叶用芥菜镉污染预防品种吸收转运镉的生理机制及转录组分析

Soil cadmium (Cd) contamination has caused a serious threat to food safety. Production of Cd pollution-safe cultivars (PSCs) is an important approach to ensure the safety of agricultural products, and further studies on mechanisms of Cd accumulation between cultivars are indispensible. Based on previous researches on identification of a Cd-PSC (YXZ) and a high-Cd cultivar (JTN) of leaf mustard, this project will investigate the physiological and molecular mechanisms of low Cd accumulation in YXZ. Research contents include: 1. rhizospheric biology characteristics of YXZ and JTN; 2. physiological mechanisms of Cd uptake and translocation in YXZ and JTN; 3. transcriptome analysis of Cd exposure response in YXZ and JTN. The differences, including root morphology, rhizosphere secretions, rhizosphere soil Cd chemical forms, rhizosphere soil cation exchange capacity, rhizosphere microbes, Cd subcellular distribution, transport of Cd via xylem, gene expression under Cd exposure, will be investigated among YXZ and JTN. The implementation of this project will lay a theoretical foundation for breeding Cd-PSCs, and is beneficial to ensure the normal agricultural production and control plant-derived foods contamination by Cd.

土壤和农作物镉（Cd）污染对食物安全造成了严重威胁，选用可食部位低积累Cd的农作物Cd污染预防品种进行农业生产是保障农产品安全的重要途径，而深入开展农作物品种间Cd积累差异的机理研究是培育Cd污染预防品种的首要基础。本项目以叶用芥菜Cd污染预防品种（YXZ）和高Cd品种（JTN）为研究对象，探讨低积累Cd的吸收、转运和分子遗传机理。主要研究内容包括：1. YXZ和JTN的根际生物学特征；2. YXZ和JTN吸收转运Cd的生理机制；3. YXZ和JTN的转录组分析。从根系形态、根际分泌物、根际土壤Cd化学形态、根际土壤阳离子交换量、根际微生物、Cd的亚细胞分布、Cd在植物体内的转运以及Cd诱导基因表达等方面比较YXZ和JTN间的差异，从而阐明YXZ低积累Cd的机理。本项目实施可为发展定向培育Cd污染预防品种的育种技术奠定理论基础，有利于在保障正常农业生产的同时有效预防土壤Cd对农作物的污染。

本项目以前期筛选获得的叶用芥菜Cd污染预防品种（YXZ）和高Cd品种（CYC）为研究对象，阐明Cd污染预防品种低量积累Cd的生理生化与分子机制。研究发现，Cd胁迫下，YXZ的根尖数较少，根长较短，根比表面积较小，这可能减少了根向茎叶转运Cd。虽然根系分泌的低分子量有机酸总量在品种间无显著差异，但是，Cd胁迫下，根系分泌的乙酸在YXZ显著低于CYC。此外，两品种间根际土壤可交换态Cd含量、阳离子交换量以及微生物群落多样性并无显著差异。木质部中Cd的转运分析显示，CYC能更快地将Cd从根通过木质部向地上部转运。YXZ根细胞壁和液泡区隔Cd的能力较CYC高，且醇溶态 Cd在YXZ根中所占的比例明显低于CYC，这可能是YXZ中Cd从根向茎叶转运率低的主要原因。转录组测序结果显示，Cd胁迫下，YXZ根中PDR8和HMA3的表达水平较CYC高。因此，叶用芥菜茎叶Cd含量的高低取决于Cd从根向茎叶的转运效率。