Multi-omics analysis of the Cd response mechanism in Iris domestica and the role of IdNRAMP2 in Cd translocation

Iris domestica, a rhizomatous perennial member of the Iridaceae family, exhibits high resistance to various abiotic stressors. However, the molecular mechanisms by which I. domestica faces escalating cadmium (Cd) stress was still unclear. In this study, we investigate the influence of Cd stress on the phenotype, cytology, and multi-omics of I. domestica. Cd stress reduced the contents of photosynthetic pigments, increased the antioxidant enzyme activities, and inhibited plant growth and development. Transport factor analysis revealed that I. domestica processed strong Cd transport capability from the roots to the leaves. Transmission electron microscopy (TEM) revealed that Cd stress damaged the cell ultrastructure in both roots and leaves of I. domestica. Metabolome analysis revealed that 2438 and 2274 metabolites were detected in Cd-treated I. domestica's roots and leaves, respectively. RNA-seq identified 6351 and 2546 differentially expressed genes (DEGs) in roots and leaves of Cd-treated I. domestica, respectively. Conjoint analysis revealed that the DEGs and differentially expressed metabolites (DEMs) were mainly involved in phenylpropanoid metabolism, glutathione metabolism, and plant hormone signal transduction. Furthermore, Cd stress significantly increased the expression levels of transport protein-encoding genes, especially IdNRAMP2. Overexpression of IdNRAMP2 in tobacco and I. domestica promoted the accumulation and root-to-leaf translocation of Cd, and enhaced the activities of the antioxidant enzymes. Our comprehensive, multifaceted investigation offers molecular insights into the response of plants to Cd stress.