Ornithine aminotransferase (OAT) enzyme catalyzes the transfer of the delta-amino group from Lornithine to oxo-glutarate. In plants, this reaction biochemically connects urea cycle, proline cycle, and poliamines biosynthesis pathway. OAT activity is usually associated with biotic and abiotic stress response and nitrogen metabolism. Our previous results show that OAT promoter activity is associated with growth zones. The aim of present study is to investigate the transcriptional regulation of the plant OAT gene in Arabidopsis thaliana. The transcriptional regulation of OAT gene was investigated on A. thaliana plants with reporter gene system containing E.coli β-glucuronidase gene (GUS) under A. thaliana OAT gene promoter control. Seedlings were treated with different growth regulators; the promoter activity was analyzed histochemically. The reporter protein expression was observed in response to different forms of auxin (IAA, NAA, and 2,4D), cytokine (6-BAP), and ethylene precursor (ACC). These results allow us to suggest the role of OAT gene in plant cell proliferation and expansion. The results show that OAT gene might be involved in plant growing processes.