Department of Biological, Geological and Environmental Sciences, University of Bologna, Bologna, Italy.
AMAP, Université de Montpellier, IRD, CIRAD, CNRS, INRAE, Montpellier, France.
Ann Bot. 2024 Nov 13;134(5):803-814. doi: 10.1093/aob/mcae115.
Thallium (Tl) is extremely toxic to all life forms and is an emerging pollutant. Plants in the Brassicaceae family, including edible crops, have an enhanced capacity for Tl accumulation, even from soils with low thallium concentration. The most extreme Tl hyperaccumulator is Biscutella laevigata, capable of attaining >32 000 μg Tl g-1 dry weight (DW) in its leaves.
Biscutella laevigata from a non-metallicolous accession (Feltre, Italy) and a metallicolous accession (Les Malines, France) were subjected to a dosing experiment in hydroponics (0, 5 and 30 μm Tl), followed by synchrotron-based micro-X-ray fluorescence analysis to elucidate tissue- and cellular-level Tl distribution.
Flow cytometric data on the two accessions showed that the Feltre accession has a genome size twice of that of the Les Malines accession (256 and 125 pg per 2C, respectively), suggesting that they are phylogenetically distant populations. The Feltre accession did not accumulate Tl (125 μg Tl g-1 DW on average in leaves) at the 5 µm Tl dose level, whereas the Les Malines accession had a mean of 1750 μg Tl g-1 DW, with peaks of 24 130 μg Tl g-1 DW, at the 30 µm Tl dose level. At 30 µm Tl, the non-metallicolous accession did not grow, and at 5 µm Tl it showed reduced biomass compared with the metallicolous one. In the Les Malines accession, the synchrotron-based micro-X-ray fluorescence analysis revealed that Tl was localized in the vacuoles of epidermal cells, especially underneath trichomes and in trichome basal cells. Thallium also occurred in solid crystalline deposits (3-5 µm in size, ~40 wt% Tl) that were found mainly in foliar margins and under trichome bases.
Biscutella laevigata is an attractive model for studying Tl hypertolerance and hyperaccumulation on account of the extreme expression of this trait and its marked intraspecific variability.
铊（Tl）对所有生命形式都具有极强的毒性，是一种新兴污染物。十字花科植物，包括可食用作物，具有增强的 Tl 积累能力，即使在 Tl 浓度较低的土壤中也是如此。最极端的 Tl 超积累植物是 Biscutella laevigata，其叶片中 Tl 的含量可达到>32000μg g-1 干重（DW）。
对来自非金属矿区（意大利费尔特雷）和金属矿区（法国 Les Malines）的 Biscutella laevigata 进行水培（0、5 和 30 μm Tl）剂量实验，然后进行基于同步加速器的微 X 射线荧光分析，以阐明组织和细胞水平的 Tl 分布。
对两个品系的流式细胞术数据表明，费尔特雷品系的基因组大小是 Les Malines 品系的两倍（分别为 256 和 125 pg 2C），表明它们是系统发育上相距较远的种群。费尔特雷品系在 5 μm Tl 剂量水平下不积累 Tl（叶片中平均 125μg g-1 DW），而 Les Malines 品系在 30 μm Tl 剂量水平下的 Tl 含量平均为 1750μg g-1 DW，峰值为 24130μg g-1 DW。在 30 μm Tl 下，非金属矿区的植物无法生长，而在 5 μm Tl 下，其生物量与金属矿区相比有所减少。在 Les Malines 品系中，基于同步加速器的微 X 射线荧光分析表明，Tl 定位于表皮细胞的液泡中，特别是在毛状体下和毛状体基部细胞中。Tl 还存在于固体结晶沉积物中（大小为 3-5 μm，约 40 wt% Tl），主要存在于叶片边缘和毛状体基部下。
Biscutella laevigata 是研究 Tl 超耐性和超积累的理想模型，因为其表现出这种性状的极端表达及其明显的种内变异性。
