条斑紫菜中砷的亚细胞分布及其解毒机制的研究

Subcellular Distribution and Mechanism of Detoxifying Arsenic in Porphyra Yezoensis

通过对砷的富集形态变化和亚细胞分布研究,揭示条斑紫菜中砷的区隔化效应及其对砷的解毒机理。将活体条斑紫菜分别暴露于0.05,0.1,0.5和1.0 mg/L的亚砷酸根(AsO33-)和砷酸根(AsO3-)溶液中6 d,每天取样一次,运用HPLC-ICP-MS法分析紫菜中砷的形态变化,运用差速离心技术分析砷在亚细胞水平的分布差异。结果表明,随着介质浓度的升高和暴露时间的增加,藻体中的砷含量呈线性增长趋势,统计分析表明条斑紫菜对As(Ⅲ)和As(Ⅴ)的积累与暴露浓度都呈极显著正相关,相关系数RAs(Ⅲ)=0.99960,p<0.01;R As(Ⅴ)=0.9844,p<0.01;条斑紫菜对As(Ⅲ)的富集速率略高于As(Ⅴ),暴露在0.1 mg/L As(Ⅲ)和As(Ⅴ)溶液中6 d后的富集系数分别是4718.7和4111.5。研究表明,条斑紫菜中砷的亚细胞分布与区隔化差异很大,各组分的砷含量分别为:细胞液80%>细胞壁15%>细胞器5%。藻体胞液是砷的主要储存部位,胞液对砷具有非常明显的区隔化作用。通过对其富集过程中砷形态转化规律的研究发现:As(Ⅴ)会迅速被甲基化,然后再转化成砷糖(AsX1);As(Ⅴ)会迅速被富集还原成As(Ⅲ),As(Ⅲ)被逐步甲基化,然后再转化成砷糖(AsX1)。

In order to disclose the compartmentation of arsenic and the mechanism of detoxifying arsenic in Porphyra yezoensis, the transformation of different arsenic speciation and the subcellular distribution of arsenic in P. yezoensis were conducted. The seaweed was exposed to different concentrations （0.05, 0. 1, 0 5 and 1.0 mg/L） of arsenite （As（）） and arsenate （As（V）） for 6 days. Samples were randomly collected every day. The arsenic speciation in P. yezoensis was analyzed using HPLC-ICP-MS and the subcellular distribution of arsenic was conducted using differential centrifugation. Results showed that the arsenic accumulated in the seaweed increased with the exposed concentration and exposure time increasing. A clear dose-response was proved to exist in both As（I） and As（V） exposure, and the correlation coefficient was 0. 9996 （p〈0.01） and 0.9844 （p〈0.01） for Asf（Ⅲ） and As（V） respectively. In addition, the accumulation rate of As（Ⅲ） was higher than that of As（V）, and the accumulation coefficient of arsenic was 4719 and 4112 respectively for the seaweed exposed to 0. lmg/L As（Ⅲ） and As（V） after 6ds exposure. The results also proved that there was a great difference in the different subcellular distribution and the compartmentation of arsenic in P. yezoensis. The sequcence of different subcellular distribution was cyplasmic supernatant （ 80% ） 〉 cell wall （ 15% ） 〉 cell organelles （5%）. Cyplasmic supernatant was the main localization for arsenic and played an important role in the compartmentation of As. At the same time, the research of the arsenic transformation during accumulation showed that the absorbed As（Ⅲ） in P. yezoensis would be quickly methylated and then be transformed to arsenic sugar （AsX1）; the absorbed As（V） in P. yezoensis would be firstly reduced to As（Ⅲ）, which was then be methylated and transformed to arsenic sugar （ AsX1 ）. The ability of the compartmention and the transformation of different arsenic speciation in P. yezoensis may play a key role in detoxifying arsenic.