拟南芥有机阳离子转运蛋白OCT1参与ABA激素介导的幼苗早期生长的调控机制

Post-germination growth plays important role in plant adaptation. It is coordinately controlled by phytohormones such as ABA and GA as well as environmental factors such as light, temperature and water. During seedling growth arrest mediated by ABA, we have found that OCT1 (Organic Cation Transporter 1) gene expression is dramatically induced. Our previous data also showed that oct1 mutant is relatively insensitive to ABA-mediated seedling growth arrest. This physiological phenotype can be rescued by genetic complementation assay and is not dependent on the transcriptional changes of ABI3 and ABI5. Althrough, substances of AtOCT1 are not clear while its homologues in animal functioning in transporting mutiple-substrates. In order to investigate the function of OCT1 controlling seedling growth in response to ABA signaling, we will test how OCT1 interacts with ABA pathway’s components in the genetic and biochemistry levels and which substrates OCT1 transport directly. Our study will not only increase the knowledge of correlation between hormone signaling and the function of membrane transporters, but also provides the theoretical basis for regulating germination and post-germination growth in agriculture.

种子萌发后进入幼苗早期生长阶段，是植物适应环境的关键转折点之一，此过程受ABA、GA等激素和光、温、水等环境因子的协调控制。在逆境激素ABA介导的幼苗生长抑制过程中，我们发现拟南芥有机阳离子转运蛋白OCT1（Organic Cation Transporter 1）基因被显著诱导表达，oct1突变体呈现幼苗生长抑制减弱的ABA相对不敏感表型，并且突变体表型可以被遗传回补，然而OCT1基因突变并不影响ABA核心组分ABI3和ABI5的转录水平变化。尽管动物同源蛋白具有底物多样性特征，但AtOCT1运输底物目前还不清楚。为了回答OCT1如何响应ABA信号调控幼苗早期生长，我们拟从OCT1与ABA途径核心组分在遗传和生化上的互作，以及OCT1转运底物等方面进行研究。此工作不仅有助于解析激素信号和膜转运蛋白功能之间的关系，而且将为种子萌发和幼苗生长调控奠定一定的理论基础。

植物膜转运蛋白在离子运输、细胞信号转导及逆境应答等方面发挥重要功能。本项目旨在探究膜转运蛋白在激素信号途径及细胞极性生长上的新功能，研究发现一类有机阳离子转运蛋白基因的表达受到ABA信号途径关键转录因子ABI5的直接调控，其功能缺失突变体中因积累多胺而抑制根生长，通过解析膜蛋白的功能将ABA激素和多胺信号途径联系起来；在根毛细胞极性生长调控上，解析了特异的钙离子转运体-钙结合蛋白互作模块调节根毛中钙离子波动及根毛极性延伸的新机理；此外，研究还揭示了植物耐受重金属离子转运调控的表观遗传机理。基于本项目支持的研究结果将为植物中多胺和钙的跨膜转运提供理论基础，还为提高植物耐受重金属离子胁迫提供一定的理论支撑。