转gsh1基因杨增强重金属镉富集的分子生理调控机制

A lot of soil is seriously contaminated by cadmium (Cd) and urgently needs to be remediated. Cd can enter into roots of Populus species and be further transported to aerial parts such as wood, bark and leaf tissues. After harvesting poplar plants, Cd in soil can be removed. γ-glutamylcysteine synthetase is a key gene involved in glutathione biosynthesis. Overexpressing γ-glutamylcysteine synthetase in cytosol of poplar cells, transgenic poplars were obtained. The transgenic poplars showed a greater capacity for Cd accumulation in aerial parts in comparison with the wildtype poplars. However, the molecular and physiological mechanisms remain unknown underlying the greater Cd accumulation in transgenic poplars. To address this question, the transgenic and wildtype poplars will be exposed to 0 or 100 μM Cd2+ for ca. 3 months in a greenhouse. Subsequently, the comparative physiology and transcriptome will be analyzed in transgenics and wildtype poplars. Specifically, the spatial and time dynamics of net Cd2+ fluxes will be investigated in fine roots of transgenics and wildtype poplars. Photosynthesis, growth, concentrations of Cd, and reduced and oxidized glutathione in different tissues will also be analyzed of transgenics and wildtype plants. Furthermore, the transcriptomic regulation will also be determined in fine roots and mature leaves of transgenic and wildtype poplars. The results of this investigation will be published in international peer-reviewed journals. The output of this study will improve our understanding of the physiological and molecular mechanisms underlying the greater capacity of transgenic poplars. The knowledge gained from this study will also help us to develop efficient woody plants for remediating heavy metal polluted soil.

我国部分土壤受镉(Cd)污染严重，急需治理。利用Cd富集能力强的转基因植物修复Cd污染土壤，效果好，备受关注。在杨树细胞中超表达γ-glutamylcysteine synthetase基因，获得了能稳定遗传的转gsh1基因杨。与野生型相比，转gsh1基因杨显著增强了对Cd的吸收和积累，但其分子生理调控机制尚不清楚。本项目拟以转gsh1基因杨和野生型为试材，运用非损伤微测和基因芯片等关键技术，在分析Cd胁迫下杨树不同组织中Cd含量的基础上，以细根对Cd2+吸收的时空动态为切入点，揭示细根对Cd2+的吸收规律。同时，通过比较转录组学研究，全面解析转gsh1基因杨与野生型响应Cd胁迫的转录组调控机制的异同。最终，综合阐明转gsh1基因杨较野生型增强Cd富集的分子生理调控机制。研究成果不仅能丰富和完善重金属污染土壤的"植物修复"理论，还能对抗镉树种的培育有重要指导意义。

我国部分土壤受镉(Cd)污染严重，急需治理。利用Cd富集能力强的转基因林木修复Cd污染土壤，备受关注。与野生型相比，转gsh1基因杨显著增强了对Cd的吸收和积累，但其分子生理调控机制尚不清楚。本项目以转gsh1基因杨和野生型为研究对象，对转基因杨增强重金属Cd富集的生理与转录调控机制进行了较深入的研究，圆满完成了各项研究任务，取得了以下主要结果：.转基因杨树细根根尖对Cd2+的吸收速率显著高于野生型杨树。与野生型杨树不同，转基因杨树细根吸收的Cd主要转运至地上部分的皮、木材和叶中积累。为了解除积累Cd的毒性，转基因杨树中S素和GSH含量较野生型杨树显著增加。.在无Cd胁迫条件下，与野生型杨树相比，转基因杨树细根和成熟叶中分别有660和436个基因显著差异表达。在根中，差异表达基因主要参与离子转运、胁迫响应、蛋白质修饰和RNA调控等生物学过程；其中参与离子转运过程的基因主要有HMA1/2/4/5、NRAMP2、ZIP6和ABC家族成员等与重金属Cd2+等转运有关的基因。在叶中，差异表达基因也主要参与离子转运、信号转导、胁迫响应等生物学过程；其中参与离子转运过程相关的基因主要有HMA1/2/4/5、ABC家族成员和MTPB1等与Cd2+等转运有关的基因。.在Cd胁迫下，与野生型相比，转基因杨树细根和成熟叶中，与离子转运、信号转导、胁迫响应和RNA调控等生物学过程相关的基因，如HMA2/4、NRAMP2、ZIP6，显著上调表达，促使转基因杨树对Cd2+的吸收、转运、解毒和积累。.上述结果表明，转基因杨主要将细根吸收的Cd2+转运至树皮中积累，通过促进合成GSH，使其与Cd2+络合，降低Cd毒性；同时，通过上调表达HMA2、HMA4和NRAMP2等与Cd吸收、转运和解毒有关的基因，促使转基因较野生型杨树富集更多的Cd。.相关研究结果在国内外高水平期刊上发表SCI论文14篇。上述研究成果不仅丰富和完善了重金属污染土壤的“植物修复”理论，还为抗镉树种的培育奠定了坚实的基础。