Isolation and characterization of a high-affinity ammonium transporter ApAMT1;1 in alligatorweed
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In aquatic fields, ammonium (NH4+) is the most preferred nitrogen (N) source used by plants. The uptake of NH4+ is facilitated by the family of ammonium transporters (AMTs). However, the molecular functions of AMTs in aquatic plants are largely unknown. In this work, a new NH4+ transporter encoding gene, ApAMT1;1, was isolated from the typical aquatic plant alligatorweed, using degenerated primers and rapid amplification of cDNA end (RACE) techniques. Quantitative real time PCR showed that ApAMT1;1 was predominantly expressed in roots, and significantly induced by NH4+ starvation in all tested tissues, including leaves, stems and roots. Functional determination and 15N-labeled ammonium uptake assays in yeast cells indicated that ApAMT1;1 was a typical high-affinity transporter, with a 38.6 μM Km value, and the phosphorylation site T469 was required to retain its NH4+ uptake capacity. Further analyses with Met sulfoximine (MSX), a NH4+ assimilation inhibitor, demonstrated that ApAMT1;1-mediated NH4+ uptake might be feedback regulated by the internal NH4+ accumulation. Our results reveal a functional role of ApAMT1;1 in the uptake and transport of NH4+ in aquatic plants.
KeywordsAlligatorweed Ammonium transporter ApAMT1;1 Aquatic plant NH4+ uptake
We are grateful for Dr. Julia Davies and Dr. Elsa Matthus (Department of Plant Science, University of Cambridge) for critical comments on this work and sincere help during the studies in University of Cambridge.
This work was financially supported by grants from the National Natural Science Foundations of China (Grant Nos. 31601819, 31700524 and 31801837), Doctoral Fund of Shandong Natural Science Foundation (Grant Nos. ZR2016CB19 and ZR2016CB48), Science and Technology Project of Yantai (Grant No. 2016ZH058), Key R&D Program of Shandong Province (Grant No. 2017NC210012), and The Modern Agricultural Industry Technology System Innovation Team of Shandong Province of China (Grant No. SDAIT-02-05).
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Conflict of interest
We declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted.
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