Mung bean (Vigna radiata), an important legume crop, has the property of desiccation tolerance (DT), which is lost in the final stage of germination (preimbibition, 18 h-24 h). We compared parameters related to the programmed cell death (PCD) of mung bean seeds before and after
dehydration at different imbibition stages through various detection methods. The results of
Evans blue and TTC staining methods showed that the
dehydration process could lead to cell death. The results of optical and subcellular morphology showed that PCD occurred after
dehydration. The destruction of
DNA integrity and the activity changes in
caspase and total nuclease in mung bean seeds after
dehydration treatment indicated that the loss of desiccation tolerance was related to PCD.
Dehydration resulted in the destruction of the mitochondrial structure, reversal of the membrane potential, and the entrance of
cytochrome C into the cytoplasm. These processes all indicate that the mitochondrial apoptosis pathway was the main form of
dehydration-induced PCD. The results of cytoplasmic Ca2+ concentration showed that Ca2+ signaling also played a role in inducing PCD, with the upstream signal being
dehydration-induced changes in water potential and the downstream signal being the ROS and mitochondrial PT channel, according to the order in which these signals happened. The mitochondrial apoptosis pathway can be considered the main mechanism of
dehydration-induced PCD based on our analysis of the sequence of major events in PCD. The main processes include
dehydration induction, changes in Ca2+ and mitochondrial respiratory electron transport, the reversal of mitochondrial membrane potential induced by ROS and Ca2+, and the transmission and execution of PCD downstream signals induced by
cytochrome C release.