高/低Cd累积苋菜品种金属累积特性与关键转运基因表达的关系

Metal Accumulation and Expressions of Root Two Key Transporter Genes, HMA4 and IRT1, of High/Low Cd-Accumulating Amaranth Cultivars

采用受污染菜园土进行盆栽试验,研究对Cd累积特性不同的苋菜品种(Amaranth mangostanus L.)对金属的吸收差异。白骨小圆叶油苋菜及正泰小圆叶苋菜地上部分Cd含量分别为(0.116±0.007)mg·kg-1和(0.146±0.002)mg·kg-1,台湾白苋菜及红柳叶苋菜地上部分Cd含量分别为(0.210±0.005)mg·kg-1和(0.349±0.026)mg·kg-1,相比而言前两者属Cd低累积品种,后两者属Cd高累积品种。由于红柳叶苋菜与白骨小圆叶油苋菜Cd含量差异最大,可通过测定两者根系IRT1及HMA4基因表达量,以研究高/低Cd累积特性苋菜品种对金属吸收的差异及其与相关转运蛋白的关系。结果显示,苋菜根系共质体Cd与Fe、Pb的吸收呈极显著正相关(P<0.01)。红柳叶苋菜根系原生质体Fe、Cd及Pb含量显著高于白骨小圆叶油苋菜,同时其根系IRT1表达量高于白骨小圆叶油苋菜,表明苋菜根系IRT1基因的较高表达有助于根系从土壤吸收Fe外,可能有助于Cd与Pb的累积。苋菜地上部分Cd与Zn、Fe的吸收呈显著正相关(P<0.05),与Pb、Mn、Ca的吸收呈极显著正相关。红柳叶苋菜地上部分Ca、Fe、Mn、Cd、Pb的含量显著高于白骨小圆叶油苋菜,同时其根系HMA4基因表达量高于白骨小圆叶油苋菜,表明苋菜HMA4基因的较高表达可能有利于苋菜将根系吸收的Cd等金属转运至茎叶。

Metal accumulation in plants may be controlled by their transporter gene expressions. Here a pot experiment was conducted to investigate the differences of metal uptake by edible amaranth cultivars in relation to the expressions of two key transporter genes, HMA4 and IRT1, in roots using garden soil polluted with heavy metals. The expressions of genes IRT1 and HMA4 in root were determined by semi-quantitative PCR method. Cultivars Baiguxiaoyuanye and Zhengtaixiaoyuanye accumulated(0.116±0.007)mg·kg-1 and(0.146±0.002)mg·kg-1(fresh weight)Cd in shoot, but Taiwanbai and Hongliuye contained(0.210±0.005)mg·kg-1 and(0.349±0.026)mg·kg-1(fresh weight)Cd in shoot, respectively. Therefore, the later two are high-Cd accumulating cultivars. Cadmium accumulation in root protoplasts was posi-tively correlated with Fe and Pb(P<0.01). Concentrations of Cd, Fe and Pb in and the expressions of gene IRT1 in root protoplasts of high-Cd accumulating cultivar Hongliuye were significantly higher than those in low-Cd accumulating cultivar Baiguxiaoyuanye. This implied that higher expression of gene IRT1 in root might contribute to Fe uptake by root, as well as Cd and Pb uptake. Cadmium accumulation in shoot was significantly positively correlated with Zn and Fe(P<0.05)and extremely significantly with Pb, Ca and Mn(P<0.01). Concentrations of Cd, Ca, Fe, Mn and Pb in shoot of high-Cd accumulating cultivar Hongliuye and its expression of gene HMA4 were significantly higher than those in low-Cd accumulating cultivar Baiguxiaoyuanye. This suggests that the higher expression of gene HMA4 in root may facilitate Cd and other metals transport from roots to shoots.