解析根系生物钟响应氮素信号的分子机制

Nitrogen (N) is the most important nutrient for plants. To perceive the external fluctuating availability of both N concentrations and forms, plants have developed complex regulatory transcriptional networks to adapt their lateral root organogenesis. Recently, we uncovered a new mechanism, “root clock”, for plant to pre-pattern lateral roots along the primary axis in the plant model Arabidopsis. This root clock may represent a general mechanism for plants to coordinate primary root growth with root branching in order to optimize the uptake of nutrients from the soil. To access this hypothesis, the oscillating pattern of the root clock in response to altered N conditions in the crop model rice will be determined in this proposed project. Meanwhile, the involvement of auxin transport, biosynthesis, and signaling transduction on regulating root clock for external N signal will also be tested. In addition, we will further investigated the effect of newly identified C-TERMINALLY ENCODED PEPTIDES (CEPs) on root clock and its interaction with auxin signaling. The integration of the data obtained from these experiments will clarify the role of “root clock”, a novel emerging mechanism, in translating the external N signal to developmental signal for root development in rice. It will also provide a foundation for the development of novel strategies to increase the root N acquisition efficiency under N-limited conditions.

植物为了应对土壤中不同氮素形态和浓度的不均匀分布，通常通过复杂的基因调控网络修正其侧根的发生，并提高对有效氮的感应和吸收效率。我们最新发现侧根的发生受根系生物钟 (root clock) 的决定，但氮信号是否通过调控根系生物钟来改变侧根发生尚不清楚。因此，本课题将在拟南芥相关研究的基础上，以水稻为研究对象，探讨根系生物钟对不同氮素信号的响应及发生模式，分析生长素运输、合成和信号转导在介导根系生物钟对氮素信号响应过程中的作用机制。同时，研究C端编码小肽 (CEP) 作为新颖的氮信号响应分子对根系生物钟的调节作用，以及CEP与生长素之间的互作关系。结果将有助于解析氮素信号调控根系发育的分子机制，为提高根系对外源氮素的感应和氮素利用效率及培育氮高效作物提供候选基因和新的技术途径。

该项目探究不同氮素形态和浓度对水稻根系发育/根系生物钟的调控作用，并明确生长素和小肽信号在介导水稻根系响应氮素中的功能和分子机制。截止项目实施期结束，取得以下成效：1）完成不同氮素处理下水稻根系的表型测定，发现不同氮素形态对水稻根系发育的特异调控，且根尖对铵态氮的吸收会导致根尖酸化进而特异诱导根尖的螺旋化；2）证实了根系生物钟调控侧根发生在不同植物物种中具有保守型，氮素抑制水稻根系生物钟发生的频率；3) 结合药理学、分子生物学、遗传学手段研究并证实了生长素合成、信号转导和极性运输参与了氮素对水稻侧根发生和主根伸长的调控；通过测定不同氮素条件下根尖转录组的变化，鉴定了缺氮诱导的碳端编码小肽OsCEP2，并构建组织表达和遗传突变体材料，初步研究了OsCEP2在调控根系响应氮素中的作用。研究结果为提高水稻根系对外源氮素的感应和吸收利用效率提供了分子机制和候选基因。项目实施周期内，在国际权威期刊发表论文7篇；申请国家发明专利2项，申请水稻新品种权1项；培养研究生5人。