The vascular preferentially expressed OsCOPT7 mediates the long-distance transport of copper in rice

Aims: Copper (Cu) is one of the essential micronutrients for plants, but extremely narrow range of satisfactory Cu is required for plant survival and productivity. Herein, we’d like to identify and functional characterize the putative transporters required to adapt to the fluctuant Cu. Methods: We investigated OsCOPT7 from evolutionary, physiological and molecular perspectives. Results: OsCOPT7 is ubiquitously expressed in rice tissues with the most abundant transcripts in the vascular cylinder of root, node and leaf. Cu translocation from roots to shoots, Cu concentrations in the xylem sap, straw and brown rice were significantly reduced in the knockout mutants (oscopt7-2 and oscopt7-3) compared to those of wild type (WT). Disruption of OsCOPT7 partially recovered the retarded seminal root elongation induced by excess Cu, while the shoot biomass was obviously decreased by Cu starvation. In addition, the grain yield of oscopt7-2 and oscopt7-3 was decreased by 62.8% and 43.1% compared to that of WT, respectively, accompanied with the dramatically depressed seed setting ratio. In addition, the sequences of COPT7 proteins are highly conserved in green plants, implicating the origination of it from Streptophyte algae, and Cu deficiency-induced expression of COPT7 homologous seemed evolutionary conserved in Arabidopsis and maize. Conclusions: OsCOPT7 was preferentially expressed in the vascular tissues of the organs and played key role in the long-distance transport from roots to above-ground organs, which is critical for the productivity and grain Cu accumulation. The upregulated expression of OsCOPT7 under Cu-deficient conditions implicated its vital role in adapt to Cu starvation in soil.