Proteome analysis of the normal and Ogura (ogu) CMS anthers of Brassica napus to identify proteins associated with male sterility

In the Ogura (ogu) cytoplasmic male sterility (CMS) system in Brassica napus L., male sterility is caused by a defect in the mitochondrial gene and, under our growth conditions, stamens produced are carpelloid. We analyzed the proteome of ogu and normal anthers with the objective of identifying differentially expressed proteins and their potential roles in pollen development and male sterility. By using differential in-gel electrophoresis, we detected over 2300 spots on 2-D gels of normal and ogu anthers and of the 167 spots with 2-fold or higher expression, 120 were analyzed by MALDI-TOF/TOF mass spectrometry and 94 proteins were identified searching against NCBI and Brassica EST databases. Proteins up-regulated in normal anthers included those associated with carbohydrate and energy metabolism (e.g., fructose bisphosphatase, ATP synthase, malate dehydrogenase, and cytochrome c oxidase), cell wall remodeling (e.g., β-1,3-glucanase and pectinesterase), aldehyde dehydrogenase (ALDH), photosynthesis, and flavonoid synthesis. Proteases were identified in both the normal and ogu anthers, but a number of protease inhibitors were up-regulated in ogu anthers. The activities of ALDH and β-1,3-glucanase were also much higher in normal anthers by comparison with ogu anthers. This study documents the proteomic basis of mitochondrial–nuclear interaction in the control of ogu CMS in B. napus.