Proceedings of the XLVII Italian Society of Agricultural Genetics - SIGA Annual Congress

Verona, Italy - 24/27 September, 2003

ISBN 88-900622-4-X

Poster Abstract - 1.10

CHARACTERISATION OF THREE FUNCTIONAL HIGH AFFINITY AMMONIUM TRANSPORTERS IN LOTUS JAPONICUS WITH DIFFERENTIAL TRANSCRIPTIONAL REGULATION AND SPATIAL EXPRESSION

A. ROGATO, E. D’APUZZO, U. SIMON-ROSIN, H. EL ALAOUI, A. COSTA, A. BARBULOVA, A.-M. MARINI, K. M. UDVARDI, F. LO SCHIAVO, M. CHIURAZZI

Institute of Genetics and Biophysics “A. Buzzati Traverso”, Via Marconi 12 80125, Napoli, Italy

N metabolism, symbiosis, nodule organogenesis

Ammonium is a primary source of nitrogen for plants. In legume plants ammonium can be additionally obtained by the nodule infected cells as result of the symbiotic nitrogen fixation. NH₄⁺ is not only the final product of symbiosis but also a main regulator of the early as well as late symbiotic interaction steps and hence ammonium transporters are likely to play important roles in the control of nodule formation and functioning. PCR techniques were used to isolate two new full-length clones of L. japonicus homologue of LjAMT1;1 (LjAMT1;2 and LjAMT1;3) and the 5’ regulatory sequences of the three members. The full-length cDNAs when cloned into the yeast expression vector pMET426 were able to complement a yeast mutant unable to grow on media with NH₄⁺ as the sole nitrogen source. A measurement of the accumulation of [¹⁴C]methylamine in the yeast strains expressing the three LjAMT1 genes permitted their biochemical characterization and differentiation. The observed biochemical features were correlated with the transcripts abundance observed in mature plants grown in hydroponics conditions in presence of different N regimes. The expression patterns of the three LjAMT1 members were examined in different organs and a 60% decreased expression of LjAMT1;1 was observed in leaves of plants growing under high CO₂ conditions. Furthermore, we report a map of the pattern of expression of the Lotus AMT1 members obtained by promoter-gusA fusions analysis, mRNA in situ and GFP-fusion localizations.