洋葱果聚糖外切水解酶(AcFEH)调控果聚糖代谢的分子机理研究

Fructan exohydrolase (FEH) is a key enzyme in plant fructan-metabolic regulation, its molecular mechanisms were unclear. As one of the high-fructan plants, onion's fructan molecular research was rarely reported. Based on our previous study, an onion fructan exohydrolase gene (named AcFEH) was cloned and functionally identified, overexpression of AcFEH could significantly reduce the fructan accumulation, indicating that AcFEH involved in onion fructan metabolism. However, the specific regulatory mechanisms need to be further studied. This project will research on: AcFEH promoter separation, transcription factors screening and identification, promoter and transcription factor binding assay; AcFEH interactive proteins screening and functional identification. Overall, this study will clarify the AcFEH regulated molecular mechanism and signal network in onion fructan metabolism, and will provide a theoretical support for quality improvement in onion and other vegetables through genetic breeding.

果聚糖外切水解酶是植物体内调控果聚糖代谢的关键酶，其分子调控机制仍不清楚。洋葱是果聚糖大量积累的代表性植物之一，迄今对于洋葱果聚糖的分子研究报道很少。本项目在前期研究基础上，获得了一个洋葱果聚糖外切水解酶基因（命名为AcFEH）并进行了蛋白功能验证，过量表达该基因显著降低洋葱球茎中果聚糖的含量，表明其参与调控果聚糖的代谢，但具体调控机理还需深入研究。因此，本项目以AcFEH为切入点，主要开展以下研究：分离启动子，筛选、鉴定与该基因发生作用的转录因子，开展启动子与转录因子结合研究；筛选AcFEH关键互作蛋白并进行功能验证。研究结果旨在阐明洋葱AcFEH调控的果聚糖代谢的分子机理和信号网络，为开展洋葱及其他蔬菜品质改良基因工程研究提供理论支持。

果聚糖外切水解酶是植物体内调控果聚糖代谢的关键酶，其分子调控机制仍不清楚。洋葱是果聚糖大量积累的代表性植物之一，迄今对于洋葱果聚糖的分子研究报道很少。本项目筛选了富含果聚糖的洋葱基因型，进而分析了洋葱鳞茎中的果聚糖组分在贮藏过程含量的变化，明确了洋葱果聚糖外切水解酶基因（命名为AcFEH）的确参与了洋葱鳞茎贮藏过程中果聚糖的降解。对AcFEH进行了蛋白功能验证，过量表达该基因显著降低洋葱球茎中果聚糖的含量，表明其参与调控果聚糖的代谢。通过胁迫研究发现，镉胁迫可抑制洋葱中FOS的积累，伴随着上调洋葱AcGCL基因；镉处理下过量表达AcGCL改善了Cd对洋葱FOS代谢的毒害，这与增加FOS合成有关。通过分离AcFEH启动子，筛选、鉴定与该基因发生作用的转录因子，开展了启动子与转录因子结合研究，发现转录因子bHLH能够调控AcFEH的转录。最后，我们也初步对洋葱果聚糖合成酶6G-FFT的蛋白功能鉴定和晶体展开了研究。这些研究结果旨在阐明调控洋葱A果聚糖代谢的分子机理和信号网络，为开展洋葱及其他蔬菜品质改良基因工程研究提供理论支持。