Elucidation of proline metabolic enzymes in the cytoplasmic male sterility in Capsicum annuum L.

Pepper cytoplasmic male sterility (CMS) line 9704A is one of the CMS types used for hybrid pepper (Capsicum annuum L.) production in China. Our previous studies suggested that proline content in the anthers of pepper CMS-9704A was lower than that of the maintainer line 9704B at the abortion stage. To elucidate the metabolic mechanism of proline in the CMS-pepper anthers, the changes of gene expression related to proline metabolic enzymes were investigated in the anther of CMS-9704A and maintainer-9704B. At the abortion stage (pollen mother cell meiosis stage to mature pollen stage), there were lower activities of glutamate dehydrogenase (GDH), Delta 1-pyroline-5-carboxylate synthetase (P5CS), Delta 1-pyrroline-5-carboxylate reductase (P5CR), ornithine-delta-aminotransferase (delta OAT) and Arginase in the anthers of CMS-9704A than those of the maintainer-9704B (except P5CR in the stage 2 and Arginase in stage 3). Simultaneously, activities of proline dehydrogenase (ProDH) in the anthers of CMS-9704A did up-regulate than those in the maintainer-9704B. Abundance of GDH, P5CS, P5CR, delta OAT, Arginase and ProDH mRNA in anthers of CMS-9704A corresponded with the activities of these genes. Therefore, it indicates it is the abnormalities of proline biosynthesis and degradation that result in the deficiency of proline in the CMS in the microspore development.