超积累植物东南景天体内镉的存储与再分配过程及其调控机制

Heavy metal such as cadmium (Cd) pollution of agricultural soils is a severe problem in China. A better understanding of mechanisms involved in Cd hyperaccumulation in plants facilitates the development of strategies to phytoremediate the polluted soils. Sedum alfredii is a .Cd/Zn hyperaccumulator native to China, but the mechanisms involved in Cd hyperaccumulation in this plant species is far from known. The aim of this study is to investigate the strategies of Cd storage and remobilization in shoots of S. alfredii during its different plant growth stages by using new methodology (Nano-XRF, µ-XAS, LA-ICPMS etc.), combined with isotope tracing and transcriptomic analysis. Mainly, the project will be focused on: 1) Localization and speciation of Cd at tissue, cellular and subcellular levels in roots and shoots of S. alfredii at different growth stages. 2) the characteristics of Cd remobilization from old tissues to new growth and young tissues; 3) the mechanisms involved long-distance transport of Cd mediated by xylem and phloem systems; 4) the effects of CAM, nutrients deficiency and tissue senescence on Cd storage and remobilization in shoots of S. alfredii. The research of this project may help to better understand the highly effective storage and detoxification machinery in shoots of the hyperaccumulator, which allows the survival of the plant species at uniquely high internal metal concentrations, and may facilitate the discovery of remedies for the debilitating effects of metal pollution on human health.

我国农田土壤镉污染严重亟待修复，探明植物地上部对镉的高量存储机制是优化镉污染土壤植物修复技术的关键所在。但以往研究多集中于超积累植物对镉的吸收、转运与解毒机制，有关镉在植物地上部存储过程的主控因子仍不清楚。本项目以我国原生镉超积累植物东南景天为材料，综合运用金属组分布与形态分析技术（XRF、LA-ICPMS、µ-XAS等）、稳定性同位素示踪、高通量测序等先进技术，重点研究不同生长时期东南景天体内镉的存储位点和赋存形态的动态变化规律，镉在地上部从源到库的再分配过程以及镉主要存储场的库源关系，以明确东南景天地上部镉的存储与再分配过程；通过分析东南景天体内镉的长距离运输途径、镉存储与再分配过程的调节因素，进一步剖析植物地上部镉存储与再分配过程的关键调控机制。旨在为深入揭示植物超积累镉的生理生化与分子机制、破解污染土壤植物修复技术改良与优化的关键瓶颈问题奠定理论基础。

我国镉污染土壤量大面广亟需修复，深入阐明植物超量积累镉的生理与分子机制是优化镉污染土壤植物修复技术的关键所在。本项目主要以镉耐性和累积能力差异显著的东南景天镉超积累生态型和非超积累生态型为材料，采用植物生理生化、微X射线荧光（μ-XRF）原位分析、激光捕获显微切割（LCM）、分子生物学等技术相结合的方法，原位解析了超积累东南景天地上部韧皮部在镉的再转运特性及其作用规律，明确了东南景天地上部不同生理年龄及不同组织细胞类型对镉的吸收、转运与再分配过程，并进一步剖析了东南景天地上部储存区和运输区不同类型细胞对镉胁迫的转录组响应，并初步分析了东南景天存储与转运镉的分子机制，同时发现东南景天对镍、铜、锰都具有很强的耐受性，而且钙、锰在调控镉积累中起着重要的作用。此外，进一步验证了钙、锰等养分元素在东南景天吸收、积累与转运镉中的调控作用及其关键机制。项目研究结果已发表6篇SCI收录期刊论文（篇均影响因子>6，4篇IF>6），并投稿SCI期刊论文1篇。项目累计培养博士或硕士研究生5名（已毕业研究生3名），青年学术骨干1名。