Monitoring programmed cell death triggered by mild heat shock in soybean-cultured cells

Programmed cell death (PCD) is a common form of cellular demise during plant response to environmental stresses. The pathway of PCD has been partially clarified in plants although the underlying molecular mechanisms are still poorly defined. We have investigated the signalling cascade induced by a mild heat treatment causing PCD in soybean cells (Glycine max L.). The data show that heat shock led to the onset of PCD in soybean cells involving H₂O₂ production and mitochondrial damage. Cytochrome c release accompanies the presence of caspase 9-like and caspase 3-like protease activities. Concomitantly, cells were severely damaged with a progressive cell shrinkage, chloroplast alteration and detachment of the plasma membrane from the cell wall. Chromatin condensation and DNA damage were observed. It is proposed that a mild heat stress induces PCD in soybean cells through a caspase-like-dependent pathway.