Molecular and cellular characterizations of a cDNA clone encoding a novel isozyme of aldehyde dehydrogenase from rice

Aldehyde dehydrogenases (ALDHs) are a group of enzymes catalyzing the conve rsion of aldehydes to the corresponding acids. In mammals and yeasts, at le ast two isozymes of ALDH are known to be involved in ethanol metabolism (cy tosolic ALDH1 and mitochondrial ALDH2). Although mitochondrial ALDH isozyme s have previously been identified in several plants, such as maize and toba cco, it is unclear whether cytosolic ALDH isozymes also exist in plants. In this study, we identified and characterized a cDNA clone encoding aldehyde dehydrogenase (ALDH1a) from rice (Oryza sativa L. cv. Nipponbare). The ope n reading frame of this clone did not contain a typical mitochondrial targe ting signal. Analysis of the subcellular localization of ALDH1a using green fluorescent protein (GFP) suggested that ALDH1a is a cytosolic enzyme rath er than a mitochondrial enzyme. A genomic Southern hybridization indicated that sequences homologous to the ALDH1a gene are present in at least two re gions of the rice genome. Amplification by RT-PCR showed that ALDH1a is exp ressed strongly in roots, but not in leaves, of rice seedlings, suggesting that ALDH1a functions in roots. (C) 2000 Elsevier Science B.V. All rights r eserved.