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 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