Comparative Proteomics Research Of Heterosis Of Sorghum-sudangrass Hybrids

Sorghum-sudangrass hybrids are typically used for studying heterosis in forage crops, however, the molecular details underlining heterosis in this crop still remain largely unknown. Proteomics research provides a new method to analyze the molecular mechanism of heterosis. In this study, sorghum-sudangrass hybrids and their parents as experimental materials, we carried out quantitative proteomic analysis on three genotypes of leaves and roots at the three-leaf stage and mature embryo which were analyzed combining 2-DE method based on gel and label free method based on non-gel with mass spectrometry, respectively. We identified differential protein to elucidate molecular mechanism of heterosis of sorghum-sudangrass hybrids and accumulate data of genetic basis of heterosis. The results are as follows:1. We builted a high resolution and good repeatability two dimensional electrophoresis maps of sorghum-sudangrass hybrids which using acetone precipitation method to extract total leaf protein,17 cm pH 4-7 IPG strip, and loading quantities with 800ug.2. The comparative analysis of 2-DE and label free method indicated that label free method was more suitable for proteomics research.3. Protein identification results of 2-DE and label free method showed that additive and non-additive proteins were essential to the vigor of leaves of sorghum-sudangrass hybrids, the proportion of non-additive proteins was significantly higher than the additive proteins, which indicated that non-additive proteins played a prominent role in heterosis. Of the non-additive proteins, pattern of high-parent expression was the largest proportion.4. The functional and bioinformatics analysis of proteins showed that photosynthesis in leaves of sorghum-sudangrass hybrids was heightened to assimilate more organic matter, so that hybrids could effectively maintain the plant growth and development, this was the main reason of heterosis.5. We performed differential proteomics study of roots and mature embryo of sorghum-sudangrass hybrids and its parents which using label free method combined with mass spectrometry, qualitative analysis results showed that 3077 and 4366 nonredundant proteins identified in roots and mature embryo of three genotypes, respectively.6. Proteins in the roots of sorghum-sudangrass hybrids and their parents were identified and analyzed using quantitative proteomics, of the 192 differentially expressed proteins,31 additively and 74 non-additively accumulated proteins were observed. The non-additive proteins of the roots of sorghum-sudangrass hybrids was greater contributors to heterosis than additive proteins, overdominant effects was a major factor in non-additive accumulated proteins.7. Functional analysis and bioinformatics analysis of additively and non-additively accumulated proteins of roots of sorghum-sudangrass hybrids indicated that high accumulation levels of ribosomal proteins, modifications of carbohydrates, better stress response systems in hybrid offspring leaded to the accumulation of heterosis of roots of sorghum-sudangrass hybrids.8. We carried out quantitative analysis of proteins in the mature embryo of sorghum-sudangrass hybrids and their parents,124 differentially expressed proteins were observed, additive and non-additive accumulation expression patterns which accounted for 38.71% and 61.29% of differentially expressed proteins, respectively. Non-additive proteins played especially dominant roles in forming heterosis of mature embryo of sorghum-sudangrass hybrids, of the non-additive proteins, overdominant expression pattern(above-high-parent expression, below-low-parent expression) was a dominated factor.9. Additively and non-additively accumulated proteins of mature embryo of sorghum-sudangrass hybrids related to many important functional categories, mainly involved in stress response, carbohydrate metabolism, and protein metabolism. Bioinformatics analysis of hybrid mature embryo also proved that decreased physiological metabolism, lower enzyme activity, enhanced stress response in hybrid was the main cause of heterosis of mature embryo.