OsAMT1.3 expression alters rice ammonium uptake kinetics and root morphology

High-affinity ammonium transporters (AMT1) are responsible for ammonium (NH4 (+)) acquisition and/or perception in the micromolar range, and their expressions can be differentially regulated by nitrogen (N) availability. The present study characterised the functions of the rice (Oryza sativa) OsAMT1.3 transporter to understand its contribution to NH4 (+) acquisition and plant adaptation to environments with low N availability. Transgenic rice plants were obtained to study the activity of the OsAMT1.3 promoter (P (OsAMT1.3) :GFP:GUS) and the overexpression of the OsAMT1.3 gene (UBIL:OsAMT1.3:3xHA) in plants. The OsAMT1.3 promoter activity was induced strongly in the absence of N and occurred primarily in the zones of lateral root emission and root tips. Anatomical sections of the segment of root tips and the middle third showed a differential pattern of OsAMT1.3 activity. Analysis of the OsAMT1.1-1.3 transporter expression profiles indicated that overexpression of OsAMT1.3 positively affected OsAMT1.2 expression. When subjected to a low N supply, plants overexpressing OsAMT1.3 showed lower K (M) and C (min) values. Additionally, these lines showed longer roots with a higher area, volume, and number of tips. The data suggested that OsAMT1.3 is involved in the ability of rice plants to adapt to low NH4 (+) supplies.