Elucidating the Adverse Outcome Pathway for Grain-Quality Deterioration Induced by Brominated Flame Retardants in...

Brominated flame retardants (BFRs) pose a growing threat to agricultural safety, yet their dynamic transfer mechanisms and interference with crop metabolism remain poorly understood. This study systematically unravels the lifecycle translocation of BFRs in rice and deciphers the signaling-mediated cascade leading to grain-quality deterioration. BFR accumulation did not follow a simple xylem-mediated transport pattern; instead, secondary enrichment occurred during grain filling, inversely correlated with their logK_ow and molecular weight. In particular, the concentration of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) in the panicles increased sharply from ∼1 ng/g at the heading stage to 16.5 ng/g at the filling stage, reaching 42.0 ng/g at maturity, representing an order-of-magnitude increase. This accumulation critically coincided with a marked depletion of nutritional components: amylopectin and total protein decreased by 10.3-17.7%, accompanied by a 12.5% reduction in 1000-grain weight. Through integrated transcriptomic, proteomic, and metabolomic analyses, along with a novel motif-based unbiased screening method, we deciphered the core adverse outcome pathway (AOP). BFRs advanced the abscisic acid (ABA) peak by 5 days and increasing its concentration ∼20% compared to the control. This intensified ABA signaling pathway upregulated tricarboxylic acid cycle enzymes by 2-5-fold, and redirected carbon flux from starch synthesis toward energy production. This metabolic shift accelerates the cotransport of selected BFRs (e.g., BDE-47) into the developing grain, driving premature maturation and nutritional loss. By establishing a complete "signal activation → metabolic reprogramming → pollutant co-transport → quality deterioration" AOP framework, this study provides a mechanistic foundation for understanding the potential dietary implications of BFRs in rice, offering crucial insights for safeguarding food safety and controlling agricultural contamination.