Plant & Animal Genomes XIII Conference

January 15-19, 2005
Town & Country Convention Center
San Diego, CA

Cytoplasmic Regulation Of The Accumulation Of Nuclear-Encoded Proteins In The Mitochondrial Proteome Of Maize

Patrick S. Schnable¹ , Frank Hochholdinger²

¹  Iowa State University, 2035B Roy J. Carver Co-Laboratory, Ames, IA, 50011-3650, USA

²  Zentrum Fur Molekularbiologie Der Pflanzen (ZMBP) - Allgemeine Genetik, Auf Der Morgenstelle 28, Tubingen, D-72076, Germany

Mitochondria from normal (NA-) and T-cytoplasm maize (Zea mays L.) were purified from unpollinated ears via Percoll centrifugation. Approximately 300 mitochondrial proteins were resolved using two-dimensional electrophoresis. The 197 most abundant proteins were analyzed by MALDI-ToF mass spectrometry involving overlapping pH gradients (pH 4-7 and 6-9). Database searches identified 58 genes that encode 100 of these protein spots. Functions could be predicted for 38 of the 58 genes (66%). All but one of these genes are located in the nuclear genome. 13% of analyzed protein spots (25/197) exhibited at least a three-fold difference in accumulation between the mitochondrial proteomes of NA- or T-cytoplasm maize plants that had essentially identical nuclear genomes. Because most of these proteins were nuclear-encoded, these findings demonstrate that the genotype of a mitochondrion can regulate the accumulation of the nuclear-encoded fraction of its proteome. About half (27/58) of the maize mitochondrial proteins identified in this study were not recovered in previous analyses of the Arabidopsis and rice mitochondrial proteomes.