Tobacco (Nicotiana tabacum) is a cadmium (Cd) accumulator, and smoking is a major source of Cd exposure. In the present study, we identified two tobacco cultivars with contrasting phenotypes of Cd and manganese (Mn) accumulation in both hydroponic and soil pot experiments. Physiological experiments showed that the two cultivars differed in Cd uptake, but not in Cd translocation from roots to shoots. A homolog of OsNramp5 (natural resistance-associated macrophage protein 5), NtNramp5, was isolated from both cultivars. There was no significant difference in the expression level of NtNramp5 in the roots between the two cultivars. Sequence analysis revealed that the low Cd/Mn-accumulating cultivar possesses an NtNramp5 allele with a predicted mutation for early translation termination, resulting in a truncated protein missing 104 amino acids in the C-terminus of the full-length NtNramp5 found in the high Cd/Mn-accumulating cultivar. Both proteins were found to be localized to the plasma membrane. Heterologous expression of the two alleles of NtNramp5 in yeast showed that the full-length protein had transport activities for both Mn and Cd, whereas the truncated protein had no transport activity for Mn and a weak transport activity for Cd. These results suggest that NtNramp5 is a transporter for Mn and Cd, and the allelic variation in the coding region of NtNramp5 probaby explains the cultivar difference in Cd and Mn accumulation.

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This study determined the resistance to five different insecticides, and assessed the change in enzymes in three Myzus persicae populations in Liuyang, Guiyang, and Longshan tobacco (Nicotiana tabacum L.)-growing areas in Hunan province, China.The activities of the detoxification, protective, and digestive enzymes were determined using biochemical analysis. Results indicated that the Liuyang population had high resistance to Imidacloprid, and moderate resistance to Aacetamiprid and Cyhalothrin. The Longshan population showed low resistance to Phoxim, while the Liuyang and Guiyang populations both exhibited reduced susceptibility. All three populations exhibited reduced susceptibility to Methomyl. Field populations exhibited higher activity of detoxification enzymes [acetylcholinesterase (AchE), carboxylesterase (CarE), glutathione-S-transferase (GST), and mixed-function oxidase (MFO)], protective enzymes (superoxide dismutase [SOD], catalase [CAT], and peroxidase [POD]), and digestive enzymes (amylase [AMS]) than the susceptible population. The Liuyang population showed the highest detoxification, protective, and digestive enzyme activity of all aphid populations. The AchE activity and resistance level to acetamiprid was significantly, positively correlated. The CarE, CAT, and AMS activity and resistance to Imidacloprid were also significantly, positively correlated. The correlation between enzyme activity and resistance to methomyl was negative, except for AchE. When CarE, CAT, and AMS activity was up to 60, aphids exhibited low resistance to Imidacloprid, and when AchE activity was up to 90, aphids exhibited medium resistance to Imidacloprid. These results provide the theoretical basis for predicting regional resistance of M. persicae to Imidacloprid and Acetamiprid, which can be used to delay evolution of resistance of M. persicae to insecticides in the field.

In this study, the effects of Ligusticum chuanxiong extract as herbicide safeners were determined on glutathione-S-transferase (GST) activity of rice crop. Two main extract compounds, Z-ligustilide and senkyunolide A, were identified by high performance liquid chromatography and liquid chromatography-mass spectrometry. In both bioassays conducted in agar and soil, the whole L. chuanxiong extract, as well as two active components individually were effective in safening the growth of rice seedlings against S-metolachlor toxicity. Z-Ligustilide was a better safener than senkyunolide A, and both compounds were more protective of shoots than roots. After herbicide-inhibited rice seedlings were treated with Z-ligustilide, GST activity significantly increased, suggesting the safening effect of this L. chuanxiong extract component involves GST.

The study was aimed at exploring the effects of applying ordinary and nano zeolite on the soil pH, soil available cadmium (Cd) content, soil Cd speciation and Cd uptakes by tobacco using pot experiment with simulated Cd contaminated soil indoors. The results showed that soil pH increased and available Cd content reduced with the amount of ordinary and nano zeolite increasing. Compared with the control, the application of ordinary and nano zeolite increased soil pH at 0.47 - 1.05 and 0.73 - 1.57, respectively, and reduced the available Cd contents at 19.3% - 32.7% and 23.2% - 40.5%, respectively. In addition, soil pH had significantly negative correlation with available Cd content in each treatment (p<0.05). Nano zeolite could more effectively reduce Cd contents of all parts of tobacco than ordinary zeolite with the same amount treatments, and Cd content in all parts of tobacco plants was positively correlated with soil available Cd content. The content of exchangeable Cd (EXE) in soil decreased to some extent with different zeolite treatments, application of nano zeolite was better than that of application of ordinary zeolite in reducing Cd bioavailability and transferability. Overall, application of nano zeolite has an advantage over ordinary zeolite in reducing available Cd content in soil and Cd content in tobacco.