Bienertia s. chloroplast compartments replica 2 CCCP band1to10

Bienertia sinuspersici performs C4 photosynthesis without Kranz anatomy through subcellular compartmentalization of carbon fixation within individual cells. In this species, central compartment chloroplasts (C) and peripheral chloroplasts (P) collaborate with cytosolic and mitochondrial components in a NAD-ME type C4 cycle. How the two functionally different chloroplast types can develop within individual cells and the mechanism of import of nuclear encoded, plastid targeted proteins are currently unknown. We used 454 sequencing in combination with large scale label-free proteomics to determine the distribution of photosynthesis-related proteins. Subcellular localization of 169 protein was determined through comparison of protein abundance in four different subcellular fractions. 39 out of the 120 chloroplastic proteins showed differential accumulation between the two chloroplast types. Rubisco, RPP regenerative phase and PSII related proteins accumulated in C chloroplasts whereas C4 related proteins and the NDH complex were more abundant in P chloroplasts. Comparison of transit peptides of differential accumulating proteins indicated no obvious sequence homology or similarities in physico-chemical properties between members of the same group. Protein composition analysis of the central compartment indicated that mitochondria and peroxisomes are the only major components besides chloroplasts in this compartment. The combined information from subcellular and developmental protein profiling was used to generate a first draft of the protein machinery involved in single-cell C4 photosynthesis.

波斯盐生草（Bienertia sinuspersici）可通过单个细胞内的碳固定亚细胞区室化实现C4光合作用（C4 photosynthesis），且不依赖克兰兹解剖结构（Kranz anatomy）。该物种的中央区室叶绿体（C）与外周叶绿体（P），结合胞质及线粒体组分，共同构成NAD-苹果酸酶型C4循环（NAD-ME type C4 cycle）。目前，人们对单个细胞内如何形成两种功能迥异的叶绿体类型，以及核编码、质体靶向蛋白的导入机制仍不清楚。本研究结合454测序技术（454 sequencing）与大规模无标记定量蛋白质组学（label-free proteomics），解析光合作用相关蛋白的分布特征。通过比对四种不同亚细胞组分中的蛋白丰度，确定了169种蛋白的亚细胞定位。120种质体蛋白中，有39种在两类叶绿体间存在差异积累。核酮糖-1,5-二磷酸羧化酶/加氧酶（Rubisco）、核酮糖-1,5-二磷酸再生阶段（RPP regenerative phase）相关蛋白以及光系统II（PSII）相关蛋白在中央区室叶绿体中富集；而C4循环相关蛋白与NADH脱氢酶复合体（NDH complex）则在外周叶绿体中含量更高。对差异积累蛋白的转运肽（transit peptides）进行比对分析发现，同一功能类群的蛋白间不存在明显的序列同源性，理化性质也无显著相似性。对中央区室的蛋白组成分析表明，除叶绿体外，线粒体与过氧化物酶体（peroxisomes）是该区域的主要组分。本研究整合亚细胞与发育蛋白组学分析获得的信息，构建了首个单细胞C4光合作用相关蛋白机器的工作草图。