Nickel oxide nanoparticles (NiO-NPs) alleviate cadmium (Cd) stress in tomato by activating the expression of SlERF4 and SlWRI1

Soil cadmium pollution is becoming an increasingly acute environmental problem for both plants and humans. Although several nanoparticles seemingly play a significant role in tolerance to cadmium toxicity, the role of nickel oxide nanoparticles (NiO-NP) in cadmium tolerance remains unclear. In this study, we showed that pre-treatment with NiO-NPs enhanced tomato tolerance to cadmium stress and reduced its toxic effects. Our findings showed that NiO-NP treatment promoted tomato seedling growth by enhancing root and shoot nutrient accumulation and increasing chlorophyll content. Concomitantly, NiO-NP treatment significantly reduced root and shoot cadmium contents, leading to a significant reduction in cadmium phytotoxicity. Furthermore, NiO-NP treatment increased the activities of antioxidant enzymes and reduced malondialdehyde and reactive oxygen species contents in roots and leaves of seedlings growing under cadmium stress. Mechanistic investigations revealed that NiO-NP treatment regulated the expression of stress-responsive genes, including transcription factors SlERF4 and SlWRI1. Consistently, overexpression of SlERF4 and SlWRI1 in yeast cells resulted in cadmium stress tolerance. Notably, cadmium content in overexpressing cells was reduced by 39.10 % and 81.21 % for SlERF4 and SlWRI1, respectively, compared to the wild-type. These results suggest that NiO-NPs enhanced cadmium stress tolerance by activating SlERF4 and SlWRI1 , thereby promoting tomato seedling growth. Our study opens a new avenue for gene identification and genetic modification to develop cadmium-tolerant crops, thereby ensuring vegetable production and food security. Additionally, it has significant implications for the development of novel strategies to mitigate the adverse effects of cadmium pollution on agricultural productivity. • Cadmium (Cd) toxicity inhibits the growth of tomato seedlings. • The pre-application of NiO-NP effectively regulates the plant defense system under Cd stress. • NiO-NP modulate the hormonal signaling pathways in plants, enhancing tolerance to cadmium stress. • The transcription factors SlERF4 and SlWRI1 promote cadmium stress tolerance in yeast.