Ecological Impacts of Integrated Irrigation-Aquaculture on Rice Seedlings: Lysine-Enhanced Florfenicol Uptake and Its Transcription Interference

Integrated irrigation-aquaculture (IIA) systems recycle aquaculture wastewater for crop irrigation, yet the ecological risks of fishery drugs under protein-rich dissolved organic matter (DOM) remain unclear. To evaluate crop responses, rice seedlings were exposed to florfenicol (FF) with lysine, simulating high-protein DOM matrix effects. A clear dose-response relationship was observed for FF exposure, with an EC₁₀ of 1.58 mg·L^-1. At 1/4 EC₁₀, FF promoted growth while inducing oxidative stress, glutathione S-transferase activation, and lignin synthesis. At EC₁₀, FF suppressed root development by down-regulating sulfur and ethylene pathways, disrupting antioxidant balance, and triggering defensive lignification that constrained growth. Notably, lysine did not merely coexist with FF but significantly enhanced its uptake and translocation, thus enhancing the oxidative stress and transcriptional response caused by FF. Molecular interaction analysis indicated that lysine facilitated FF absorption through hydrogen bonding, halogen bonding, and hydrophobic interactions with lysine-histidine transporters, lowering the binding energy and increasing FF bioaccumulation. Although lysine upregulated amino acid metabolism pathways, this partial metabolic adjustment was insufficient to offset the increased internal FF burden. This study delves into the molecular mechanisms underlying rice ecological disorders in the IIA system, providing a scientific basis for agricultural water management.