Exogenous γ-aminobutyric acid alleviates the cadmium toxicity in rice ( Oryza sativa L.) by promoting growth, regulating Cd distribution, and modulating stress-responsive gene expression

Cadmium (Cd) is a highly toxic heavy metal that poses a serious threat to rice (Oryza sativa L.) productivity and food safety. γ-aminobutyric acid (GABA) is known to promote rice growth and reduce Cd uptake, but mechanism of its role in alleviating Cd toxicity in rice remains unclear. In this study, we examined the effects of GABA (0.25 mmol L−1) on biomass accumulation, Cd distribution, and gene expression in rice under Cd stress (1 mg L−1) with three biological replicates. GABA application increased root and shoot biomass of rice (Duncan’s multiple range test) while reducing Cd content in both tissues (Student’s t-test). Compared with Cd treatment, GABA increased root and shoot biomass by 47.22% and 23.72%, respectively, and decreased root and shoot Cd contents by 6.56% and 39.16%, respectively. GABA also altered Cd partitioning by promoting its redistribution to soluble and organelle/membrane fractions in roots and shoots. Transcriptome profiling revealed differentially expressed genes (DEGs, fold-change thresholds ≥ 1.5 and false discovery rate < 0.05) involved in photosynthesis, glutathione metabolism, and light-responsive pathways under Cd stress. A total of 1570, 1233, and 232 DEGs were identified in control vs Cd treatment, control vs GABA treatment, and Cd treatment vs GABA treatment, respectively. GABA modulated DEGs associated with the stress response, ion transport, and secondary metabolism. RT-qPCR validation of four key DEGs, ferritin 1 (Fer1), glutathione S-transferase 6 (GSTU6), cytochrome P450 709B2-like (CYP709B2), and ent-sandaracoparadiene 3-hydroxylase-like (CYP701A8), confirmed the transcriptomic trends. These findings suggest that GABA alleviates Cd toxicity in rice by promoting growth, regulating Cd distribution, and modulating stress-responsive gene expression, offering new insights into GABA-mediated heavy metal tolerance.