Functional characterisation of OsAMT1.1 overexpression lines of rice, Oryza sativa.

In rice (Oryza sativa L.) OsAMT1.1 is the most active and / or most N-responsive gene responsible for high-affinity NH transport (HATS) activity. We measured NH influx and plant biomass in transgenic overexpression lines and two wild type cultivars of rice, Jarrah and Taipei, with one or more copies of OsAMT1.1. NH influx was higher for the overexpression lines of Jarrah line when grown at 10 µm external NH concentration, but not for the overexpression lines of Taipei. For seedlings grown at 2 mm external NH concentration Jarrah lines 77-1 and 75-4 showed an increased influx; however, two overexpression lines of Taipei showed reduced influx rates. The biomasses of the transgenic lines grown at low and high external NH concentrations were either reduced or showed no statistically significant differences compared with wild type lines. While NH influx into roots of Jarrah line 75-4 grown at 10 µm external NH concentration was significantly higher than in wild type, measurements of NH efflux revealed no differences, and thus net uptake of NH was higher in this overexpression line.