Differential Expression of Mitochondrial Proteins Between C-Type Cytoplasmic Male Sterility Line C48-2 and Its Maintainer Line in Maize

To seek some evidence and explanation for the sterility mechanism of C-type cytoplasmic male sterility (C-CMS) in maize (Zea mays L.), a C-type sterile line (C48-2) and its maintainer (N48-2) were used, for analyzing the differential expression of their anther mitochondrial proteome. The mitochondrial proteins in the anthers were separated first by two-dimensional electrophoresis, with immobilized pI (3–10, nonlinear) gradients, and later by SDS-PAGE. The Coomassie brilliant blue-stained protein spots were analyzed using software PDQUEST. There were about 260 detectable spots on each 2D-gel. With direct MALDI-TOF mass spectrometry analysis and protein database searching, only 2 out of 10 protein spots were selected as important candidates, based on reliability and differential amounts. They were putative glutamate dehydrogenase (GDH) and voltage-dependent anion channel protein-1 (VDAC1), respectively. Both of them were upregulated in the mononuclear phase of C48-2. The GDH exists mainly in mitochondria of higher plants and plays an important role in nitrogen metabolism. The upregulation of GDH affects the normal energy supply during plant development, probably leading to cytoplasmic sterility. The VDAC1 plays an essential role not only in the permeability of the mitochondrial membrane, but also in apoptosis, mediated by the mitochondrial pathway. Overexpression of VDAC1 in a variety of cells induces apoptotic cell death, indicating that VDAC1 functions as a conserved mitochondrial element of the death machinery. It is suggested that GDH and VDAC1 in the mitochondria probably cause the sterility in C-CMS in maize.