The MATE family transporter CaDTX12 confers cadmium accumulation in pepper (Capsicum annuum L.)

Cadmium (Cd) contamination in agricultural soils poses a significant threat to the safety of pepper (Capsicum annuum L.) products. The development of low-Cd-accumulating pepper varieties is a promising strategy to ensure food safety. To identify potential genetic targets involved in regulating Cd accumulation in pepper fruits, we conducted a genome-wide selective sweep analysis in high- and low-Cd-accumulating pepper materials. By integrating genome-wide selective sweep analysis with gene expression profiling, we identified CaDTX12 (Capana11g002353), a gene encoding a detoxification efflux carrier (DTX). Heterologous expression of CaDTX12 significantly enhanced Cd accumulation in both yeast and Arabidopsis. Silencing of CaDTX12 via VIGS resulted in a 27.8% reduction in Cd content in pepper fruits. Two genotypic variants of CaDTX12 were identified (X15-CaDTX12 and X55-CaDTX12). Among these, X15-CaDTX12 represents the functional allele, exhibiting significantly higher Cd accumulation capacity compared with X55-CaDTX12. The CaDTX12 protein is localized to the tonoplast membrane. Furthermore, CaDTX12 exhibited a consistent expression pattern with that of CaDTX1, CaHMA1, CaHMA3, CaNRAMP3, CaZIP11, and CaSOD-Fe, and the silencing of CaDTX12 led to the downregulation of these associated genes. In conclusion, our findings suggest that CaDTX12 functions in Cd transport on the vacuolar membrane, and together with proteins including CaDTX1, CaHMA1, CaHMA3, CaNRAMP3, CaZIP11, and CaSOD-Fe, it collectively promotes Cd accumulation in pepper fruits and enhances Cd tolerance. These findings provide novel insights into the molecular mechanisms underlying Cd accumulation in pepper fruits and offer potential genetic targets for developing low-Cd-accumulating pepper varieties through breeding programs.