Objective Cadmium (Cd) is a toxic heavy metal pollutant widely present in the environment. Even at low concentrations, it can harm plant growth and development. Plants have evolved various defense mechanisms against heavy metal stress. Neolamarckia cadamba is a fast-growing tree species with broad application prospects and potential for phytoremediation; however, the molecular regulatory mechanisms underlying its response to cadmium stress remain unclear, limiting its application in the remediation of heavy metal-contaminated soils. Therefore, this study aimed to screen and identify key cadmium-stress-responsive transporter genes in Neolamarckia cadamba, elucidate their functions, clarify the mechanisms of cadmium tolerance, and provide a theoretical basis for its application in phytoremediation.

Method Based on the Neolamarckia cadamba genomics data, bioinformatics methods were employed to identify the heavy metal-transporting ATPase (HMA) gene family in Neolamarckia cadamba. Transcriptome data were analyzed to examine the expression patterns of NcHMA genes across different tissues and under abiotic stresses, with RT-qPCR validation of their expression profiles under cadmium stress.

Result The NcHMA gene family comprises nine members (NcHMA1-NcHMA9), classified into two groups representing divalent Zn/Co/Cd/Pb-ATPases (Groups I and II) and monovalent Cu/Ag-ATPases (Groups III-V). Genes within the same evolutionary branch exhibit similar conserved motif patterns and intron-exon structures. Analysis of promoter cis-acting elements revealed that NcHMA gene expression is regulated by multiple factors including light response, plant hormone response, abiotic stress response, plant development, and metabolism. Transcriptome data and RT-qPCR results revealed that NcHMA family genes were primarily expressed in roots. NcHMA2 (evm.model.Contig39.142.1), NcHMA5 (evm.model.Contig264.111), and NcHMA1 (evm.model.Contig5.132) exhibited a downward trend in expression levels. In contrast, NcHMA8 (evm.model.Contig264.110), NcHMA7 (evm.model.Contig541.7), and NcHMA4 (evm.model.Contig396.34) showed a slight upregulation in the early stage, followed by a significant increase in the late stage. Yeast heterologous expression experiments demonstrated that NcHMA2 (evm.model.Contig39.142.1) possesses cadmium transport function.

Conclusion The NcHMA2 (evm.model.Contig39.142.1) gene in the Neolamarckia cadamba was significantly induced under cadmium stress, indicating its potential involvement in regulating the plant’s response to cadmium stress. This result provides direct evidence for the subsequent in-depth analysis of its cadmium resistance function.