ROOT SPECIFIC EXPRESSION OF ahybadh4 GENE PROMOTER IN TRANSGENIC Arabidopsis thaliana PLANTS

Abstract

Glycine betaine is one of the most efficient solutes compatible with metabolism. In plants glycine betaine is synthesized in two enzymatic steps. First, choline is oxidized to betaine aldehyde by a choline monooxygenase (CMO); the second step is catalyzed by a betaine aldehyde dehydrogenase (BADH) that converts betaine aldehyde to glycine betaine. Previous studies had shown that the ahybadh17 gene transcription is induced by water stress and salinity, in parallel to an increase of glycine betaine levels. In the present study the expression of the ahybadh4 gene from Amaranthus hypochondriacus in Arabidopsis thaliana transgenic plants was analysed. For this purpose a chimeric gene was constructed with a 1.5 kb sequence corresponding to the putative promoter of the ahybadh4 gene fused to the GUS reporter gene (uid A). Seeds obtained from these transgenic plants (T₃) were grown during 7, 14 and 21 days after germination and subjected to osmotic stress and abscisic acid (ABA) treatments for a period of 16 hours. The histochemical and fluorimetric analyses of GUS showed a constitutive and root-specific expression. These results allowed to conclude that the 1.5 kb 5’-sequence of the ahybadh4 gene is not regulated by osmotic stress or ABA in A. thaliana.