Institut de recherche en biologie végétale, Département de sciences biologiques, Université de Montréal, 4101 Sherbrooke Est, Montréal, QC H1X 2B2, Canada.
Environmental Genomics and Systems Biology, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
J Exp Bot. 2024 Sep 27;75(18):5897-5908. doi: 10.1093/jxb/erae272.
Arsenic (As) contamination of soils threatens the health of millions globally through accumulation in crops. While plants detoxify As via phytochelatin (PC) complexation and efflux of arsenite from roots, arsenite efflux mechanisms are not fully understood. Here, white lupin (Lupinus albus) was grown in semi-hydroponics, and exudation of glutathione (GSH) derivatives and PCs in response to As was measured using LC-MS/MS. Inhibiting synthesis of the PC precursor GSH with l-buthionine sulfoximine (BSO) or ABC transporters with vanadate drastically reduced (>22%) GSH derivative and PC2 exudation, but not PC3 exudation. This was accompanied by As hypersensitivity in plants treated with BSO and moderate sensitivity with vanadate treatment. Investigating As-PC complexation revealed two distinct As-PC complexes, As bound to GSH and PC2 (GS-As-PC2) and As bound to PC3 (As-PC3), in exudates of As-treated lupin plants. Vanadate inhibited As-PC exudation, while BSO inhibited both the synthesis and exudation of As-PC complexes. These results demonstrate a role for GSH derivatives and PC exudation in lupin As tolerance and reveal As-PC exudation as a new potential mechanism contributing to active As efflux in plants. Overall, this study uncovers insights into rhizosphere As detoxification with potential to help mitigate pollution and reduce As accumulation in crops.
砷（As）污染土壤会通过在作物中的积累而威胁到全球数百万人的健康。虽然植物通过植物螯合肽（PC）络合和根中亚砷酸盐的外排来解毒 As，但亚砷酸盐外排机制尚未完全了解。在这里，白 Lupinus albus 在半水培中生长，并用 LC-MS/MS 测量响应 As 时 GSH 衍生物和 PCs 的分泌。用 l-buthionine sulfoximine (BSO) 抑制 PC 前体 GSH 的合成或用钒酸盐抑制 ABC 转运体，大大降低了（>22%）GSH 衍生物和 PC2 的分泌，但不降低 PC3 的分泌。这伴随着 BSO 处理的植物中 As 的超敏性和钒酸盐处理的中度敏感性。研究 As-PC 络合物发现，在 As 处理的 Lupinus albus 植物的分泌物中存在两种不同的 As-PC 络合物，As 与 GSH 和 PC2（GS-As-PC2）结合以及 As 与 PC3（As-PC3）结合。钒酸盐抑制 As-PC 的分泌，而 BSO 抑制 As-PC 络合物的合成和分泌。这些结果表明 GSH 衍生物和 PC 分泌在 Lupinus albus 对 As 的耐受性中起作用，并揭示了 As-PC 分泌作为一种新的潜在机制，有助于植物中主动的 As 外排。总的来说，这项研究揭示了根际 As 解毒的新见解，有可能有助于减轻污染并减少作物中 As 的积累。
