拟南芥SDB基因克隆及其参与叶酸代谢调控的分子机理研究

叶酸参与植物一碳代谢及核酸、氨基酸合成等许多重要生物学过程，它的缺乏或代谢稳态的变化会影响植物生长发育。尽管植物叶酸合成代谢较为清楚，但其代谢调控的分子机理鲜有报道。本项目前期工作发现，拟南芥叶酸合成关键酶－叶酰聚谷氨酸加尾酶突变体dfb的叶酸含量和组分发生明显变化，生长发育异常及对低氮胁迫敏感。为深入理解何种生物学途径/因子与DFB互作，我们筛选获得了dfb抑制突变体sdb (suppressor for dfb)，其叶酸含量和表型恢复至野生型水平，说明SDB有效参与了叶酸代谢调控。本项目旨在克隆SDB基因，明确其时空表达模式及蛋白亚细胞定位等分子特征，分析sdb单突变体及过表达植株表型及叶酸代谢变化，阐明SDB生理生化功能，分析SDB与DFB的作用关系，对sdb、dfb进行转录组分析，解析SDB介导的调控途径。以上研究将为深入理解叶酸代谢调控机理及叶酸代谢调控网络构建提供理论基础。

Folates play important roles in regulating several metabolic pathways such as C1 metabolism and the biosynthesis of nucleic acid and amino acid in plants. Folate deficiency and folate homeostasis has great impact on plant growth and development. Up to now the biosynthesis pathways of folate have been extensively investigated, but the molecular mechanism regulating folate metabolism has remained largely unclear. We previosuly identified the Arabidopsis dfb mutant, which is defective in the plastid-localized folylpolyglutamate synthase DFB gene for a key enzyme involved in folate biosynthesis. The dfb mutant had great changes in folate content and folate components and was more sensitive to low nitrogen stress. In order to explore the regulatory mechanisms of DFB function, we screened for dfb mutant supperssors and one of the suppressor, sdb (suppressor for dfb) was identified. Folate content and phenotype were restored to wild type level in the sdb mutant. In this project, SDB gene will be cloned and its expression pattern and protein subcellular location will be characterized. The sdb single mutant and SDB overexpression materials will be obtained, and the relationship of SDB and DFB will be analyzed. Furthermore we will perform transcriptomics analysis of sdb/dfb/wild type to explore its regulatory mechanism on folate metabolism. This study will shed new light on the molecular mechanism of folate metabolism and construction of the folate regulatory network.