Cadmium (Cd) is a toxic metal that threatens human health when enriched in crops. NRAMPs are a family of natural macrophage proteins reported to play a key role in Cd transport in plants. In order to explore the gene regulation mechanism of potato under Cd stress and the role of NRAMPs family in it, this study analyzed the gene expression differences of two different Cd accumulation levels in potato after 7 days of 50 mg/kg Cd stress and screened out the key genes that may play a major role in the differential accumulation of Cd in different varieties. Additionally, StNRAMP2 was selected for verification. Further verification showed that the StNRAMP2 gene plays an important role in the accumulation of Cd in potato. Interestingly, silencing StNRAMP2 increased Cd accumulation in tubers but significantly decreased Cd accumulation in other sites, suggesting a critical role of StNRAMP2 in Cd uptake and transport in potatoes. To further confirm this conclusion, we performed heterologous expression experiments in which overexpression of StNRAMP2 gene in tomato resulted in a threefold increase in Cd content, which further confirmed the important role of StNRAMP2 in the process of Cd accumulation compared with wild-type plants. In addition, we found that the addition of Cd to the soil increased the activity of the plant antioxidant enzyme system, and silencing StNRAMP2 partially reversed this effect. This suggests that the StNRAMP2 gene plays an important role in plant stress tolerance, and future studies could further explore the role of this gene in other environmental stresses. In conclusion, the results of this study improve the understanding of the mechanism of Cd accumulation in potato and provide experimental basis for remediation of Cd pollution.

SIMILAR TO RCD-ONE (SRO) family members and transcription factors (TFs) often improve plant antioxidant capacity through interaction and co-regulation and participate in plant resistance to drought and high-salt stress. However, whether SROs are involved in the response to heavy metal stress, especially SRO genes with a specific response and tolerance characteristics to cadmium (Cd) stress, remains unclear. We first identified six SRO genes in the potato genome by PARP and RST domains. Special and conserved StSROs were found, and the spatio temporal tissue-specific expression patterns and co-expression network diagrams of StSROs under the stress of 5 heavy metals were constructed. Second, we identified StSRO6 as a major effector gene (StSRO6-MEG) and StSRO5 as a secondary effector gene (StSRO5-SEG) through a comprehensive analysis. Interestingly, they may hold true for various physiological or stress responses in plants. In addition, using systematic genomics and comparative omics techniques, the key gene StSRO6 that affects the difference in Cd accumulation was discovered, cloned in the low-Cd accumulation “Yunshu 505”, and transformed into the yeast mutant ycf1 for overexpression. The results proved that StSRO6 could confer Cd tolerance. Finally, through transient expression and in vitro culture tests, we hypothesized that StSROs 5/6 are regulated by the transcription factor StWRKY6 and mediates the reactive oxygen species (ROS) system to confer Cd tolerance. These findings offer a new perspective for understanding the mechanisms underlying Cd tolerance in plants, and simultaneously provide clues for the development of biological agents for preventing and controlling Cd migration and transformation.

Land purity is of central importance to crop production. The accumulation of toxic elements in soil seriously affects crop safety. Phytoremediation is a widely used technology to clean soil pollution because of its low cost, simple implementation, and lack of secondary pollution. This investigation includes data from 4787 articles on phytoremediation of heavy metals in soil from the period between 2008 and 2021, acquired from Web of Science databases. VOSviewer was utilized to conduct statistical analysis of countries (regions), institutions, journals, cited literature, and keywords. According to the statistical data, the use of phytoremediation for cleaning soil with heavy metals has matured in recent years, showing a trend of rapid growth. There were also few collaborative studies on this subject between institutions, and China has the most extensive research in this field and, therefore, has the highest number of publications, followed by India and the United States. Publications from Pakistan are very in-depth and have the highest average number of citations. It was discovered that many researchers are now publishing articles on Environmental Science and Pollution Research. Chemosphere was revealed as the most influential journal, whereas The Journal of Hazardous Materials was the most cited. In-depth research on keywords such as metal enrichment, super-enrichment plants, phytoremediation, Cd, Pb, etc. have been conducted by many scientists; however, the research content for different countries was different. The review analysis revealed that in the future it will be possible to breed trees with high heavy metal accumulation, or to use transgenic plants and ornamental plants with high tolerance to prevent and control heavy metal pollution in soil. This paper aims to provide references for scholars in this field and to allow them quick access to summarized knowledge on this topic.