Soil cadmium (Cd) pollution threatens food safety. This study aimed to identify genes related to Cd accumulation in rice. Low-(Shennong 315, short for S315) and high-(Shendao 47, short for S47) Cd-accumulative rice cultivars were incubated with CdCl 2 •2.5H 2 O. RNA-seq and weighted gene coexpression network analysis (WGCNA) were performed to identify the modules and genes associated with Cd-accumulative traits of rice. After Cd stress treatment, the Cd content in various tissues of S315 was significantly higher than that of S47. In the stem nodes, the Cd distribution results of the two varieties indicated that the unelongated nodes near the root (short for node A) had a stronger ability to block Cd transfer upwards than the panicle node (short for node B). Cd stress induced huge changes in gene expression profiles. After analyzing the differentially expressed genes (DEGs) in significantly correlated WGCNA modules, we found that genes related to heavy metal transportation had higher expression levels in node A than that in node B, such as Copper transporter 6 (OS04G0415600), Zinc transporter 10 (OS06G0566300), and some heavy-metal associated proteins (OS11G0147500, OS03G0861400, and OS10G0506100). In the comparison results between S315 and S47, the expression of chitinase (OS03G0679700 and OS06G0726200) was increased by Cd treatment in S315. In addition, OsHSPs (OS05G0460000, OS08G0500700), OsHSFC2A (OS02G0232000), and OsDJA5 (OS03G0787300) were found differentially expressed after Cd treatment in S315, but changed less in S47. In summary, different rice varieties have different processes and intensities in response to Cd stress. The node A might function as the key tissue for blocking Cd upward transport into the panicle via vigorous processes, including of heavy metal transportation, response to stress, and cell wall. Heavy metal cadmium (Cd) contaminates a large area of rice (Oryza sativa), which is one of the largest food crops in China and worldwide 1. Cd pollution causes irreversible soil problems in China. Various technologies and great efforts have been made in the treatment of Cd pollution and restoration of Cd contaminated soils, but the little effect has been achieved. Screening and breeding for low Cd-accumulative cultivars could relieve Cd-induced pressure in cropping system 2,3. Many plant species with low cadmium accumulation have been proposed and widely promoted in scientific research and cropping 2,4. Consequently, identifying genetic targets that can be used to reduce cadmium accumulation in crops is important for plant breeding 5-8. Many genes related to Cd stress have been identified. For instance, the expression of Arabidopsis PLANT DEFENSIN 2 (AtPDF2.5) can promote Cd accumulation in Arabidopsis roots 5. Tang et al. reported that the knockout of OsNramp5 (a magnesium ion (Mg2+) and Cd transporter and a Mn and Cd uptake gene) in rice reduced the accumulation of Cd in rice 8. The comparative transcriptome analysis of low and high Cd accumulation genotypes has been performed on Brassica Chinen...
