Cadmium Stress Response of ABC Transporters in Ligusticum chuanxiong: Genome-Wide Identification and Bioinformatic Characterization

Background: Ligusticum chuanxiong Hort. is a well-known traditional Chinese medicinal herb whose clinical application and international trade had been constrained by cadmium (Cd) contamination. However, the molecular mechanisms underlying its response to cadmium stress remained poorly understood. The ATP-binding cassette (ABC) transporter family plays crucial roles in various plant processes, including growth and development, hormone transduction, and stress responses. This study aimed to analyze the ABC transporter genes in L. chuanxiong to better understand their roles during cadmium stress responses. Methods: Genome-wide identification of ABC genes in L. chuanxiong was performed, and transcriptome sequencing of rhizomes under cadmium stress was conducted. Differentially expressed LcABC genes were screened using bioinformatic analysis. Results: A total of 368 LcABC genes were identified. Transcriptome analysis revealed 37 upregulated LcABC genes, which were classified into six subfamilies. Cis-element analysis indicated that their promoters contain hormone-, growth-, and stress-responsive elements. Notably, LcABCG8, LcABCG48, and LcABCG108 contain stress-responsive elements and show close evolutionary relationships with heavy metal-responsive genes such as AtABCC1/2/3 and AtABCG36/40, suggesting that they could be key candidates. qRT-PCR validation of nine LcABC genes confirmed their differential sensitivity to cadmium stress. Conclusions: This study conducted a comprehensive identification of the ABC gene family in L. chuanxiong. By integrating transcriptomic data with systematic bioinformatic analyses, we identified several LcABC transporters that may play important roles in cadmium stress responses. The results provide insights into the molecular mechanisms of ABC transporters in cadmium stress responses in L. chuanxiong and offer strategies for reducing cadmium accumulation.