Expression of a Brassica napus metal transport protein (BnMTP3) in Arabidopsis thaliana confers tolerance to Zn and Mn.

The essential micronutrient elements zinc (Zn) and manganese (Mn) are crucial for plant growth and development. As an important oil crop, the yield and quality of rapeseed are affected by Zn and Mn toxicity. The cation diffusion facilitator (CDF) family of proteins play significant roles in maintaining intracellular ionic homeostasis and tolerance in plants. However, research on CDF proteins in rapeseed is lacking. In this study, the function of a Brassica napus cation diffusion facilitator/ metal tolerance protein (CDF/MTP) was investigated. The protein, abbreviated BnMTP3 is homologous to the Arabidopsis thaliana MTP3 (AtMTP3). Heterologous expression of BnMTP3 in yeast enhanced tolerance and intracellular sequestration of Zn and Mn. Expression of BnMTP3 in A. thaliana increased Zn and Mn tolerance and markedly increased Zn accumulation in roots. Quantitative RT-PCR analysis showed that BnMTP3 is primarily expressed in roots, and subcellular localization suggested that BnMTP3 is localized in the trans-Golgi network (TGN) and the prevacuolar compartment (PVC) in Arabidopsis and rape protoplast. After treatment with Zn and Mn, BnMTP3 was observed on the vacuolar membrane in transgenic Arabidopsis lines. These findings suggest that BnMTP3 confers Zn and Mn tolerance by sequestering Zn and/or Mn into the vacuole.