ERF转录因子OsAPBP2转录调控水稻叶酸生物合成的分子机理

Plants are the main source of folate for human，but folate content in grain is very low, and needs to be improved. Transcriptional regulatory is one of key factors for the folate synthesis in plants, but the transcriptional regulatory mechanism of plants in folate biosynthesis remains unclear. We screened and identified one ERF transcription factor OsAPBP2 which can regulate the expression of folate biosynthesis key gene OsADCS, and the biosynthesis of folate in rice. The expression of OsADCS is closely related with the biosynthesis of folate in rice, so the above results suggest that OsAPBP2 can regulate folate biosynthesis through regulating the expression of OsADCS in rice. However the molecular mechanism of OsAPBP2 in regulating the expression of OsADCS, and whether OsAPBP2 controls the biosynthesis of folate by regulating the expression of OsADCS, need further studies to illustrate. On the basis of the preliminary results, we plan to further study (1) the key amino acid and nucleotide sites which involves in the interaction between OsAPBP2and OsADCS promoter; (2) the role of OsAPBP2 in the regulatory of expression of OsADCS and biosynthesis of folate in rice; (3) analyze the pathway through which OsAPBP2 can regulate the biosynthesis of folate in rice by the genetic, biochemical and molecular biological methods. We hope to explain the mechanism how OsAPBP2 transcriptionally regulate the biosynthesis of folate in rice.

植物是人体叶酸的主要来源，但作为主粮的谷物中叶酸含量很低，亟待提高。转录调控是植物调节叶酸合成的关键环节，但调控机理还不清楚。申请人课题组筛选并鉴定调控水稻叶酸合成关键基因OsADCS表达的ERF转录因子OsAPBP2。发现OsAPBP2不仅可结合OsADCS启动子，调控OsADCS表达，而且调节水稻叶酸合成。OsADCS表达水平与水稻叶酸合成密切相关，所以上述研究结果表明OsAPBP2可通过调控OsADCS表达调节水稻叶酸合成，但OsAPBP2调控OsADCS表达及其调节叶酸合成的机理还需进一步研究。本申请拟在前期研究基础上，利用遗传、生化和分子生物学的方法，通过研究1.OsAPBP2与OsADCS启动子互作的关键氨基酸和碱基位点；2. OsAPBP2在OsADCS表达和叶酸合成中的功能；3.遗传分析OsAPBP2调控叶酸合成的途径，阐述OsAPBP2转录调控水稻叶酸合成的分子机理。

植物是人体叶酸的主要来源，但作为主粮的谷物中叶酸含量很低。早期研究发现尿苷三磷酸环羟化异构酶(GTPcyclohydrolase I, GCHI)和氨基脱氧分支酸合成酶 (deoxy chorismate synthetase, ADCS) 是植物催化叶酸合成的限速酶，其转录表达水平与植物体内叶酸合成密切相关，但植物转录调控叶酸合成关键酶表达的机理不清楚。申请人前期研究发现ERF转录因子OsAPBP2可以调控水稻叶酸合成关键OsADCS转录，本研究通过分析OsAPBP2的基本特性；分离并鉴定OsAPBP2与OsADCS和OsGCHI1启动子的相互作用；研究OsAPBP2在调控水稻OsADCS表达及叶酸生物合成中的功能，分析OsAPBP2 调控OsADCS表达与调控水稻叶酸合成的关系；分析OsAPBP2对OsGCHI1 (LOC_Os04g56710,尿苷三磷酸环羟化异构酶1) 表达的调控作用。研究发现OsAPBP2可以直接结合OsADCS和OsGCHI1基因启动子，调控水稻叶酸合成关键OsADCS和OsGCHI1转录；另外，对OsAPBP2调控水稻叶酸合成的研发现OsAPBP2对水稻叶片中叶酸含量有显著影响（含量提高2-3倍），但对水稻籽粒中叶酸含量影响不大(过表达后叶酸含量提高50%左右）。这些研究结果表明ERF因子OsAPBP2通过转录激活水稻叶酸合成关键酶基因的表达，提高水稻中叶酸合成。OsAPBP2对水稻不同组织器官（如叶片和籽粒）中叶酸合成的影响不同，表明水稻不同组织器官中叶酸可能被特异性合成调控。提高粮食作物中籽粒的叶酸含量，需要进一步筛选可有效调控籽粒中叶酸合成关键基因表达的新的调控因子