Brassinosteroid Signaling and Its Protective Role Against Heavy Metal-Induced Phytotoxicity

Аннотация

Rapid industrialization and urbanization have led to the widespread presence of heavy metals (HMs) in the environment. The environment is disrupted by the assimilation of these metals into the food chain. Elevated concentrations of HMs in the environment disrupt the normal functioning of diverse physiological and biochemical systems in plants. Plant growth regulators have effectively counteracted the detrimental impact of metal exposure on plant growth. Brassinosteroids (BRs) are a novel plant hormone that exhibit substantial growth-promoting effects. BRs have the ability to enhance plant responses to abiotic stressors, including HMs toxicity. BR application positively regulates seedling growth and development, proline accumulation, protects the photosynthetic system, upregulates secondary metabolite production, maintains redox homeostasis, and balances mineral homeostasis. Importantly, BRs effectively decreased the metal accumulation and enhanced mineral nutrient accumulation from root to shoot. Plants exposed to HMs and treated with BRs activate their antioxidant defense system and decrease the concentration of toxic elements. This may be attributed to the capacity of BRs to enhance cell membrane permeability and interact with membrane-bound proteins. This review systematically summarizes the core mechanisms underlying BR-mediated mitigation of HM stress. Specifically, we highlight three principal mechanisms: the activation of the antioxidant defense system to scavenge reactive oxygen species (ROS) and maintain redox homeostasis; the regulation of metal transport and partitioning, restricting HM accumulation in sensitive tissues while promoting essential nutrient uptake; and the protection of photosynthetic machinery and ultrastructure. Furthermore, we discuss the crosstalk between BR signaling and other hormonal pathways. This review aims to provide a theoretical basis for the application of BRs in remediation strategies for HM-contaminated soils.