Identification And Analysis Of Populus Simonii × P. Nigra Phosphoproteome And Thylakoid Membranes Protein Complexes

Forest, which is the most important terrestrial ecosystem, is the main sustainable resource of human. For more effective use of forest resources and to complete its process of sustainable development, the protein, which is the actor of physiological functions in vivo needs to be intensively researched. But the regulation of many important physiological processes not only by changing the expression of protein species and their abundance can be done, more importantly, depending on those with temporal and spatial distribution of reversible specific post-translational modification. The reversible phosphorylation is the most important and also the most extensive modification form. Therefore, in this study we target Populus (Populus simonii×P. nigra) as experimental material, through combination of TiO2 and SCX enriched phosphorylated peptides method, the protein phosphorylation map of Populus is constructed by mass spectrometry technology. By this means, we have identified 98 phosphoproteins and 114 protein phosphorylation sites form young leaves of Populus proteomics, including 21 Threonine phosphorylation sites and 93 Serine phosphorylation sites. Among the identified phosphorylation sites, there are 104 new discoveried sites which were never reported before, accounting for 91.23% in total identified sites Currently, this is the largest woody plants phosphorylation site database. In addition, we classify phosphorylation sites identificated respectively under the cellar component, molecular function and biological process then make a comprehensive analysis of the distribution of Populus phosphoproteins and physiological processes involved.To better understand the mechanism of photosynthesis of woody plants, this study also identified Populus thylakoid membrane proteins. Application of Blue-native Page gel electrophoresis, we directly dissolved thylakoid membrane protein complexes through specific non-ionic detergent, separated them according to complex size in non-denaturing conditions, and then the constituent subunits of complexs under denaturing conditions. Combining with mass spectrometry there are 45 non-redundant Populus thylakoid membrane protein were identified. Then we classify them according to thylakoid structure and function, there are 15 proteins belonging to PS II,6 proteins belonging to PS I,9 proteins belonging to ATP synthase complex,2 proteins belonging to Cytb6f complex,7 proteins belonging to enzymes involved in carbon dioxide fixation reaction and also 2 unknown proteins,4 proteins with no direct function in photosynthesis. On this basis, we analyze the forms of Populus thylakoid membrane protein complex under physiological conditions and make a foundation for the study of photosynthesis mechanism of woody plants in future.