title: Phosphoproteomic identification and phylogenetic analysis of ribosomal P-proteins in Populus dormant terminal buds.
abstract: To better understand the role that reversible phosphorylation plays in woody plant ribosomal P-protein function, we initiated a phosphoproteomic investigation of P-proteins from Populus dormant terminal buds. Using gel-free (in-solution) protein digestion and phosphopeptide enrichment combined with a nanoUPLC-ESI-MS/MS strategy, we identified six phosphorylation sites on eight P-proteins from Populus dormant terminal buds. Among these, six Ser sites and one Thr site were identified in the highly conserved C-terminal region of eight P-proteins of various P-protein subfamilies, including two P0, two P1, three P2 and one P3 protein. Among these, the Thr site was shown to be novel and has not been identified in any other organisms. Sequence analysis indicated that the phosphothreonine sites identified in the C-terminus of Ptr RPP2A exclusively occurred in woody species of Populus, etc. The identified phosphopeptides shared a common phosphorylation motif of (S/T)XX(D/E) and may be phosphorylated in vivo by casein kinase 2 as suggested by using Scansite analysis. Furthermore, phylogenetic analysis suggested that divergence of P2 also occurred in Populus, including type I and type II. To the best of our knowledge, this is the first systematic phosphoproteomic and phylogenetic analysis of P-proteins in woody plants, the results of which will provide a wealth of resources for future understanding and unraveling of the regulatory mechanisms of Populus P-protein phosphorylation during the maintenance of dormancy.
authors.affiliation: Education Ministry Key Laboratory of Forest Tree Genetic Improvement and Biotechnology, Northeast Forestry University, 26 Hexing Road, 150040 Harbin, People's Republic of China.
authors.forename: Chang-Cai
authors.initials: CC
authors.lastname: Liu
authors.forename: Tian-Cong
authors.initials: TC
authors.lastname: Lu
authors.forename: Hua-Hua
authors.initials: HH
authors.lastname: Li
authors.forename: Hong-Xia
authors.initials: HX
authors.lastname: Wang
authors.forename: Gui-Feng
authors.initials: GF
authors.lastname: Liu
authors.forename: Ling
authors.initials: L
authors.lastname: Ma
authors.forename: Chuan-Ping
authors.initials: CP
authors.lastname: Yang
authors.forename: Bai-Chen
authors.initials: BC
authors.lastname: Wang
mesh_terms: D000595:Amino Acid Sequence; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000737:chemistry / Q000235:genetics*; D010766:Phosphorylation; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics*; D032107:Populus / Q000235:genetics* / Q000378:metabolism; D040901:Proteomics; D012269:Ribosomal Proteins / Q000737:chemistry / Q000235:genetics*; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein
chemical_list: D010750:Phosphoproteins; D010940:Plant Proteins; D012269:Ribosomal Proteins