The Transcription Factor AtANAC070 Enhances Zinc Tolerance by Promoting AtMTP1 Expression in Arabidopsis Thaliana

The NAC transcription factor AtANAC070 functions in zinc tolerance by directly activating AtMTP1 transcription to promote vacuolar zinc sequestration and homeostasis in A. thaliana. Zinc (Zn) is an essential micronutrient for plant growth, but it becomes toxic when present in excess. An initial screen of Arabidopsis thaliana T-DNA insertion mutants suggested a positive role of AtANAC070 in tolerance to excess Zn. AtANAC070 expression was induced under excess Zn, and loss of function of AtANAC070 led to increased Zn sensitivity and higher Zn accumulation. Conversely, AtANAC070 overexpression enhanced Zn tolerance and reduced Zn accumulation. Yeast one-hybrid assays identified Metal Tolerance Protein 1 (AtMTP1), which encodes a key transporter mediating vacuolar sequestration of excess Zn, as a downstream target of AtANAC070. Dual-luciferase reporter and real-time quantitative PCR (RT-qPCR) assays confirmed that AtANAC070 directly binds to the AtMTP1 promoter to activate its expression. The atmtp1 mutant accumulated more Zn than the WT and was more sensitive to excess Zn, whereas AtMTP1-overexpressing lines showed the opposite phenotype. The atanac070 atmtp1 double mutant displayed Zn sensitivity comparable to that of atmtp1 mutant, while AtMTP1 overexpression in the atanac070 background reduced Zn accumulation and restored Zn tolerance. These results indicate that AtANAC070 contributes to Zn homeostasis under excess Zn by promoting AtMTP1 expression.