Large-scale analysis of phosphorylated proteins in maize leaf.
Phosphorylation is an ubiquitous regulatory mechanism governing the activity, subcellular localization, and intermolecular interactions of proteins. To identify a broad range of phosphoproteins from Zea mays, we enriched phosphopeptides from Zea mays leaves using titanium dioxide microcolumns and then extensively fractionated and identified the phosphopeptides by mass spectrometry. A total of 165 unique phosphorylation sites with a putative role in biological processes were identified in 125 phosphoproteins. Most of these proteins are involved in metabolism, including carbohydrate and protein metabolism. We identified novel phosphorylation sites on translation initiation factors, splicing factors, nucleolar RNA helicases, and chromatin-remodeling proteins such as histone deacetylases. Intriguingly, we also identified phosphorylation sites on several proteins associated with photosynthesis, and we speculate that these sites may be involved in carbohydrate metabolism or electron transport. Among these phosphoproteins, phosphoenolpyruvate carboxylase and NADH: nitrate reductase (NR) which catalyzes the rate-limiting and regulated step in the pathway of inorganic nitrogen assimilation were identified. A conserved phosphorylation site was found in the cytochrome b5 heme-binding domain of NADH: nitrate reductase, suggesting that NADH: nitrate reductase is phosphorylated by the same protein kinase or highly related kinases. These data demonstrate that the pathways that regulate diverse processes in plants are major targets of phosphorylation.
Key Laboratory of Forest Tree Genetic Improvement and Biotechnology, Ministry of Education and School of Forestry, Northeast Forestry University, 26 Hexing Road, Harbin 150040, People's Republic of China.
Ying-Dong
YD
Bi
Hong-Xia
HX
Wang
Tian-Cong
TC
Lu
Xiao-Hui
XH
Li
Zhuo
Z
Shen
Yi-Bo
YB
Chen
Bai-Chen
BC
Wang
D002843:Chromatin / Q000378:metabolism; D018744:DNA, Plant / Q000378:metabolism; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D010766:Phosphorylation; D018515:Plant Leaves / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018749:RNA, Plant / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D003313:Zea mays / Q000235:genetics / Q000378:metabolism*
D002843:Chromatin; D018744:DNA, Plant; D010940:Plant Proteins; D018749:RNA, Plant; D014157:Transcription Factors