Accumulation and metabolism of pyroxasulfone in tomato seedlings

Pyroxasulfone (PYS) is an isoxazole herbicide favored for its high activity. However, the metabolic mechanism of PYS in tomato plants and the response mechanism of tomato to PYS are still lacking. In this study, it was found that tomato seedlings had a strong ability to absorb and translocate PYS from roots to shoots. The highest accumulation of PYS was in the apex tissue of the tomato shoots. Using UPLC-MS/MS, five metabolites of PYS were detected and identified in tomato plants, and their relative contents in different parts of tomato plants varied greatly. The serine conjugate, DMIT [5, 5-dimethyl-4, 5-dihydroisoxazole-3-thiol (DMIT)] &Ser, was the most abundant metabolites of PYS in tomato plants. In tomato plants, the conjugation of thiol-containing metabolic intermediates of PYS to serine may mimic the cystathionine β-synthase-catalyzed condensation of serine and homocysteine (in the pathway sly00260 sourced from KEGG database). This study ground breakingly proposed that serine may play an important role in plant metabolism of PYS and fluensulfone (whose molecular structure is similar to PYS). PYS and atrazine (whose toxicity profile is similar to PYS but not conjugate with serine) produced different regulatory outcomes for endogenous compounds in the pathway sly00260. Differential metabolites in tomato leaves exposed to PYS compared with the control, including amino acids, phosphates, and flavonoids, may play important roles in tomato response to PYS stress. This study provides inspiration for the biotransformation of sulfonyl-containing pesticides, antibiotics and other compounds in plants.