title: iTRAQ-Based Quantitative Proteomics Analysis of Black Rice Grain Development Reveals Metabolic Pathways Associated with Anthocyanin Biosynthesis.
abstract: BACKGROUND
  Black rice (Oryza sativa L.), whose pericarp is rich in anthocyanins (ACNs), is considered as a healthier alternative to white rice. Molecular species of ACNs in black rice have been well documented in previous studies; however, information about the metabolic mechanisms underlying ACN biosynthesis during black rice grain development is unclear.
  
  
  RESULTS
  The aim of the present study was to determine changes in the metabolic pathways that are involved in the dynamic grain proteome during the development of black rice indica cultivar, (Oryza sativa L. indica var. SSP). Isobaric tags for relative and absolute quantification (iTRAQ) MS/MS were employed to identify statistically significant alterations in the grain proteome. Approximately 928 proteins were detected, of which 230 were differentially expressed throughout 5 successive developmental stages, starting from 3 to 20 days after flowering (DAF). The greatest number of differentially expressed proteins was observed on 7 and 10 DAF, including 76 proteins that were upregulated and 39 that were downregulated. The biological process analysis of gene ontology revealed that the 230 differentially expressed proteins could be sorted into 14 functional groups. Proteins in the largest group were related to metabolic process, which could be integrated into multiple biochemical pathways. Specifically, proteins with a role in ACN biosynthesis, sugar synthesis, and the regulation of gene expression were upregulated, particularly from the onset of black rice grain development and during development. In contrast, the expression of proteins related to signal transduction, redox homeostasis, photosynthesis and N-metabolism decreased during grain maturation. Finally, 8 representative genes encoding different metabolic proteins were verified via quantitative real-time polymerase chain reaction (qRT-PCR) analysis, these genes had differed in transcriptional and translational expression during grain development.
  
  
  CONCLUSIONS
  Expression analyses of metabolism-related protein groups belonging to different functional categories and subcategories indicated that significantly upregulated proteins were related to flavonoid and starch synthesis. On the other hand, the downregulated proteins were determined to be related to nitrogen metabolism, as well as other functional categories and subcategories, including photosynthesis, redox homeostasis, tocopherol biosynthetic, and signal transduction. The results provide valuable new insights into the characterization and understanding of ACN pigment production in black rice.
authors.affiliation: FujianAgriculture and Forestry University, Fuzhou Fujian, China.|Jinshan College of Fujian Agriculture and Forestry University, Fuzhou Fujian, China.
authors.forename: Linghua
authors.initials: L
authors.lastname: Chen
authors.affiliation: FujianAgriculture and Forestry University, Fuzhou Fujian, China.|Department of Food and Biology Engineering, Zhangzhou Institute of Technology, Zhangzhou Fujian, China.
authors.forename: Yining
authors.initials: Y
authors.lastname: Huang
authors.affiliation: FujianAgriculture and Forestry University, Fuzhou Fujian, China.|College of Crop Science, Fujian Agriculture and Forestry University, Fuzhou Fujian, China.
authors.forename: Ming
authors.initials: M
authors.lastname: Xu
authors.affiliation: FujianAgriculture and Forestry University, Fuzhou Fujian, China.|College of Crop Science, Fujian Agriculture and Forestry University, Fuzhou Fujian, China.
authors.forename: Zuxin
authors.initials: Z
authors.lastname: Cheng
authors.affiliation: Shanghai Chenshan Plant Science Research Center, Shanghai Chenshan Botanical Garden, Chinese Academy of Sciences, Shanghai, China.|Shanghai Key Laboratory for Plant Functional Genomics and Resources, Shanghai, China.
authors.forename: Dasheng
authors.initials: D
authors.lastname: Zhang
authors.affiliation: FujianAgriculture and Forestry University, Fuzhou Fujian, China.|College of Crop Science, Fujian Agriculture and Forestry University, Fuzhou Fujian, China.
authors.forename: Jingui
authors.initials: J
authors.lastname: Zheng
mesh_terms: D000872:Anthocyanins / Q000032:analysis / Q000096:biosynthesis*; D002853:Chromatography, Liquid; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D013058:Mass Spectrometry; D053858:Metabolic Networks and Pathways / Q000502:physiology; D012275:Oryza / Q000737:chemistry / Q000254:growth & development / Q000378:metabolism*; D040901:Proteomics / Q000379:methods*; D060888:Real-Time Polymerase Chain Reaction; D012639:Seeds / Q000737:chemistry / Q000254:growth & development / Q000378:metabolism*
chemical_list: D000872:Anthocyanins