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Abstract <p>Previous studies on cadmium (Cd) accumulation in <i>Salvia miltiorrhiza</i> Bge. have identified significant ecotypic differences: the Sichuan ecotype (SC) exhibits low Cd accumulation, whereas the Shandong ecotype (SD) shows high Cd accumulation. We further identified the NRAMP transporter SmNRAMP5 as a key candidate gene responsible for these phenotypic differences. To elucidate the mechanism underlying differential Cd transport, we cloned and compared <i>SmNRAMP5</i> alleles from the SC and SD ecotypes. Functional characterization in yeast confirmed that the SD allele possesses a higher Cd transport capacity than the SC allele. We then used site-directed mutagenesis to demonstrate that replacing the key residues Isoleucine 397 and Methionine 529 in the SD allele with the corresponding residues (Threonine and Alanine) found in the SC allele significantly reduced cadmium uptake. In conclusion, this study establishes SmNRAMP5 as the major transporter mediating Cd hyperaccumulation in <i>S. miltiorrhiza</i> and uncovers the key residues governing its transport function. These findings provide critical genetic targets and a theoretical foundation for breeding low-Cd cultivars, thereby ensuring the safer clinical use of this important medicinal herb.</p>

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Functional Divergence of SmNRAMP5 Alleles Underlies Differential Cadmium Accumulation in Salvia miltiorrhiza Ecotypes

  • 期刊论文

  • 发表日期：

    2026年7月2日

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  • S. Dai,
  • J. Liao,
  • Y. Shang,
  • Z. Zhang,
  • R. Yang,
  • Y. Jiang,
  • L. Wang,
  • X. Deng,
  • Y. Zhang,
  • L. Lin,
  • L. Zhang

摘要

Abstract

Previous studies on cadmium (Cd) accumulation in Salvia miltiorrhiza Bge. have identified significant ecotypic differences: the Sichuan ecotype (SC) exhibits low Cd accumulation, whereas the Shandong ecotype (SD) shows high Cd accumulation. We further identified the NRAMP transporter SmNRAMP5 as a key candidate gene responsible for these phenotypic differences. To elucidate the mechanism underlying differential Cd transport, we cloned and compared SmNRAMP5 alleles from the SC and SD ecotypes. Functional characterization in yeast confirmed that the SD allele possesses a higher Cd transport capacity than the SC allele. We then used site-directed mutagenesis to demonstrate that replacing the key residues Isoleucine 397 and Methionine 529 in the SD allele with the corresponding residues (Threonine and Alanine) found in the SC allele significantly reduced cadmium uptake. In conclusion, this study establishes SmNRAMP5 as the major transporter mediating Cd hyperaccumulation in S. miltiorrhiza and uncovers the key residues governing its transport function. These findings provide critical genetic targets and a theoretical foundation for breeding low-Cd cultivars, thereby ensuring the safer clinical use of this important medicinal herb.