磷酸烯醇丙酮酸羧化酶(PEPC)是C4植物CO2浓缩机制的关键因素。PEPC以多种同工酶存在于同种植物中，其活性、功能、表达调控均可能存在差异。单细胞C4植物需在同一细胞内维持严格生化区隔，其CO2浓缩机制及光合关键酶的调控特性必定与经典C4植物有显著区别。目前对同种C4植物中不同类型（C3和C4型）PEPC同工酶的比较研究鲜见报道。鉴于此，本项目基于目前对植物PEPC的报道，结合本小组对异子蓬C3、C4型PEPC的研究，拟对单细胞C4植物异子蓬PEPC及其同工酶（C3、C4型）开展深入探索，从两种同工酶体外表达、活性及磷酸化差异；不同发育阶段、组织及环境胁迫下同工酶基因的表达、酶活改变；同工酶在转录（启动子功能）和翻译后（磷酸化和泛素化）调控等方面进行比较研究，从而深入理解异子蓬单细胞C4途径PEPC同工酶响应生长发育的调控机制及对环境适应的贡献，并为农作物高光效遗传改良提供科学依据。

Phosphoenolpyruvate carboxylase (PEPC) is the key factor for CO2 concentrating in C4 plant. Plant PEPC exists different isozymes in one individual plant, its activity, function, expression and regulation pattern must be largely different. For single-cell C4 plant species, maintaining strictly spatial biochemical separation within one individual chlorenchyma cell is essential and crucial, its mechanism of CO2 concentrating and the expression and regulation characteristic of the major photosynthetic enzymes must be different with classical C4 species. So far, few has been reported on comparison of different isozymes (such as C3, C4 types) of PEPC in one C4 plant species. Therefore, in the present study, based on the current report on plant PEPC, combining our previous work on C3 and C4 types of PEPC in Suaeda aralocaspica, we plan to explore the function of C3 and C4 types of PEPC in single-cell C4 plant S. aralocaspica from the following aspects: ① Comparison of differences in protein property, enzymatic activity, phosphorylation pattern between C3 and C4 types of isozyme with in vitro protein expression system; ② comparison of changes of gene expression and enzymatic activity between C3 and C4 types of PEPC in different growth stages, tissues, and under various stress conditions; ③ comparison of differences in regulation at transcriptional (promoter function) and post-translational (phosphorylation and ubiquitination) levels between C3 and C4 types of PEPC isozyme. Thus, a better understanding can be achieved with the regulation mechanism of PEPC isozymes responding to growth and development and their contribution to environmental adaptability in single-cell C4 photosynthetic species S. aralocaspica, and it can also provide scientific and theoretical evidence for genetic improvement of crop with high photosynthetic efficiency.