Abstract
Acetaldehyde is oxidized from anaerobically accumulated ethanol during re-aeration in plants and may cause post-anoxic (post-hypoxic) injury. Aldehyde dehydrogenase (ALDH) can metabolize acetaldehyde to acetate, which is much less toxic. To understand the role of ALDH in alleviating post-anoxic injury of plants, we analyzed the expression of the mitochondrial ALDH genes, rf2a and rf2b, and determined the ethanol and acetaldehyde contents under submergence and subsequent re-aeration in a submergence-intolerant plant, maize (Zea mays L., inbred line B73). The level of rf2a mRNA decreased, whereas that of rf2b mRNA increased under submerged conditions. When the submerged plants were re-aerated, the transcript levels returned to the original levels. The level of mitochondrial ALDH proteins decreased under submergence and remained unchanged under re-aeration. The ALDH activity decreased under submergence and, during re-aeration, recovered to the original level much more slowly than in the case of rice (Oryza sativa L.). The content of acetaldehyde, which was produced under submergence, further increased following re-aeration. These results suggest that the lower submergence tolerance of maize compared to that of rice is partly due to a weaker ALDH activity during re-aeration.
