Chen Yi-Tze, Lo Jing-Chi, Nozoye Tomoko, Lo Ying-Chu, Hu Chun-Hao, Nishizawa Naoko K, Yeh Kuo-Chen
Agricultural Biotechnology Research Center, Academia Sinica, Taipei, 115, Taiwan.
Department of Horticulture, National Chiayi University, Chiayi, 600, Taiwan.
New Phytol. 2025 Nov;248(3):1268-1283. doi: 10.1111/nph.70522. Epub 2025 Sep 2.
This study investigated the mechanism of nicotianamine (NA) secretion in plants by comparing the zinc/cadmium (Zn/Cd) hyperaccumulator Arabidopsis halleri with Arabidopsis thaliana. NA, a key metal chelator, is secreted into the rhizosphere of A. halleri, but the transporter responsible for this efflux remains unidentified. Transcriptome analysis, quantitative reverse transcription polymerase chain reaction, and NA efflux assays in oocytes were used to identify and characterize candidate transporters. Transgenic A. thaliana lines with altered EFFLUX TRANSPORTER OF NA 1 (ENA1) expression were generated to assess its physiological role. NA secretion and Zn uptake were quantified using UPLC-MS/MS and Zn labeling. Promoter-GUS fusion and in situ hybridization revealed spatial expression. ENA1 was identified as a plasma membrane-localized NA exporter with higher expression in A. halleri and Zn-induced expression only in this species. In A. thaliana, overexpression of ENA1 enhanced NA secretion and reduced Zn accumulation and sensitivity, while knockdown of homologs suppressed NA efflux. These results support a functional role of ENA1 in NA export. ENA1 mediates root-based NA secretion and may contribute to Zn tolerance in hyperaccumulators. Its species-specific regulation and localization suggest an adaptive mechanism for rhizosphere metal management. This discovery advances our understanding of plant metal homeostasis and provides a molecular basis for phytoremediation and biofortification strategies.
本研究通过比较锌/镉（Zn/Cd）超积累植物拟南芥（Arabidopsis halleri）和模式植物拟南芥（Arabidopsis thaliana），探究了植物中烟酰胺（NA）的分泌机制。NA是一种关键的金属螯合剂，可分泌到A. halleri的根际环境中，但负责这种外排的转运蛋白仍未明确。本研究利用转录组分析、定量逆转录聚合酶链反应以及卵母细胞中的NA外排测定，来鉴定和表征候选转运蛋白。构建了改变烟酰胺外排转运蛋白1（ENA1）表达的转基因拟南芥株系，以评估其生理作用。利用超高效液相色谱-串联质谱法（UPLC-MS/MS）和锌标记对NA分泌和锌吸收进行定量分析。启动子-GUS融合和原位杂交揭示了其空间表达模式。ENA1被鉴定为一种定位于质膜的NA外排蛋白，在A. halleri中表达较高，且仅在该物种中受锌诱导表达。在拟南芥中，ENA1的过表达增强了NA分泌，降低了锌积累和敏感性，而其同源基因的敲低则抑制了NA外排。这些结果支持了ENA1在NA输出中的功能作用。ENA1介导基于根的NA分泌，可能有助于超积累植物对锌的耐受性。其物种特异性调控和定位表明了一种根际金属管理的适应性机制。这一发现增进了我们对植物金属稳态的理解，并为植物修复和生物强化策略提供了分子基础。
