Cytological and iTRAQ-based quantitative proteomic analyses of hau CMS in Brassica napus L

Hau cytoplasmic male sterility (CMS) is a new type of CMS that was originally identified in Brassica juncea and subsequently transferred to B. napus and B. rapa. To further elucidate the molecular mechanism underlying hau CMS in B. napus, semithin section analysis and iTRAQ-based differential proteomic analysis were performed to compare the hau CMS and its maintainer line. Cytological analysis revealed that abnormal anther development in the hau CMS line was arrested during the differentiation of stamen archesporial cells. qRT-PCR analysis showed that the sterility gene orf288 was expressed at substantially higher levels in CMS anthers than in anthers with restored fertility. In comparison with the maintainer line, a total of 186 differentially abundant proteins were identified in the CMS line, 58 of which exhibited increased accumulation and 128 exhibited decreased accumulation. Bioinformatics analysis showed that proteins involved in carbohydrate and energy metabolism, such as those involved in oxidative phosphorylation, glycolysis/gluconeogenesis and pyruvate metabolism, exhibited decreased accumulation in the hau CMS line, whereas those involved in oxidative stress, antagonism of cell death and protein processing exhibited increased accumulation in the hau CMS line, indicating the potential roles of carbohydrate metabolism and energy supply in the regulation of hau anther abortion. BIOLOGICAL SIGNIFICANCE: Cytoplasmic male sterility (CMS) is one of the most efficient ways to produce hybrid seeds in crops. CMS is mainly caused by mitochondrial mutation and has been an important model for investigation of cytoplasmic and nuclear interactions in various plant species. Hau is a new type of CMS line in Brassica with completely abortive anthers. Although studies have been conducted to identify the key genes associated with CMS, the molecular mechanisms underlying hau CMS remain unclear. In this study, cytological, molecular, and proteomic approaches were used to reveal the mechanism underlying hau CMS in B. napus. Based on a comparison of the protein expression profiles of the hau CMS line and its maintainer line to elucidate the mechanisms underlying hau CMS, a potential protein regulatory network is proposed herein. These results may provide new insights into the molecular basis of hau CMS in B. napus.