Auxin-Regulated PAHs Absorption in Wheat Roots: Insights from Kinetics, Enzymatic Activity, and Transcriptomic Profiling

Auxins are key regulators of plant development, but their role in the uptake of polycyclic aromatic hydrocarbons (PAHs) remains largely unexplored. Here, we revealed the regulatory effects of exogenous auxin and antagonists on PAHs absorption by wheat roots. The optimum regulatory concentrations for indole-3-acetic acid (IAA), 2-(4-chlorophenoxy)-2-methylpropionic acid (PCIB), and β-naphthylacetic acid (2-NAA) are 100 μmol L^-1, while α-naphthaleneacetic acid (1-NAA) is 10 μmol L^-1. The uptake kinetics of PAHs follow the Elovich model over time and the Michaelis-Menten model across concentrations. IAA and 1-NAA markedly upregulate <i>TaHA1</i> expression and activate plasma membrane H⁺-ATPase, facilitating H⁺-coupled PAHs uptake. Transcriptome analysis further showed that auxin cotreatment significantly enriched plant hormone signal transduction and ABC transporter pathways, with regulation of <i>SAUR</i> and <i>ABC</i> family genes, suggesting a coordinated regulatory mechanism. These findings offer insights into auxin-regulated PAHs transport in wheat roots and provide a theoretical basis for phytoremediation and food safety improvement.