硫素介导对小花南芥铅分布和转运特征及机理研究

Lead is one of the major heavy metal contaminants in the soil in China, with a serious health risk. Transcriptional analysis showed that the ability of enrich lead in native hyperaccumulator plants of Brassica oleracea in Yunnan Pronvince was related to the chelating mechanism of the mercapto compounds. However, Enzymology and Molecular Mechanisms are still not clear how the mercapto compounds influences the Lead Distribution in Arabis alpine L. var. parviflora Franch (a Pb hyperaccumulator). Taking A. alpine as a case, a Potting test will be carried out, at the different level of Lead stress and sulfur treatment. Synchrotron radiation, Real-time fluorescence quantitative PCR and other technologies are used in this test. Through the analysis from the tissue, cellular and subcellular levels,these indicators can be obtain such as lead and sulfur content, morphology, distribution, mercapto compounds glutathione, cysteine, glutamic acid, glycine, metallothionein, cyberin plant content, complexin synthase activity in plant, and the expression of metallothionein gene. The research aims at the relationship between the migration of lead in A. alpine and mercapto compounds, to clear Lead Distribution, MigrationEnzymology and Molecular Mechanisms in A. alpine. In the study, we will construct the sulfur-mediated regulation of thaliana response to lead stress, which can provide a scientific basis for the phytoremediation of Pb-polluted soil with moderate concentration by using A. alpine.

铅是目前我国土壤中主要重金属污染物之一，具有较大的健康风险。转录组分析云南本土超富集植物小花南芥富集铅与巯基化合物螯合机制相关，但小花南芥体内巯基化合物如何实现对铅分布转运的酶学及分子机理尚不清楚。本项目以小花南芥为材料，采用盆栽试验，设置不同浓度的铅胁迫和硫素处理，利用同步辐射，实时荧光定量PCR等技术，对小花南芥从组织、细胞及亚细胞水平中分析铅和硫的含量、赋存形态、分布特征，含硫化合物谷胱甘肽、半胱氨酸、谷氨酸、甘氨酸、金属硫蛋白、植物络合素含量，植物络合素合酶活性，植物络合素合酶和金属硫蛋白基因表达。验证硫素介导下，铅在小花南芥体内分布和迁移规律与巯基化合物的相关性，阐明小花南芥对铅分布和迁移的酶学及分子机制。构建硫素介导下小花南芥对铅胁迫响应的硫素调控理论和技术，为利用小花南芥修复铅污染土壤提供理论科学依据。

本项目通过盆栽实验，外源添加不同浓度硫(S浓度：0、50和100 mg•kg-1)和在铅胁迫下(Pb2+浓度：0、200、400、800和1600 mg•kg-1)，研究小花南芥(Arabis alpina L. var. parviflora Franch)形态特征、地上、地下和木质部、韧皮部Pb和S含量，Pb和S的亚细胞分布特征，抗坏血酸过氧化物酶活性(APX)、谷胱甘肽还原酶活性(GR)、谷胱甘肽含量(GSH)、抗坏血酸含量(AsA)、POD活性、SOD活性、CAT活性以及土壤微生物数量的影响。结果表明：在铅胁迫下，小花南芥株高、叶长、叶宽、根长、生物量逐渐减少，但在硫作用下有所增加。地上部和根系铅含量显著增加。铅主要分布细胞壁，其次为细胞器，可溶组分铅含量最低。硫主要分布在可溶组分，其次为细胞壁，细胞器铅含量最低。硫的添加使得APX活性、GR活性、GSH含量和AsA含量增加，POD活性、SOD活性和CAT活性增强。在铅胁迫下，硫的添加使小花南芥对铅的吸收和耐性能力增强。为探明含硫化合物促进小花南芥富集Pb的机理，采用外源添加不同硫浓度进行盆栽试验，通过测定谷氨酸、半胱氨酸、谷胱甘肽含量及酶活性，揭示超富集植物小花南芥体内含硫化合物对Pb累积特征的影响。结果表明：硫处理促进了小花南芥对Pb的累积，当硫浓度为50 mg•kg-1和100 mg•kg-1时，富集系数大于1，有利于小花南芥对Pb的富集和转运。硫处理增加了小花南芥体内含硫化合物的含量，增强了小花南芥对Pb胁迫的耐性；提高了小花南芥体内含硫化合物中关键酶的活性，促进了含硫化合物的生成，对植株抵御Pb胁迫起重要作用。