent with observation of 35% more NH4+ uptake by the roots of transgenic lines in 20min root-influx test. Together with data showing its plasma membrane localization and saturated transport nature with Km of about 50μM for NH4+, we suggest that NtAMT1.3 acts an active NH4+ transporter that plays a significant role in NH4+ acquisition and utilization in tobacco.

KEYWORDS:

Active ammonium transporter; Ammonium uptake; Arabidopsis qko-mutant; Nitrogen use; Overexpression; Tobacco; Yeast complementation

PMID:
28969790
DOI:
10.1016/j.plantsci.2017.09.001
[Indexed for MEDLINE]

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