Figure 4

Functional analysis of phosphoproteins under drought treatment.

(A) Venn diagram of phosphoproteins from CK, MD and SD samples. (B) GO enrichment analysis of PLSC phosphoproteins upon drought treatment. (C) PLSC phosphoproteins were functionally classified by COG. A, RNA processing and modification; B, Chromatin structure and dynamics; C, Energy production and conversion; D, Cell cycle control, cell division, chromosome partitioning; E, Amino acid transport and metabolism; F, Nucleotide transport and metabolism; G, Carbohydrate transport and metabolism; H, Coenzyme transport and metabolism; I, Lipid transport and metabolism; J, Translation, ribosomal structure and biogenesis; K, Transcription; L, Replication, recombination and repair; M, Cell wall/membrane/envelope biogenesis; O, Posttranslational modification, protein turnover, chaperones; P, Inorganic ion transport and metabolism; R, General function prediction only; S, Function unknown; T, Signal transduction mechanisms; U, Intracellular trafficking, secretion, and vesicular transport; Z, Cytoskeleton. (D) PPI network analysis of proteins determined as DAPs by 2D DIGE and detected as phosphoproteins by protein phosphorylation enrichment analysis. All the nodes represent the COGs of DAPs in the course of drought stress, nodes with yellow background color represent the COGs interaction with βCA1 directly, and blue background color represent the COGs of DAPs that were also identified as phosphoproteins. Nodes with purple background color represent the COGs both interaction with βCA1 directly and that were identified as phosphoproteins. Therefore, four major clusters of interacting proteins were constructed, which included energy metabolism, carbohydrate transport and metabolism, posttranslational modification and no supervised orthologous group.