硫素在杨树富集重金属镉中的作用机理研究

In China, a lot of soil has been contaminated by cadmium (Cd), which urgently needs to be remedied. Some trees have strong capacities to absorb Cd from soil and translocate it to aerial parts. Harvesting aerial parts of these trees can effectively remove Cd from soil. Previous studies have indicated that sulphur (S) can stimulate Cd accumulation in trees, but the underlying physiological and molecular mechanisms remain to be elucidated. In this proposal, we propose to use a fast growing and strong Cd accumulating poplar genotype (Populus deltoides) treated with different levels of S and Cd, and employ physiological and biochemical methods to determine concentrations of S and Cd, and activities of enzymes and levels of S-containing compounds involved in S metabolism in poplars. Levels of reactive oxygen species (ROS), enzymatic and non-enzymatic antioxidants will also been analyzed in poplars exposed to S and/or Cd treatments. Furthermore, significantly differentially expressed microRNAs and their target genes involved in S metabolism and Cd accumulation will be identified and analyzed in S- and/or Cd-treated poplars through microRNAs sequencing in combination with degradome and transcriptome sequencing. As a result, physiological and miRNAs regulation mechanisms underlying roles of S in Cd uptake, translocation and accumulation will be elucidated in poplars exposed to different S levels in combination with Cd treatments. Outputs of this study will provide scientific evidences for roles of S in accumulation of toxic heavy metals in woody plants. Moreover, this study is of significance because results will also present practical technologies for application of S-containing fertilizers in improving toxic heavy metal accumulation in trees.

我国许多土壤受镉(Cd)污染严重，急需治理。利用Cd富集能力强的林木能有效修复Cd污染土壤。硫(S)素能促进林木对土壤Cd的积累与解毒，但其作用机理尚不清楚。本项目拟以快速生长且对Cd积累能力较强的杨树（Populus deltoides）为试材，采用miRNAs测序技术联合降解组与转录组测序等关键技术，以杨树在不同S素营养和Cd胁迫下的S、Cd含量为切入点，分析杨树中的S素代谢及其在Cd处理下的氧化胁迫与解毒作用，揭示S素在杨树富集Cd中的生理调节规律。同时，通过miRNAs测序联合降解组和转录组测序分析，解析S素和/或Cd处理条件下杨树中的miRNAs调控网络。最终，综合阐明S素在杨树富集Cd中的生理调节规律与miRNAs调控机理。研究成果可为S素在林木积累有毒重金属中的作用提供科学依据；而且还将为应用S素肥料提高林木对重金属污染土壤的修复效果提供适用技术，具有重要实践意义。

我国许多土壤受镉(Cd)污染严重，急需治理。利用Cd富集能力强的林木能有效修复Cd污染土壤。硫(S)素能促进林木对土壤Cd的积累与解毒，但其作用机理尚不清楚。本项目以快速生长且对Cd积累能力较强的杨树（Populus deltoides）为研究对象，对硫素在杨树富集重金属镉中的作用机理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：.Cd处理导致杨树各组织中的Cd浓度显著增加。低S供给使根中的Cd含量升高，高S处理显著增加了杨树地上部分的Cd浓度，而低S导致杨树地上部分的Cd含量降低。中等S素供给条件下，Cd胁迫导致杨树根和皮中的S含量显著降低；高S供给则消除了Cd胁迫的这种影响，并使根、皮和叶中的S含量增加。在中S供给条件下，Cd胁迫引起了根中Cys浓度降低，而高S供给则消除了这种影响。在中S水平时，Cd胁迫引起皮中γ-ECS的活性降低；低S供给加重了Cd的抑制作用，而高S处理则缓解了这一效应。Cd胁迫显著增加了中S供给下杨树根中的H2O2含量，低S处理加重了这一效应，而高S则消除了Cd的这一影响。.在S素和/或Cd处理条件下，共发现了1397个显著差异表达的miRNA。共有845个靶基因与488个miRNA对应，其中347个为已知的miRNA，对应了644个靶基因；还发现了141个未被报道的miRNA与329个靶基因对应。在显著差异表达的77对miRNA-靶基因中，发现4对呈现负相关关系的miRNA-靶基因，分别以核心基因APS3和NF-YA2建立了miRNA调控网络。.上述研究结果表明，杨树中Cd的积累与S素同化都受到低S的抑制而得到高S供给的促进；同时，Cd毒性被低S加重而被高S缓解；miRNA-mRNA调控网络在S介导的Cd积累与解毒过程中起关键作用。.相关研究结果发表SCI论文12篇。上述研究成果不仅为S素促进林木积累有毒重金属提供科学依据，还为应用S肥提高林木修复效率奠定了坚实的基础。