Proteomic Analysis Reveals Accompanying Anion‐Dependent Changes of Cadmium Toxicity During <i>Arabidopsis thaliana</i> Development

Cadmium (Cd) is a significant environmental pollutant with widespread detrimental effects on living organisms, making it a frequent subject of laboratory studies. However, different types of Cd salts are used to spike media, often without considering the possibility that accompanying anions may influence the effects of metal cations. Using two commonly used Cd salts, CdSO₄ and CdCl₂, we observed distinct toxicity effects on Arabidopsis thaliana development. On a physiological level, 7-day-old seedlings exposed to 50 µM CdSO₄ had shorter roots than those treated with CdCl₂. Proteomic analysis revealed strong downregulation of proteins involved in microtubule organization and primary cell wall synthesis in the root of plants exposed to CdSO₄. Additionally, these plants exhibited higher Cd uptake from the medium and greater Cd accumulation in the shoot, indicating that the SO₄ ^2-, as an accompanying anion, exacerbates Cd toxicity. These findings highlight the critical but often overlooked role of accompanying anions in modulating the toxic effects of heavy metals on plants.