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Plant natural resistance-associated macrophage protein (NRAMP) plays an important role in maintaining intracellular metal homeostasis and coping with environmental heavy metal stress. Until now, studies on NRAMP in tobacco have been limited. In this study, NtNRAMP1 was cloned from tobacco cultivar TN90, and the highest expression level was observed in the roots, which was strongly induced by Fe deficiency. Heterologously expressed NtNRAMP1 significantly increased the Cd sensitivity of the yeast Δycf1 mutant. Three overexpressed NtNRAMP1 lines were generated to reveal the biofunction of NtNRAMP1. In the soil pot experiments under natural conditions, the contents of Fe and total chlorophyll were increased in the leaves of transgenic tobacco compared with the WT. To reveal the characteristics of NtNRAMP1 in metal transport, transgenic plants were cultured in hydroponic solution with 50 μM Cd and 200 μM Fe. Compared with the WT, the Cd concentrations in transgenic plants increased by 1.26-2.02-fold in the roots. Interestingly, the Cd content in the shoots of transgenic plants was slightly reduced compared with that of the WT. Overexpression of NtNRAMP1 did not promote Fe uptake from the external environment into the roots but enhanced the transfer of Fe from the roots to shoots. Additionally, Fe overload in the leaves of transgenic tobacco resulted in increased levels of MDA and H

The SQUAMOSA promoter binding protein-like (SPL)SPL family genes play an important role in regulating plant growth and development, synthesis of secondary metabolites, and resistance to stress. Understanding of the role of the SPL family in tobacco is still limited. In this study, 42 NtSPL genes were identified from the genome of the tobacco variety TN90. According to the results of the conserved motif and phylogenetic tree, the NtSPL genes were divided into eight subgroups, and the genes in the same subgroup showed similar gene structures and conserved domains. The cis-acting element analysis of the NtSPL promoters showed that the NtSPL genes were regulated by plant hormones and stresses. Twenty-eight of the 42 NtSPL genes can be targeted by miR156. Transcriptome data and qPCR results indicated that the expression pattern of miR156-targeted NtSPL genes was usually tissue specific. The expression level of miR156 in tobacco was induced by Cd stress, and the expression pattern of NtSPL4a showed a significant negative correlation with that of miR156. These results suggest that miR156-NtSPL4a may mediate the tobacco response to Cd stress. This study lays a foundation for further research on the function of the NtSPL gene and provides new insights into the involvement of NtSPL genes in the plant response to heavy metal stress.

Background: Artemisinin is a sesquiterpene lactone compound with a special peroxide bridge that is tightly linked to the cytotoxicity involved in fighting malaria and cancer. Artemisinin and its derivatives (ARTs) are considered to be potential anticancer drugs that promote cancer cell apoptosis, induce cell cycle arrest and autophagy, inhibit cancer cell invasion and migration. Additionally, ARTs significantly increase intracellular Reactive Oxygen Species (ROS) in cancer cells, which result in ferroptosis, a new form of cell death, depending on the ferritin concentration. Ferroptosis is regarded as a cancer suppressor and as well as considered a new mechanism for cancer therapy. Methods: The anticancer activities of ARTs and reference molecules were compared by literature search and analysis. The latest research progress on ferroptosis was described, with a special focus on the molecular mechanism of artemisinin-induced ferroptosis. Results: Artemisinin derivatives, artemisinin-derived dimers, hybrids and artemisinin-transferrin conjugates, could significantly improve anticancer activity, and their IC50 values are lower than those of reference molecules such as doxorubicin and paclitaxel. The biological activities of linkers in dimers and hybrids are important in the drug design processes. ARTs induce ferroptosis mainly by triggering intracellular ROS production, promoting the lysosomal degradation of ferritin and regulating the System Xc-/Gpx4 axis. Interestingly, ARTs also stimulate the feedback inhibition pathway. Conclusion: Artemisinin and its derivatives could be used in the future as cancer therapies with broader applications due to their induction of ferroptosis. Meanwhile, more attention should be paid to the development of novel artemisinin-related drugs based on the mechanism of artemisinininduced ferroptosis.

Tobacco (Nicotiana tabacum L.) is the most important non-food cash crop worldwide and has recently been considered a Cd hyperaccumulator. Metallothionein, a small–molecular weight protein with cysteine-rich domains, plays a key role in plant growth, development, and maintenance of metal homeostasis. The understanding of the tobacco metallothionein (MT) gene family remains unclear. Herein, we systematically characterized twelve NtMT genes in the tobacco genome and classified them into three phylogenetic subfamilies. A number of cis-elements related to plant responses to hormones and abiotic stresses were detected in the promoters of NtMT genes. Tissue expression pattern analysis indicated that NtMT4A/4B were expressed only in seeds, and NtMT2C/2F/2G were mainly expressed in roots. Moreover, most of the NtMT genes were highly induced by heavy metal stress and ion deficiency, suggesting their critical role in relieving metal toxicity and maintaining ion homeostasis in tobacco. This was the first study to describe the genome-wide analysis of the NtMT gene family in tobacco, and the results lay a foundation for understanding the functions of NtMT genes for further enhancing plant tolerance to heavy metal toxicity.