Poster: Membrane Transport

Abs # 1230: Molecular physiology of ammonium transporters in a. thaliana

Presenter:	Schäfer, Arne , schaefer@mpimp-golm.mpg.de
Authors	Schäfer, Arne  (A)
Affiliations:	(A): Max Planck Institute for Molecular Plant Physiology

Nitrogen availability often represents a limiting factor for plant growth. An important step in the improvement of crop plants is the understanding of the primary acquisition process of nitrogen in plants. NH4+ is an essential source of nitrogen for plants and is taken up into cells by a transport system with high specifity for NH4+. In A. thaliana this system consists of six homologous genes each encoding for an individual NH4+-transporter of which specific function little is known at present.In a reverse genetics approach T-DNA insertion lines have been developed for individual AMT family members and analysed. To further elucidate the roles of the transporters, double mutants of these lines were crossed. Furthermore a RNA interference approach has been used to disrupt expression of multiple AMT family members. To date, the most severe phenotype has derived from studies using the RNAi-lines. Single and double insertion lines have not shown any significant differences at the whole plant level. All lines were subjected to 14C-methylammonia and 15N-ammonia uptake assays, real-time PCR, metabolic profiling (HPLC/CE) and various developmental and morphological studies. Ongoing results will be presented including discussions of possible compensation within a gene family and the efficacy of RNAi in effecting multi-gene interference. Uptake kinetics suggest the existence of a distinct low specific NH4+-uptake mechanism. Various publications suggest that K+-transporters could play a significant role in transporting NH4+-across plant membranes.To investigate their involvment in NH4+-transport,double mutants of the K+-channel AKT1 and the NH4+-transporters AMT1.1 and AMT1.2 are prepared. Additionally, the RNAi-AMT1.1 construct was transformed into the AKT genetic background.