An ICT-based ratiometric fluorescent probe for tracking and imaging SO2 during Cd-induced stress in plants

Cadmium (Cd) is a common and highly toxic heavy metal that poses a significant threat to plant growth and development, as well as human and animal health through the food chain. In contrast, sulfur dioxide (SO2) and its derivatives, which are major air pollutants, can also have beneficial effects on plant resistance and seed germination at low concentrations. However, the role of SO2 in the process of plant response to stress and adversity remain poorly understood. Herein, we have developed an ICT-based and D-π-A structure ratiometric fluorescent probe, TPE-BA, with the photoluminescence properties of AIE. This probe exhibited high sensitivity and excellent selectivity for detecting SO2 in living plants. Probe TPE-BA showed a fast response time and has been used to detect exogenous changes in SO2 levels in plants by fluorescence imaging. In addition, the process of Cys metabolism produces endogenous SO2 were confirmed in the roots of tobacco seedlings. The results suggested that there is an imbalance of oxidative stress levels and an upregulation of SO2 levels during the response of tobacco seedlings to Cd-induced stress, indicating that SO2 plays a crucial role as a signaling molecule in plant response to stress.