Cadmium (Cd) is a toxic metal that poses serious threats to human health. Rice is a major source of dietary Cd but how rice plants transport Cd to the grain is not fully understood. Here, we characterize the function of the ZIP (ZRT, IRT-like protein) family protein, OsZIP2, in the root-to-shoot translocation of Cd and intervascular transfer of Cd in nodes. OsZIP2 is localized at the plasma membrane and exhibited Cd 2+ transport activity when heterologously expressed in yeast. OsZIP2 is strongly expressed in xylem parenchyma cells in roots and in enlarged vascular bundles in nodes. Knockout of OsZIP2 significantly enhanced root-to-shoot translocation of Cd and alleviated the inhibition of root elongation by excess Cd stress; whereas overexpression of OsZIP2 decreased Cd translocation to shoots and resulted in Cd sensitivity. Knockout of OsZIP2 increased Cd allocation to the flag leaf but decreased Cd allocation to the panicle and grain. We further reveal that the variation of OsZIP2 expression level contributes to grain Cd concentration among rice germplasms. Our results demonstrate that OsZIP2 functions in root-to-shoot translocation of Cd in roots and intervascular transfer of Cd in nodes, which can be used for breeding low Cd rice varieties.

Carbonate-rich soils limit plant performance and crop production. Previously, local adaptation to carbonated soils was detected in wild Arabidopsis thaliana accessions, allowing the selection of two demes with contrasting phenotypes: A1 (carbonate tolerant, c+) and T6 (carbonate sensitive, c-). Here, A1 (c+) and T6 (c-) seedlings were grown hydroponically under control (pH 5.9) and bicarbonate conditions (10 mM NaHCO 3, pH 8.3) to obtain ionomic profiles and conduct transcriptomic analysis. In parallel, A1 (c+) and T6 (c-) parental lines and their progeny were cultivated on carbonated soil to evaluate fitness and segregation patterns. To understand the genetic architecture beyond the contrasted phenotypes a bulk segregant analysis sequencing (BSA-Seq) was performed. Transcriptomics revealed 208 root and 2503 leaf differentially expressed genes (DEGs) in A1 (c+) vs T6 (c-) comparison under bicarbonate stress, mainly involved in iron, nitrogen and carbon metabolism, hormones, and glycosylates biosynthesis. Based on A1 (c+) and T6 (c-) genome contrasts and BSA-Seq analysis, 69 genes were associated with carbonate tolerance. Comparative analysis of genomics and transcriptomics discovered a final set of 18 genes involved in bicarbonate stress responses that may have relevant roles in soil carbonate tolerance.

Carbonate-rich soils limit plant performance and crop production. Previously, local adaptation to carbonated soils was detected in wild Arabidopsis thaliana accessions, allowing the selection of two demes with contrasting phenotypes: A1 (carbonate tolerant, c+) and T6 (carbonate sensitive, c-). Here, A1 (c+) and T6 (c-) seedlings were grown hydroponically under control (pH 5.9) and bicarbonate conditions (10 mM NaHCO 3, pH 8.3) to obtain ionomic profiles and conduct transcriptomic analysis. In parallel, A1 (c+) and T6 (c-) parental lines and their progeny were cultivated on carbonated soil to evaluate fitness and segregation patterns. To understand the genetic architecture beyond the contrasted phenotypes a bulk segregant analysis sequencing (BSA-Seq) was performed. Transcriptomics revealed 208 root and 2503 leaf differentially expressed genes (DEGs) in A1 (c+) vs T6 (c-) comparison under bicarbonate stress, mainly involved in iron, nitrogen and carbon metabolism, hormones, and glycosylates biosynthesis. Based on A1 (c+) and T6 (c-) genome contrasts and BSA-Seq analysis, 69 genes were associated with carbonate tolerance. Comparative analysis of genomics and trancriptomics discovered 18 candidate genes involved in bicarbonate stress responses. The screening of the knock-out mutants of the candidates suggested that DAO1 (At1G14130), TBL19 (At5G15900), AHH (AT4G20070), JAZ10 (AT5G13220), and INV-E (At5G22510) may have relevant roles in soil carbonate tolerance.