Exogenous γ‐aminobutyric acid alleviates cadmium stress in <i>Camptotheca acuminata</i> by reducing cadmium accumulation

Abstract Cadmium (Cd) is a toxic heavy metal that severely disrupts plant growth and cellular homeostasis. γ‐aminobutyric acid (GABA) has shown potential in alleviating Cd toxicity to Camptotheca acuminata , but its effects on the molecular responses remain unclear. In this study, the effects of exogenous GABA on the Cd tolerance and its molecular mechanisms in C. acuminata were investigated. Cd treatment reduced the root and shoot biomass and induced the Cd accumulation, which was primarily confined to roots, resulting in a low Cd translocation factor. GABA application partially alleviated the biomass reduction and decreased the Cd accumulation. Transcriptome sequencing further revealed 336 differentially expressed genes (DEGs) under Cd stress compared with control, whereas only 68 DEGs were detected following GABA treatment. GO and KEGG enrichment analyses revealed that Cd treatment disrupted metabolic, cellular, and molecular processes, including the oxidative stress response, cell wall metabolism, and hormone signaling. GABA treatment modulated the Cd‐induced DEGs, particularly those involved in the calcium signaling, MAPK pathway, and antioxidant defense system, restoring the transcriptional balance and enhancing the stress response pathways. RT‐qPCR confirmed the regulatory effects of GABA on key genes, including the calcium signaling–related genes KRP1 and CML46 , which were upregulated under Cd treatment but suppressed by GABA, as well as the growth‐related genes BRR1 and BT1 , which were upregulated by GABA. Therefore, GABA plays a critical role in enhancing C. acuminata tolerance to Cd stress, offering new insights into its mechanisms and potential application for mitigating heavy metal toxicity in plants.