叶绿体起源于内共生的单细胞蓝藻，其在长期的进化过程中结构和分裂机制发生了变化，其中肽聚糖的退化是其明显特征。在细菌肽聚糖生物合成途径中包含10个关键酶，编码这些酶的基因在植物进化过程中发生了水平转移或丢失，有些保存下来的基因功能发生了变化。其中MurE基因的研究发现，小立碗藓和拟南芥的MurE具有不同的功能，小立碗藓的MurE控制叶绿体的分裂，而拟南芥的MurE参与叶绿体的发育。该发现使通过基因功能互补实验调查某一植物的MurE基因及其质体肽聚糖的功能成为可能。本申请项目拟利用苔藓、蕨类、裸子和被子植物的基因组数据，通过肽聚糖合成途径中关键酶基因的保存状况，研究质体肽聚糖在植物中的退化历程。通过与拟南芥及小立碗藓MurE基因的功能互补分析，研究蕨类和裸子植物质体肽聚糖的功能。另外，通过对MurE基因序列的编辑和修饰、结合基因功能互补实验，分析MurE在植物进化过程中基因功能转变的分子机制。

The endosymbiotic theory states that chloroplasts are derived from the original single-cell cyanobacteria, which structure and division mechanism distinctly changed during the evolution history of plants, as well as degradation of plastid peptidoglycan. There are ten key enzymes are involved in peptidoglycan biosynthesis. Some genes encoded the key enzymes for peptidoglycan synthesis horizontally transferred or disappeared, and some conserved genes functionally changed. Characterization of plant MurE genes showed that the MurE genes are conserved in the moss Physcomitrella patens and Arabidopsis thaliana with different functions. PpMurE gene is closely tied to chloroplast division in moss, and AtMurE is related to chloroplast development in A. thaliana. The finds provide a convenience for understanding function of MurE and plastid peptidoglycan in plants by functional complementation with PpMurE and AtMurE. In the project, the evolution history of plastid peptidoglycan will be analyzed by investigating the genes for peptidoglycan synthesis in genomes of bryophyte, pteridophyte, gymnosperm and angiosperm, and the function of MurE and plastid peptidoglycan in pteridophyte and gymnosperm will be investigated by complementation assay with PpMurE and AtMurE. On the other hand, functional transition mechanism of MurE in evolution history will be investigated through edit and modification of MurE sequences and functional complementation experiments. The expected result may provide basis for understanding the mechanism of chloroplast evolution.