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 NH4+ transport ( HATS) activity. We measured (NH4+)-N-13 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. (NH4+)-N-13 influx was higher for the overexpression lines of Jarrah line when grown at 10 mu M external NH4+ concentration, but not for the overexpression lines of Taipei. For seedlings grown at 2 mM external NH4+ 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 NH4+ concentrations were either reduced or showed no statistically significant differences compared with wild type lines. While (NH4+)-N-13 influx into roots of Jarrah line 75-4 grown at 10 mu M external NH4+ concentration was significantly higher than in wild type, measurements of (NH)-N-13 efflux revealed no differences, and thus net uptake of NH4+ was higher in this overexpression line.