Antibiotic-induced photosynthetic dysfunction in wheat: Coupled inhibition of light reactions and carbon assimilation...

Antibiotics, as emerging environmental contaminants, pose potential risks to crop photosynthesis and productivity. This study systematically investigated the phytotoxic effects of enrofloxacin (ENR), levofloxacin (LVX), and roxithromycin (ROX) on wheat (Triticum aestivum L.) seedlings. Exposure to ENR and LVX led to significant reductions in photosynthetic pigment content, chlorophyll synthesis precursors, and net photosynthetic rate, accompanied by severe chloroplast ultrastructural damage, thylakoid disintegration, and mitochondrial cristae impairment. Chlorophyll fluorescence parameters indicated PSII dysfunction and impaired electron transport under ENR and LVX stress. In contrast, ROX treatment increased pigment content, maintained chloroplast integrity, and increased chloroplast numbers. All three antibiotics stimulated key carbon assimilation enzymes including Rubisco, PEPC, NADP-ME, and PPDK. Transcriptomic analysis revealed downregulation of photosynthesis-related genes (e.g., PsbA, PsaA, PetA, PetD) and F-type ATPase subunits under ENR and LVX, whereas genes involved in redox maintenance (PetH) were upregulated. Metabolomic profiling showed accumulation of oxalic acid, methylamine, and palmitic acid under ENR and LVX, indicating membrane damage, protein degradation, and may disrupt energy metabolism. Significant alterations in fatty acid biosynthesis, pyrimidine metabolism, and GPI anchor biosynthesis pathways further confirmed antibiotic-induced metabolic reprogramming. This study provides new insights into the differential impacts of antibiotics on crop photosynthesis and cellular integrity, emphasizing the need for ecological risk assessment of antibiotic contamination in agricultural systems.