Plant Sex Influences Cadmium Detoxification via Mediating Cadmium Transport and Cell Wall Modification Under Different Nitrogen Forms

Although the link between cadmium (Cd) and N availability has been studied, the mechanisms of Cd transport and detoxification in dioecious plants remain underexplored. This study examined sex-specific Cd transport, accumulation, and cell wall detoxification in Populus cathayana using histochemical assays, ecophysiological measures, energy-dispersive X-ray microanalysis, and transcriptomic analyses. Bark accumulated 85% Cd in the shoots of both sexes, while leaf Cd was highest in females under NH₄ ⁺ supply. Root Cd accumulation was greater with NO₃ ^- than NH₄ ⁺, with 40%-60% of Cd sequestrated in cell walls, more so in males. In root cell walls, 60% of Cd was bound to pectin, and 30% was sequestrated in hemicellulose 1. Females sequestrated root Cd by increasing saccharide content, while males enhanced pectin demethylation to bind Cd in cell walls, especially under NO₃ ^- supply. In females under NH₄ ⁺ supply, endogenous nitric oxide (NO) burst decreased root Cd uptake and cell wall accumulation. In males, endogenous NO upregulated the expression of genes related to Cd transport, detoxification, and cell wall biosynthesis. In conclusion, plant sex adjusted their Cd detoxification strategies in response to the changed soil nutrient availability. Understanding the sex-specific detoxification strategies facilitated to the engineering application to remediate heavy metal-contaminated soils.