Characterization of a novel flooding stress-responsive alcohol dehydrogenase expressed in soybean roots.

Alcohol dehydrogenase (Adh) is the key enzyme in alcohol fermentation. We analyzed Adh expression in order to clarify the role of Adh of soybeans (Glycine max) to flooding stress. Proteome analysis confirmed that expression of Adh is significantly upregulated in 4-day-old soybean seedlings subjected to 2 days of flooding. Southern hybridization analysis and soybean genome database search revealed that soybean has at least 6 Adh genes. The GmAdh2 gene that responded to flooding was isolated from soybean cultivar Enrei. Adh2 expression was markedly increased 6 h after flooding and decreased 24 h after floodwater drainage. In situ hybridization and Western blot indicated that flooding strongly induces Adh2 expression in RNA and protein levels in the root apical meristem. Osmotic, cold, or drought stress did not induce expression of Adh2. These results indicate that Adh2 is a flooding-response specific soybean gene expressed in root tissue.