水稻糖分调控因子OsSPR1及其下游基因OsUGP5在维持碳磷平衡中的功能研究

Screening and functional characterization of the genes involved in maintaining phosphate (Pi) homeostasis in crops is prerequisite for maximizing Pi uptake and utilization potential to utilize limited Pi resources sustainably and efficiently. We have isolated two Pi-starvation responsive genes in rice, OsSPR1 (sugar partitioning regulator1) encoding a MYB transcription factor and OsUGP5 encoding a UDP-glucose pyrophosphorylase which catalyzes the reversible production of UDPG (the precursor of sucrose, sulfolipid and cellulose)..We observed that overexpression of OsSPR1 in rice strongly enhanced expression of OsUGP5, decreased sugar and Pi concentration in leaves, while knockdown of OsUGP5 increased starch and Pi concentration, compared with wild-type plants. .In this project, the single and double mutants and overexpression lines of OsUGP5 and OsSPR1 will be used for functional characterization of these two genes in the maintenance of Pi homeostasis and its crosstalk with carbon metabolism. Meanwhile, in vitro protein activity assay, yeast-one-hybrid, electrophoretic mobility shift assay, chromatin immunoprecipitation-PCR/sequencing, transcriptomic and phenotyping analysis will be conducted to dissect the underlying molecular mechanisms. This project can give insight into understanding of Pi and carbon metabolism coordination in plants, it will also provide candidate genes for the breeding of Pi-efficient crops.

实现有限的磷资源高效利用需要充分发挥农作物磷素吸收利用潜力，迫切需要解析作物中参与维持磷稳态基因的功能。申请人前期从水稻中筛选到两个响应磷信号的基因，编码一个MYB转录因子的OsSPR1和编码二磷酸尿苷葡萄糖焦磷酸化酶的OsUGP5。初步结果显示，在低磷条件下，OsSPR1过表达强烈增强OsUGP5基因的表达，降低水稻叶片糖分和磷的浓度，而OsUGP5突变则提高叶片淀粉和磷的浓度。本项目拟利用这两个基因的单、双突变和过表达材料，通过生长发育表型、磷吸收和磷与糖分分配等分析，明确OsSPR1和OsUGP5在维持水稻磷稳态中的功能；通过体外蛋白活性检测、酵母单杂交、凝胶阻滞、染色质免疫沉淀、转录组分析等解析OsSPR1和OsUGP5之间的上下游调控机制，为揭示作物磷和碳代谢途径交互作用提供分子证据，同时为培育磷高效作物提供候选基因。

本项目围绕不同供磷水平下水稻维持碳磷平衡和生长发育的机制，研究了水稻中糖分配调控因子SPR1(Sugar Partitioning Regulator-1)及其编码UDPG焦磷酸化酶基因OsUGP5在维持碳磷平衡中的功能。明确了SPR1是一个缺磷诱导的转录因子并直接调控OsUGP5表达；发现OsUGP5控制水稻体内UGPase酶的活性和蔗糖合成及糖分分配；解析了OsUGP5影响叶片细胞器中无机磷和总磷的分配及其分子机制；发现SPR1受水稻中磷信号中心调控因子OsPHR2的控制并负调控水稻的株高和抗倒伏能力及稻谷产量。与此同时，发现二磷酸腺苷葡萄糖焦磷酸化酶大亚基(OsAGPL1)和小亚基(OsAGPS1)基因在维持水稻碳、氮、磷稳态中起重要作用。.研究结果基本明确了SPR1和OsUGP5以及OsAGPL1/OsAGPS1在维持水稻磷稳态中的功能及其之间的上下游调控机制，为揭示作物磷和碳代谢途径交互作用提供了分子证据，同时也为培育磷高效作物提供了重要的候选基因。