Monitoring the Expression Pattern of Genes Coding Betaine Aldehyde Dehydrogenase (BADH) Enzymes in Arabidopsis under Drought Stress

Compatible solutes or osmoprotectants serve as nontoxic solutes for cytoplasmic osmoregulation. Glycine betaine is one of the most critical compatible solutes accumulated by many plants in response to adverse effects of various abiotic stresses. In some species named Glycine betaine accumulators, Glycine betaine is synthesized by a two-step oxidation of choline by choline monooxygenase (CMO) and betaine aldehyde dehydrogenase (BADH) enzymes. According to the Arabidopsis thaliana genome database (TAIR) there are the most likely two AtALDH8 and AtALDH9 genes coding BADH enzyme. In this study, using the relative expression analysis via quantitative RealTime PCR, it has been evaluated how the expression pattern of these genes affected by drought levels in Arabidopsis thaliana tissues including fast expanding leaves, fully expanded leaves, and roots. It has been denoted that the mRNA induction level of the AtALDH9 gene varies in tissues in response to drought levels. However, the expression of AtALDH8 gene is affected negligibly by these factors. While 12-day of water withholding made no changes in the expression level of AtALDH9 gene in fully expanded leaves, the expression level of the gene were changed at about 0.7-fold and 4-fold in fast expanding leaves and roots, respectively. Differently, after 16-day of water withholding the expression level of AtALDH9 gene rose about 2.5-fold in fast expanding leaves and reduced about 0.2-fold in both fully expanded leaves and roots. Generally, it seems that AtALDH9 is the gene accountable in Arabidopsis in response to drought stress.