College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou, 310036, China.
Zhejiang Key Laboratory of Organ Development and Regeneration, College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou, 310036, Zhejiang, China.
BMC Plant Biol. 2022 Apr 6;22(1):174. doi: 10.1186/s12870-022-03569-x.
Brassica juncea behaves as a moderate-level accumulator of various heavy metal ions and is frequently used for remediation. To investigate the roles of metal ion transporters in B. juncea, a cation-efflux family gene, BjCET1, was cloned and functionally characterized.
BjCET1 contains 382 amino acid residues, including a signature motif of the cation diffusion facilitator protein family, six classic trans-membrane-spanning structures and a cation-efflux domain. A phylogenetic analysis showed that BjCET1 has a high similarity level with metal tolerance proteins from other Brassica plants, indicating that this protein family is highly conserved in Brassica. BjCET1 expression significantly increased at very early stages during both cadmium and zinc treatments. Green fluorescence detection in transgenic tobacco leaves revealed that BjCET1 is a plasma membrane-localized protein. The heterologous expression of BjCET1 in a yeast mutant increased the heavy-metal tolerance and decreased the cadmium or zinc accumulations in yeast cells, suggesting that BjCET1 is a metal ion transporter. The constitutive expression of BjCET1 rescued the heavy-metal tolerance capability of transgenic tobacco plants.
The data suggest that BjCET1 is a membrane-localized efflux transporter that plays essential roles in heavy metal ion homeostasis and hyper-accumulation.
芥菜（Brassica juncea）表现出对各种重金属离子的中等水平积累特性，常被用于修复。为了研究金属离子转运蛋白在芥菜中的作用，本研究克隆并功能鉴定了一个阳离子外排家族基因 BjCET1。
BjCET1 包含 382 个氨基酸残基，包括阳离子扩散促进蛋白家族的特征基序、6 个经典的跨膜结构域和一个阳离子外排结构域。系统进化分析表明，BjCET1 与其他芸薹属植物的金属耐受蛋白具有很高的相似性水平，表明该蛋白家族在芸薹属中高度保守。BjCET1 在镉和锌处理的早期阶段表达显著增加。在转基因烟草叶片中的绿色荧光检测表明，BjCET1 是一种定位于质膜的蛋白。BjCET1 在酵母突变体中的异源表达提高了酵母细胞对重金属的耐受性，并降低了镉或锌的积累，表明 BjCET1 是一种金属离子转运蛋白。BjCET1 的组成型表达挽救了转基因烟草植株对重金属的耐受性。
数据表明，BjCET1 是一种定位于膜的外排转运蛋白，在重金属离子的稳态和超积累中发挥重要作用。
