Cadmium stress triggers dopamine signaling in duckweed (

INTRODUCTION: Cadmium (Cd) contamination poses a serious threat to aquatic ecosystems and human health. Duckweed has been recognized as a promising plant for phytoremediation of heavy metal-polluted water, yet the signaling mechanisms underlying its response to Cd stress remain poorly understood. Dopamine (DA), a catecholamine known as a neurotransmitter in animals, has recently been identified as a potential regulatory molecule in plants, but its dynamic response under heavy metal stress has not been clearly characterized. METHODS: In this study, dopamine signaling dynamics in duckweed (Lemna turionifera 5511) were investigated using the genetically encoded fluorescent dopamine sensor GRAB-DA2h. Stable transgenic duckweed lines expressing the sensor were generated via Agrobacterium-mediated transformation, enabling real-time visualization of intracellular dopamine changes. RESULTS: With Cd treatment, GRAB-DA2h fluorescence in root tissues increased within 1 minute and remained elevated during the imaging period, indicating a rapid early signaling response. Following a 24-hour exposure to 50 mM CdCl2, the protoplasts isolated from fronds exhibited an increase in fluorescence intensity from 345.18 to 391.14, while those derived from roots showed an increase from 112.75 to 140.68. DISCUSSION: These findings provide direct evidence of dopamine signaling dynamics in duckweed under cadmium stress and demonstrate the applicability of genetically encoded biosensors for studying plant stress signaling. This work offers new insights into plant responses to heavy metal stress and may contribute to improving phytoremediation strategies.