拟南芥AMOS1基因介导的铵胁迫信号传导途径研究

Ammonium (NH4+) is necessary for normal life in most organisms, but is toxic to the cells when excess. Many properties and relevant physiological and genetic mechanisms underlying NH4+ toxicity have been reported in plants, but the process of defensive signaling triggered and transmitted in plants against NH4+ stress is unknown. In this study, we use Arabidopsis ammonium overly sensitive 1(amos1) mutant identified previously in our lab, which defecting chlorophyll accumulation rather than root growth, shoot fresh weight and NH4+ accumulation compared with wild type in response to NH4+ stress, to explore AMOS1-mediated NH4+-dependent signaling pathway by combination of genetics, genomics, bioinformatics and physiological approaches. Firstly, to find the candidate signaling pathway by analyzing the relationship between NH4+ -induced chlorisis and second messages such as ABA and ROS; and AMOS1-mediated NH4+ -dependent regulation network in transcriptional level and the major motif in promoters of these genes. Secondly, to confirm the signaling pathway via external application of the candidate message, analyses of related gene expression and mutants. Furthermore, to construct the AMOS1-overexpressed lines to test whether they can enhance the signaling pathway and tolerance to ammonium stress during chloroplast development? Collectively, this program is designed to reveal AMOS1-mediated ammonium-dependent signaling pathway and the role of AMOS1 in protecting chloroplast development from ammonium stress.

铵是植物生长发育必需的养分离子，但其过量时易造成毒害。目前对高铵影响植物生长发育的特征、相应的生理和分子过程已有一定的认识，但对植物如何感应和传递铵胁迫信号，以启动防御体系抵抗铵胁迫的了解还非常少。本研究以本实验室先前筛选验证的拟南芥叶片黄化而非根系生长，地上部生物量或体内铵平衡的铵超敏感响应突变体amos1为核心材料，应用遗传学，基因组学，生物信息学，生理学手段，研究AMOS1介导的拟南芥对过量铵的分子响应途径与信号传导过程。通过分析amos1的铵诱导黄化表型与主要内源信号物质变化的关系 和AMOS1介导铵响应的主要分子调控途径和关键调控元件，选定相应的候选信号物质或信号途径并深入验证。另外，构建AMOS1过量表达株系并验证其能否增强铵胁迫响应信号的传递及对高铵的抗性。最终揭示AMOS1介导的铵胁迫信号的主要传导途径，以明确AMOS1是如何维持叶绿体正常发育以忍耐铵毒害。

铵是植物生长发育必需的养分离子，但其过量时易造成毒害。目前对高铵影响植物生长发育的特征、相应的生理和分子过程已有一定的认识，但对植物如何感应和传递铵胁迫信号，以启动防御体系抵抗铵胁迫的了解还非常少。本研究分析了AMOS1，一个在高铵条件下调控叶绿体功能的关键基因，介导的拟南芥对过量铵的分子响应途径与信号传导过程。AMOS1是一个定位于质体的蛋白。全基因组核基因转录分析发现铵胁迫响应的大量基因在amos1突变体中表达明显下降，说明定位于质体的AMOS1是调控铵胁迫响应基因表达的关键因子。这也说明存在一条质体反馈调控信号途径调控铵胁迫响应基因的表达。结合生物信息学，药理学和遗传学手段揭示了植物激素脱落酸(ABA)信号 ABA信号是AMOS1依赖的质体反馈信号的一条重要但非唯一的下游信号途径。该研究还进一步探讨了AMOS1依赖的质体反馈信号途径中上游信号，发现质体中活性氧(ROS)是潜在质体信号物质。综上所述，我们提出了AMOS1在高铵条件下调控叶绿体功能的信号传导模式图。AMOS1是目前唯一报道的影响高铵响应基因的转绿表达的遗传因子.