An Interplay Between Gama-Aminobutyric Acid and Hydrogen Sulfide and Their Potential Role in Mitigating Cadmium Toxicity in Rice Seedlings.

Both hydrogen sulfide (H2S) and gamma-aminobutyric acid (GABA) are known to regulate antioxidative metabolic pathways for developing stress resilience in plants. However, it is unknown whether they work together or exhibit independent signaling in maintaining ROS homeostasis during cadmium (Cd) stress. Therefore, this study was undertaken to investigate the potential implications of GABA and H2S signaling in regulating Cd stress in rice seedlings. The results show that the exposure to Cd stress affects photosynthesis and nitrogen assimilation, increases ROS accumulation, weakens the antioxidant system, and disturbs thiol metabolism in rice seedlings. Cd stress also stimulated aerenchyma formation, which was further enhanced by GABA application, while H2S did not exhibit any significant effect. GABA treatment also decreased the Cd-induced tannin deposition in roots. Moreover, exogenous GABA and H2S application also enhanced plant growth and chlorophyll content, and restored photosynthesis and nitrogen homeostasis by stabilizing NR, NiR, and GS/GOGAT activities under Cd stress. Further, thiol metabolism was also strengthened, aiding in redox balance restoration under Cd stress. GABA was more effective than H2S in mitigating Cd stress. Moreover, both GABA and H2S were capable of mitigating Cd stress, and our results revealed that GABA seems to be a downstream component of H2S signaling. The results of this study highlight a hopeful and sustainable approach for refining crop resilience to heavy metal stress and Cd stress in particular.