Genome-wide Identification of Torreya grandis AMT Family Genes Revealed the Function and Regulation of the Nitrogen Stress Responsive Gene TgAMT5

Background Ammonium transporters (AMTs) are a class of transmembrane proteins widely found in plants, bacteria, fungi, and other organisms, mediating transmembrane ammonium nitrogen (NH ₄ ⁺ ) transport, which is one of the crucial pathways for plants to obtain nitrogen from resources. AMTs have been studied in many plants but have not been systematically analyzed in Torreya grandis . Results This study first used bioinformatics to identify members of the T . grandis AMT family and then real time quantitative PCR to explore their tissue expression patterns and abiotic stress responses. The physical and chemical properties, secondary structure, and evolutionary relationships of the encoded proteins were ascertained. There were ten members of the gene family, named TgAMT1 – TgAMT10 , which were located on six chromosomes, with coding sequence lengths of 975–1629 bp. Subcellular localization predicted all members to be located on the plasma membrane. Phylogenetic analysis divided the TgAMTs into two subfamilies, AMT1 and AMT2. There were significant differences in gene structure and conserved motifs among the subfamilies, but Motif 1, Motif 3, and Motif 4 were common to all. The expression of TgAMTs was histologically specific. Additionally, nitrogen morphology also affected TgAMTs expression. TgAMT5 was identified as a potential member involved in the response to NH ₄ ⁺ -induced stress. The gene function of TgAMT5 was verified in transgenic A . thaliana and was found to promote plant growth and development, especially root growth, by absorbing ammonium salt through roots. In addition, dual-luciferase and yeast one-hybrid assays showed that the transcription factor TgWRKY2 could directly bind to the TgAMT5 promoter and enhance its expression. Conclusion This study can provide theoretical basis for the efficient use of nitrogen in Torreya grandis , and lay a foundation for exploring nitrogen uptake and utilization in gymnosperms.