Laboratory of Genetics, Wageningen University and Research, Wageningen, The Netherlands.
Centre for Mined Land Rehabilitation, Sustainable Minerals Institute, The University of Queensland, Brisbane, Queensland, Australia.
Ann Bot. 2023 Oct 18;132(2):349-361. doi: 10.1093/aob/mcad110.
Selenium hyperaccumulator species are of primary interest for studying the evolution of hyperaccumulation and for use in biofortification because selenium is an essential element in human nutrition. In this study, we aimed to determine whether the distributions of selenium in the three most studied hyperaccumulating taxa (Astragalus bisulcatus, Stanleya pinnata and Neptunia amplexicaulis) are similar or contrasting, in order to infer the underlying physiological mechanisms.
This study used synchrotron-based micro-X-ray fluorescence (µXRF) techniques to visualize the distribution of selenium and other elements in fresh hydrated plant tissues of A. racemosus, S. pinnata and N. amplexicaulis.
Selenium distribution differed widely in the three species: in the leaves of A. racemosus and N. amplexicaulis selenium was mainly concentrated in the pulvini, whereas in S. pinnata it was primarilylocalized in the leaf margins. In the roots and stems of all three species, selenium was absent in xylem cells, whereas it was particularly concentrated in the pith rays of S. pinnata and in the phloem cells of A. racemosus and N. amplexicaulis.
This study shows that Astragalus, Stanleya and Neptunia have different selenium-handling physiologies, with different mechanisms for translocation and storage of excess selenium. Important dissimilarities among the three analysed species suggest that selenium hyperaccumulation has probably evolved multiple times over under similar environmental pressures in the US and Australia.
硒超积累物种是研究超积累进化和用于生物强化的主要对象,因为硒是人类营养中的必需元素。在这项研究中,我们旨在确定三种研究最多的超积累分类群(黄芪、扁果菊和沼生半边莲)中硒的分布是否相似或相反,以便推断潜在的生理机制。
本研究使用基于同步加速器的微 X 射线荧光(µXRF)技术,可视化了黄芪、扁果菊和沼生半边莲新鲜水合植物组织中硒和其他元素的分布。
在这三种物种中,硒的分布差异很大:在黄芪和沼生半边莲的叶子中,硒主要集中在叶枕中,而在扁果菊中,硒主要集中在叶缘。在所有三种物种的根和茎中,木质部细胞中不存在硒,而在扁果菊的髓射线和黄芪和沼生半边莲的韧皮部细胞中,硒特别集中。
本研究表明,黄芪、扁果菊和沼生半边莲具有不同的硒处理生理学特性,具有不同的过量硒转运和储存机制。在这三种分析物种之间存在重要的差异,表明在类似的环境压力下,硒的超积累可能已经在北美和澳大利亚多次进化。