Chitosan induces Ca2+-mediated programmed cell death in soybean cells

• Chitosan, a component of the cell wall of many fungi, has been widely used to mimic pathogen attack and has been shown to induce several defence responses. • Here we show that low concentrations (50 μg ml−1) of chitosan are able to induce an increase in cytosolic Ca2+ concentration ([Ca2+]cyt), accumulation of H2O2 in the culture medium, induction of the defence gene chalcone synthase (chs), and cell death in soybean cells (Glycine max). • Chitosan-induced cell death occurred through cytoplasmic shrinkage, chromatin condensation and activation of caspase 3-like protease, suggesting the activation of a programmed cell death (PCD) pathway. Buffering extracellular Ca2+ with the Ca2+ chelator EGTA prevents [Ca2+]cyt elevation, H2O2 production and all downstream PCD features, but not cell death. • Higher doses (200 μg ml−1) of chitosan evoked neither Ca2+ transient and H2O2 production nor caspase 3-like activation, but caused cell death, possibly as a result of plasma membrane disturbance.