Abstract
Polyunsaturated fatty acids, which are major components of biomembrane, are known to be easily peroxidized in response to oxidative stress. When lipid hydroperoxides break down, a great diversity of aldehydes is formed. In model experiments in vitro, we found that a highly reactive aldehyde, malondialdehyde (MDA) was generated from linolenic acid methylester in the presence of reactive oxygen species, and MDA attached to proteins in a temperature-dependent manner. Therefore, we focused into physiological roles of MDA in heat-stressed plant. Treatment of 1 μM MDA to Arabidopsis plants enhanced heat tolerance without induction of heat shock protein (HSP) genes, suggesting that MDA concerns in HSP-independent heat tolerance. On the other hand, several chloroplast proteins in Arabidopsis heat-treated at 40oC were drastically modified by MDA. In this presentation, we present discuss and two physiological roles of MDA generated from peroxidized linolenic acid as "signal molecule" and "protein-modifying agent" in heat-stressed plants.
