Chen Linghua, Huang Yining, Xu Ming, Cheng Zuxin, Zhang Dasheng, Zheng Jingui
FujianAgriculture and Forestry University, Fuzhou Fujian, China.
Jinshan College of Fujian Agriculture and Forestry University, Fuzhou Fujian, China.
PLoS One. 2016 Jul 14;11(7):e0159238. doi: 10.1371/journal.pone.0159238. eCollection 2016.
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.
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.
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.
黑米（Oryza sativa L.）的果皮富含花青素（ACNs），被认为是比白米更健康的选择。先前的研究已对黑米中ACNs的分子种类进行了充分记录；然而，关于黑米籽粒发育过程中ACN生物合成的代谢机制的信息尚不清楚。
本研究的目的是确定在黑米籼稻品种（Oryza sativa L. indica var. SSP）发育过程中参与动态籽粒蛋白质组的代谢途径的变化。采用相对和绝对定量的等压标签（iTRAQ）串联质谱法来鉴定籽粒蛋白质组中有统计学意义的变化。共检测到约928种蛋白质，其中230种在开花后3至20天的5个连续发育阶段中差异表达。在开花后7天和10天观察到差异表达蛋白质的数量最多，包括76种上调蛋白和39种下调蛋白。基因本体的生物学过程分析表明，这230种差异表达蛋白质可分为14个功能组。最大的一组蛋白质与代谢过程相关，可整合到多个生化途径中。具体而言，在ACN生物合成、糖合成和基因表达调控中起作用的蛋白质被上调，特别是从黑米籽粒发育开始及发育过程中。相反，与信号转导、氧化还原稳态、光合作用和氮代谢相关的蛋白质在籽粒成熟过程中表达下降。最后，通过定量实时聚合酶链反应（qRT-PCR）分析验证了8个编码不同代谢蛋白的代表性基因，这些基因在籽粒发育过程中的转录和翻译表达存在差异。
对属于不同功能类别和亚类的代谢相关蛋白质组的表达分析表明，显著上调的蛋白质与类黄酮和淀粉合成有关。另一方面，下调的蛋白质被确定与氮代谢以及其他功能类别和亚类有关，包括光合作用、氧化还原稳态、生育酚生物合成和信号转导。这些结果为黑米中ACN色素产生的表征和理解提供了有价值的新见解。
