A betaine aldehyde dehydrogenase gene from Ammopiptanthus nanus enhances tolerance of Arabidopsis to high salt and drought stresses

Glycine betaine functions as an osmotic protectant in response of plant to abiotic stresses. In higher plants, the betaine aldehyde dehydrogenase (BADH) catalyzes the key step of glycine betaine biosynthesis. A lot of effort has been paid to cloning and heterologous expression of the BADH genes from different plants. However, different phenotypes were observed from the transgenic plants. Diversity of subcellular location and functions was found among the members of the BADH family. Our previous report described the cloning of an AnBADH gene from xerophyte Ammopiptanthus nanus and preliminary functional validation in Escherichia coli. In the present study, the function of the AnBADH gene for abiotic tolerance was further characterized by quantitative real time PCR and heterologous expression in Arabidopsis mutant. The results showed that the endogenous expression of the AnBADH gene was strongly induced by the treatments of high salt, dehydration, abscisic acid, heat, and cold. The heterologous expression of the AnBADH gene significantly enhanced tolerance of the Arabidopsis mutant to high salt and drought stresses. Under the stress conditions, the transgenic lines exhibited a more robust root system and a larger fresh weight, higher content of glycine betaine and proline, higher relative water content, lower relative electrolyte leakage and malondialdehyde content, compared to the untransformed mutant. These results suggest that the AnBADH gene encodes a functional betaine aldehyde dehydrogenase, and plays a critical role in the adaptation of A. nanus to its harsh habitat. It provides one more choice for genetic improvement of commercial crops for abiotic tolerance.