From Proplastid to Chloroplast: Understanding Plastid Differentiation in Maize through Microarray and Proteome Analysis

虽然质体以其在光合作用中的作用而闻名，但质体执行几种基本功能，包括激素、氨基酸、脂肪酸、脂质、维生素、核苷酸和次级代谢物的合成。尽管它们起着重要的作用，但对帮助驱动质体分化过程的发育信号知之甚少。为了解决这一重要的农业和生物学问题，我们将利用已开发的基因组和蛋白质组学研究的新工具。广泛的植物基因组序列的可用性，使我们能够确定一组约1500玉米EST序列编码叶绿体靶向蛋白。 通过阵列分析，我们将研究这些基因在玉米两种光合细胞类型（维管束鞘和叶肉）中的表达。 与此同时，我们将使用高灵敏度的质谱技术对预计在质体中积累的估计3,000种蛋白质进行广泛的调查。 蛋白质组学和表达谱数据的生物信息学整合将提供玉米光合质体所利用的转录和翻译控制机制的详细图片。 最后，将构建携带维管束鞘和叶肉细胞特异性标记的转基因植物，以帮助监测分化过程。 这些GFP构建体将允许详细分析维管束鞘和叶肉细胞生物学，并促进一系列玉米质体突变体的分析。 预计该项目将产生一些结果，例如提高对不同质体类型的生化功能的理解，以及对分化过程的新见解。由于几种叶绿体功能与玉米植物的农艺性状直接相关，这些研究将大大提高我们对这一重要作物的理解和工程能力。

Although best known for their role in photosynthesis, plastids perform several essential functions, which include synthesis of hormones, amino acids, fatty acids, lipids, vitamins, nucleotides and secondary metabolites. Despite their essential role, little is known of the developmental signals that help drive the process of plastid differentiation.. To address this important agricultural and biological problem, we will take advantage of new tools that have been developed for genomic and proteomic studies. The availability of extensive plant genome sequences has enabled us to identify a set of approximately 1500 maize EST sequences that encode chloroplast targeted proteins. Through array profiling, we will examine the expression of these genes in the two photosynthetic cell types in maize, the bundle sheath and mesophyll. In parallel, we will initiate a broad survey of the estimated 3,000 proteins predicted to accumulate in plastids using highly sensitive mass spectroscopy techniques. The bioinformatic integration of proteomic and expression profiling data will provide a detailed picture of transcription and translational control mechanisms utilized by the maize photosynthetic plastids. Finally, transgenic plants carrying bundle sheath and mesophyll cell-specific markers will be constructed to help monitor the differentiation process. These GFP constructs will permit a detailed analysis of bundle sheath and mesophyll cell biology and facilitate the analysis of a series of maize plastid mutants. Several results are expected from this project, such as an improved understanding of the biochemical functions of the different plastid types and novel insights into the differentiation process. As several chloroplast functions are directly related to the agronomic performance of the maize plant, these studies will greatly improve our understanding and ability to engineer this important crop plant.