OsDof25 expression alters carbon and nitrogen metabolism in Arabidopsis under high N-supply

To verify the effect of the transcription factor OsDof25 on the nitrogen metabolism in plants, it was cloned for expression in Arabidopsis thaliana under the control of the 35S promoter. Lineages with different expression levels of this gene were obtained, and when grown in a half-strength MS medium (10 mM of NH4 (+) and 20 mM of NO3 (-)) showed phenotypes with visible chloroses and growth disorders. It was observed that OsDof25 increased the levels of expression of high and low affinity ammonium transporters (AtAMT1.1 and AtAMT2.1, respectively) and repressed the high affinity nitrate transporter (AtNRT2.1). We also verified an increase in total amino-N content and expressions of the pyruvate kinase (PK1 and PK2), phosphoenolpyruvate carboxylase (PEPC1 and PEPC2) and NADP-dependent and NAD-dependent isocitrate dehydrogenase. In addition, an increase in expression levels and activity of glutamate dehydrogenase was also observed. The simultaneous increase in the expression of AMTs and enzymes of carbon metabolism may explain the high levels of amino-N found in the transgenic plants. The data found in this work suggest that OsDof25 expression simultaneously affects NH4 (+) uptake and organic acid metabolism in plants.