The present invention relates to transgenic plants that have increased nitrogen use efficiency, stress tolerance, and/or alleviating a limitation such that yield is increased, or a combination of these and that have been transformed using a novel vector construct including a synthetic N-acetyl glutamate kinase (NAGK) gene that modulates nitrogen use in plants. The invention also includes the overexpression and enzymatic characterization of an arginine-insensitive NAGK isolated from a bacterial strain that improves stress tolerance and nitrogen uptake, metabolism or both. In various embodiments, the vector construct includes one or more nucleic acid sequences including SEQ ID NO: 1. The invention also relates to isolated vectors for transforming plants and to antibodies used for detecting transformed plants. The invention also relates to methods of expressing in plants the nucleic acid molecules corresponding to the nucleic acid sequences that modulate nitrogen use in plants or are modulated by nitrogen conditions.