Silicon alleviates long-term copper toxicity and influences gene expression in Nicotiana tabacum

Abstract

Silicon (Si) is beneficial for plant growth and aids in stress tolerance. In this study, the effects of Si on long-term copper (Cu) toxicity in the low Si accumulator Nicotiana tabacum were evaluated. Silicon supplementation alleviated growth inhibition in roots and shoots of N. tabacum exposed to Cu toxicity. Alleviation of Cu toxicity correlated with increased Si accumulation in roots and leaves, suggesting N. tabacum contains a stress-regulated mechanism for Si transport. Root Cu concentration decreased in Si-supplemented plants exposed to Cu toxicity. Interestingly, Copper Transporter 1 (COPT1) expression decreased in roots of Si-supplemented plants exposed to Cu toxicity, which may contribute to Cu uptake reduction. Decreases in ethylene (ET) biosynthetic gene expression were previously implicated in Si-mediated stress alleviation. In the present study, Si-mediated alleviation of Cu toxicity corresponded with increased ET biosynthetic gene expression.

Keywords:

• copper
• ethylene
• metal toxicity
• polyamine
• silicon
• tobacco

Acknowledgments

The authors thank Lirim Shemshedini and Wendy Zellner, both in the Department of Biological Sciences at the University of Toledo, for critical comments on the manuscript. The authors also thank Douglas Sturtz of the USDA-ARS for his assistance with ICP-OES, and the University of Toledo Plant Science Research Center.

Additional information

Funding

This work was supported by USDA-ARS Specific Cooperative Agreement: 58-5082-6-012.