Cloning and Functional Determination of Ammonium Transporter PpeAMT3;4 in Peach

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 K 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.