Abstract
Recent studies showing that overexpression of aldehyde-detoxifying enzymes improved stress tolerance of the transgenic plants demonstrate the cytotoxicity of the lipid peroxide-derived aldehydes in plants. In order to identify the chemical species of the aldehydes responsible for cellular injury in plants under environmental stresses, we analyzed aldehyde profiles in oxidatively stressed leaves, using HPLC after derivatizing the acetonitrile extracts of leaves with 2,4-dinitrophenylhydrazine. Non-stressed tobacco leaves contained at least 12 aldehyde species, ca. 20 nmol aldehydes/g fresh weight in total. n-Hexanal and 3Z-hexenal were the major components. Very short-chain aldehydes like propionaldehyde and butyraldehyde were also detected. In the ozone-treated leaves, the contents of these aldehydes were 10-fold higher, and additional aldehydes such as acetaldehyde and 2E-hexenal, which is a potent cytotoxin, were observed. The content of malondialdehyde was less than 1% of the total aldehydes in both stressed and non-stressed leaves.
