In situ images of Cd2+ in rice reveal Cd2+ protective mechanism using DNAzyme fluorescent probe

As a common pollutant, cadmium (Cd) poses a serious threat to the growth and development of plants. Currently, there is no effective method to elucidate the protective mechanism of Cd2+ in plant cells. For the first time, we designed a Cd2+ fluorescent probe to observe the adsorption and sequestration of Cd2+ in rice cell walls and vacuoles. Specifically, Cd2+ is blocked by the Casparian strip and electrostatically attracted to hemicellulose, which is abundantly adsorbed and fixed to the cell walls of the endodermis. For Cd2+ that successfully entered the endodermis, one part entered the cells and was compartmentalised and fixed in the vacuoles, while the other part entered the vascular bundles and precipitated in the cell walls of the sclerenchyma through the ion exchange effect. Furthermore, with prolonged exposure to Cd2+, compartmentalised bodies that were strongly labelled by fluorescence gradually appeared in the vacuoles, which were assumed to be a new heavy metal protective mechanism activated by plants in response to continuous Cd2+ exposure. In conclusion, this study provides an innovative and effective method for the detection of adsorption, transportation, and accumulation of Cd2+ in plant tissues, which can be employed for the rapid identification of crops with low Cd accumulation. [Display omitted] •Fluorescent probe for in situ imaging of Cd2+ at subcellular level.•Fluoresce displayed Cd2+ accumulation in cell wall and vacuole.•Continuous Cd2+ stress induced compartmentalized bodies formation.