Abstract：Programmed cell death (PCD) is essential for normal development and reproduction which is also induced by various biotic or abiotic stress. Aluminum (Al) stress is a major factor limiting plant growth and yield of crops in acid soils. One of Al toxicity on cells is induced PCD. Whether Al stress causes soybean cell apoptosis is still poorly understood. In this study, 4',6-diamidino-2-phenylindole (DAPI) staining and content assays of mitochondrial cytochrome c (Cyt c) were performed in Tamba black soybean (Glycine max) root tip cells under Al stresses. DAPI staining results showed that there was a nucleus aggregation in the cell edge, and nuclear chromatin condensation displayed a crescent-shaped distribution around the nucleus with dense stain. The content of mitochondrial malondialdehyde (MDA) of soybean root tip cells increased with the increased Al concentration and time of Al treatment, which suggested that the degree of mitochondrial membrane oxidation increased and membrane damage became more serious. Cyt c/a can reflect the content change of Cyt c within the inner mitochondrial membrane. Mitochondrial permeability transition pore (MPTP) of soybean root tip cells opened unceasingly, mitochondrial membrane potential (ΔΨm) decreased, mitochondrial membrane integrity was destroyed under Al stress promoting Cyt c off from the inner mitochondrial membrane. A reduced value of mitochondrial Cyt c/a and content of Cyt c under Al stress suggested that Cyt c might be released from mitochondria to the cytoplasm through the mitochondrial membrane. These findings, from cellular and physiological level, revealed the roles of mitochondria and Cyt c in Al-induced PCD of Tamba black soybean root tip cells, will furtherly know about PCD process induced by Al tress and toxic mechanisms of Al to plants.
