γ-Aminobutyric Acid Alleviates Programmed Cell Death in Two Brassica Species Under Cadmium Stress

Previous studies have demonstrated that γ-Aminobutyric acid (GABA) effectively alleviates heavy metal stresses by maintaining the redox balance and reducing the accumulation of reactive oxygen species (ROS). However, little is known about the role of GABA on programmed cell death (PCD) under Cd treatments in plants. The present study investigated the effects of GABA on Cd-induced PCD in two <i>Brassica</i> species, oilseed rape (<i>Brassica napus</i>, <i>Bn</i>), and black mustard (<i>Brassica juncea</i>, <i>Bj</i>). We observed that GABA significantly alleviated Cd-induced PCD by enhancing antioxidant systems, inhibiting chromatin condensation in the nucleus, and reducing DNA fragmentation under Cd stress. Moreover, GABA may not only reduce caspase-3-like activity by repressing gene expression, but also regulate transcription of PCD-related genes. <i>Bn</i> showed lower Cd accumulation and lower tolerance, with more pronounced PCD, compared with <i>Bj</i>. Our results provide new insights into the mechanism that GABA enhances Cd tolerance in plants.