Abstract
Ammonium (NH4+) plays key roles in plant growth, development, fruit quality, and yield. In plants, NH4+ uptake and transport are facilitated by NH4+ transporters (AMT). However, molecular mechanisms and physiological functions of type-II AMT (AMT2) transporters in fruit trees are still unclear, especially in peach. In this study, we cloned and characterized an AMT2 family gene from peach, PpeAMT3;4, and determined its function in yeast mutant. Expression analysis showed that PpeAMT3;4 was majorly expressed in peach roots and significantly decreased by NH4+ excess but had no response to NH4+ deficiency. Functional determination and 15nitrogen-labeled NH4+ uptake assay in yeast cells implied that PpeAMT3;4 was a typical high-affinity transporter, with a Km value of 86.3 μM, that can uptake external NH4+ in yeast cells. This study provides gene resources to uncover the biological function of AMT2 transporters and reveals molecular basis for NH4+ uptake and nitrogen (N) nutrition mechanisms in fruit trees.
Highlights
Ammonium (NH4+) is the preferred form of nitrogen (N) source absorbed by both annual and perennial plant species, especially in N-deficient soils [1, 2]
Coding sequence (CDS) of the PpeAMT3;4 gene was downloaded from the database, and the first bp sequence from the ATG codon and the last bp sequence from the TAA codon were chosen as the forward primer and reverse primer, respectively (Table 1)
To confirm the evolutionary relationships of PpeAMT proteins, a maximum likelihood (ML) phylogenetic tree was generated based on the alignment of the amino acid sequences of PpeAMT proteins
Summary
Ammonium (NH4+) is the preferred form of nitrogen (N) source absorbed by both annual and perennial plant species, especially in N-deficient soils [1, 2]. With the increasing soil N input and atmospheric deposition, plants have to deal with NH4+ stress from the ground [1,2,3,4,5,6]. An optimal sources below and above amount of NH4+ should be effectively absorbed from the soil via plant roots, to sustain basic growth demands. Extensive studies in angiosperms [3,4,5] and in basal land and plant uptake lwiveerrewopretrfo[6rm] einddbicyatNedH4th+attraNnsHp4o+rtearcsqu(AisiMtioTn) through the plasma membrane of root cells. AMT family gene was observed in Arabidopsis [7], and In Arabidopsis, the phosphorylation of the threonine (Thr) residue in the C-terminal tail region of AtAMT1.1 (Thr460), AtAMT1.2 (Thr472), and AtAMT1.3
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