Isolating the promoter of a stress-induced gene encoding betaine aldehyde dehydrogenase from the halophyte Atriplex centralasiatica Iljin.

The betaine aldehyde dehydrogenase (AcBADH) gene of the halophyte Atriplex centralasiatica Iljin is induced by drought, salinity, cold stress and abscisic acid, in parallel with an increase in betaine level. In order to study the molecular basis of its expression and to obtain an effective stress-induced promoter, the 5' flanking region of betaine aldehyde dehydrogenase gene (about 1.2 kb) was isolated from the halophyte A. centralasiatica Iljin by screening the genomic library. The transcription start site, which localized at 84 bases upstream of the start ATG, was determined by primer extension and 5'-RACE method. To investigate the molecular mechanism of the stress-induced gene regulation, the AcBADH promoter-beta-glucuronidase chimeric gene constructs containing six deletions were introduced into tobacco by Agrobacterium-mediated transformation. The AcBADH 5'-flanking region, a promoter strongly induced by salt stress, contains two salt-responsive enhancer regions localized between -1115 and -890, -462 and -230 and one silencer region between -890 and -641.