Fig. 8.

A proposed model of programmed cell death in plant and animal cells. a In plants, the deficiency of MOD1 leads to an increased level of NADH in the chloroplast, which drives OAA to be converted to malate by plNAD-MDH. Malate carrying the reducing equivalents is transported out of the chloroplast into the cytosol by DiT1, and then be transported into the mitochondrion by an unidentified transporter or transporters. In the mitochondrion, malate is converted to OAA by mMDH1, and simultaneously NADH is generated to provide electrons for mETC to induce the ROS formation and initiate the PCD process in the mod1 cells. b In HeLa cells, exogenous malate could be taken into the cytosol, and then transported into the mitochondrion by the malate/α-ketoglutarate (α-KG) transporter. In the mitochondrion, malate is converted to OAA by MDH2, and simultaneously NADH is generated to provide electrons for mETC to induce the ROS formation and initiate the cell death process, which is highly conserved with the PCD in mod1 plants