VcAMT14 Enhances Ammonium Uptake in Blueberries During Mycorrhizal Symbiosis

Ammonium (NH₄ ⁺) is a crucial nitrogen (N) form for plant growth. The functions of ammonium transporters (AMTs) in mycorrhizal plants and their role in mediating ammonium uptake and regulating N metabolism in blueberry are not fully understood. In this study, 19 VcAMT genes were identified in blueberry. Tissue-specific expression analysis revealed that nine VcAMT members exhibited root-predominant expression patterns, with significant upregulation following inoculation with the O. maius BL01. Notably, VcAMT14 was specifically upregulated during mycorrhizal symbiosis and under N regulation, and subcellular localisation analysis confirmed its protein is located at the plasma membrane. Functional analysis in yeast demonstrated that VcAMT14 mediates NH₄⁺ transport activity. Furthermore, inoculation with O. maius BL01 enhanced rhizosphere soil sucrase activity, soil urease activity, soil phosphatase activity, N content, GS/GOGAT enzyme activity, and the expression levels of related genes in blueberry plants, while simultaneously reducing soil pH. Conversely, VcAMT14 silencing resulted in significantly reduced NH₄⁺ content, GS/GOGAT enzyme activities, and the expression of related genes, along with an increase in the pH of the hydroponic nutrient solution. These findings suggest that VcAMT14 plays a crucial role in regulating N response in blueberry under ERMF symbiosis, providing important insights into the mycorrhiza-mediated N uptake mechanism.