Guo Qiang, Meng Lin, Humphreys Mike W, Scullion John, Mur Luis A J
Beijing Research and Development Center for Grass and Environment, Beijing Academy of Agriculture and Forestry Science, Beijing 100097, PR China.
Beijing Research and Development Center for Grass and Environment, Beijing Academy of Agriculture and Forestry Science, Beijing 100097, PR China.
Plant Physiol Biochem. 2017 Mar;112:270-277. doi: 10.1016/j.plaphy.2017.01.013. Epub 2017 Jan 16.
Heavy metal ATPase 3 (HMA3), a P-ATPase, is a key tonoplast transporter involved in mediating the vacuolar sequestration of cadmium (Cd) to detoxify the intake of this element by plants. HMA3 expression in response to Cd stress has not been previously examined in the grass hybrid species Festulolium loliaceum (Huds.) P. Fourn. In this study, FlHMA3 isolated from F. loliaceum was found to comprise 833 amino acid residues with 77% homology to the rice OsHMA3. Transient expression of FlHMA3 fused to enhanced green fluorescent protein in Arabidopsis protoplasts suggested its localization to vacuolar membranes. Quantitative real-time RT-PCR analysis of F. loliaceum revealed that FlHMA3 is expressed predominantly within roots and up-regulated by excess Cd. Over the 168 h treatment, Cd content of F. loliaceum roots was significantly higher than that of shoots, regardless of external CdCl concentrations. A significant positive correlation was found between FlHMA3 expression and Cd accumulation in roots of F. loliaceum seedlings subjected to 10-100 mg L CdCl for 168 h or, in a separate experiment, to 25 or 100 mg L CdCl for the same duration. These findings provide evidence that FlHMA3 encodes a vacuolar P-ATPase that may play an important role in Cd sequestration into root cell vacuoles, thereby limiting the entry of Cd into the cytoplasm and reducing Cd toxicity.
重金属ATP酶3（HMA3）是一种P型ATP酶，是液泡膜上的关键转运蛋白，参与介导镉（Cd）的液泡隔离，以解除植物对该元素的吸收毒性。此前尚未在禾本科杂交种黑麦草（Festulolium loliaceum (Huds.) P. Fourn.）中研究过HMA3在镉胁迫下的表达情况。在本研究中，从黑麦草中分离出的FlHMA3由833个氨基酸残基组成，与水稻OsHMA3的同源性为77%。在拟南芥原生质体中对与增强型绿色荧光蛋白融合的FlHMA3进行瞬时表达，结果表明其定位于液泡膜。对黑麦草进行定量实时RT-PCR分析发现，FlHMA3主要在根部表达，并受过量镉的上调。在168小时的处理过程中，无论外部CdCl浓度如何，黑麦草根部的镉含量均显著高于地上部分。在接受10-100 mg L CdCl处理168小时的黑麦草幼苗根部，或在另一项实验中接受25或100 mg L CdCl处理相同时间的黑麦草幼苗根部，发现FlHMA3表达与镉积累之间存在显著正相关。这些发现提供了证据，表明FlHMA3编码一种液泡P型ATP酶，该酶可能在将镉隔离到根细胞液泡中发挥重要作用，从而限制镉进入细胞质并降低镉毒性。
