PPT1的功能演化及其在C4植物进化中的作用机制研究

The molecular mechanisms of C4 plant evolution are very important for both theoretical and applied studies, and have attracted wide attention in plant area for a long time. Numerous evidences support that the C4 evolution from C3 plant requires turnover of flux direction of phosphoenolpyruvate (PEP), the key metabolite for C4 plant, but it remains unknown what variation in which gene is responsible for the change. It has been proven that PEP/phosphate translocators PPT1 and PPT2 are responsible for import of PEP from cytosol into chloroplast in C3 plant cells, while PPT1 was suggested to export PEP from chloroplast to cytosol. Plants of the genus Flaveria are good materials for studying C4 photosynthesis evolution because this small genus contains all types of photosynthesis from typical C3 to typical C4 including various intermediates. We assembled PPT1 coding sequences of 16 species of the genus Flaveria by taking advantages of bioinformatics, and found that there are various variations, including a large insertion, among PPT1 coding sequence from different species. Most importantly, we revealed that the sequence variation of PPT1 and its expression level are consistent with the differentiation of C4 and C3 photosynthesis. In this project, we plan to employ multiple strategies, including molecular biology, biochemistry, cell biology, plant biology and evolution biology techniques, to establish the molecular and genetic basis underlying the transition of physiological function of PPT1 and the molecular mechanisms of C4 plant evolution, based on three systems of bacteria, Arabidopsis and Flaveria plants.

C4植物演化的分子机制因其重要的理论意义和应用价值，长期为植物学领域关注。大量证据表明，由C3到C4的演化需完成C4途径关键代谢物PEP流向的转变，然而何种基因何种变异导致的这种转变仍然未知。C3植物细胞中PEP由PEP/磷酸盐转运蛋白PPT1和PPT2从细胞质运输到叶绿体，而C4植物叶肉细胞细胞质所需大量PEP可能由PPT1同源蛋白从叶绿体内运输而来。黄顶菊属植物因其包含从C3到C4所有光合类型的物种被称为C4植物演化的优良材料。我们利用生物信息学拼接组装了16种黄顶菊属植物的PPT1编码序列，发现不同黄顶菊PPT1之间存在包括大片段插入在内的多种自然变异，且这些序列变异和其表达丰度与C3/C4植物的分化高度一致。本项目拟利用细菌、拟南芥和黄顶菊三种研究系统，通过分子生物学、细胞生物学、植物生理学及进化生物学等多种手段阐明PPT1生理功能转化的分子遗传基础及C3/C4植物演化的分子机制。