Arabidopsis LSD1 gene plays an important role in the regulation of low temperature-dependent cell death

In higher plants, the crosstalk between cold stress responses and reactive oxygen species (ROS) signaling is not well understood. Two chilling- sensitive mutants, chs4-1 and chs4-3, were characterized genetically and molecularly. The CHS4 gene, identified by map-based cloning, was found to be identical to LESION SIMULATING DISEASE RESISTANCE 1 (LSD1). We therefore renamed these two alleles lsd1-3 and lsd1-4, respectively. These two mutants exhibited an extensive cell death phenotype under cold stress conditions. Consistently, lsd1-3 plants exposed to cold showed up-regulation of the PR1 and PR2 genes, and increased accumulation of salicylic acid. These results indicate that low temperature is another trigger of cell death in lsd1 mutants. Furthermore, lsd1-3 plants accumulated higher concentrations of H₂O₂ and total glutathione under cold conditions than wild-type plants. Genetic analysis revealed that PAD4 and EDS1, two key signaling regulators mediating resistance responses, are required for the chilling-sensitive phenotype of lsd1-3. These findings reveal a role of LSD1 in regulating cell death trigged by cold stress and a link between cold stress responses and ROS-associated signaling.