Metal tolerance protein CsMTP4 has dual functions in maintaining zinc homeostasis in tea plant

Plants have evolved a series of zinc (Zn) homeostasis mechanisms to cope with the fluctuating Zn in the environment. How Zn is taken up, translocated and tolerate by tea plant remains unknown. In this study, on the basis of RNA-Sequencing, we isolated a plasma membrane-localized Metal Tolerance Protein (MTP) family member CsMTP4 from Zn-deficient tea plant roots and investigated its role in regulation of Zn homeostasis in tea plant. Heterologous expression of CsMTP4 specifically enhanced the tolerance of transgenic yeast to Zn excess. Moreover, overexpression of CsMTP4 in tea plant hairy roots stimulated Zn uptake under Zn deficiency. In addition, CsMTP4 promoted the growth of transgenic Arabidopsis plants by translocating Zn from roots to shoots under Zn deficiency and conferred the tolerance to Zn excess by enhancing the efflux of Zn from root cells. Transcriptome analysis of the CsMTP4 transgenic Arabidopsis found that the expression of Zn metabolism-related genes were differentially regulated compared with wild-type plants when exposed to Zn deficiency and excess conditions. This study provides a mechanistic understanding of Zn uptake and translocation in plants and a new strategy to improve phytoremediation efficiency.