Toxicity and Glutathione <i>S</i>-Transferase-Catalyzed Metabolism of <i>R</i>-/<i>S</i>-Metolachlor in Rice
J.-T. Wei, Jinyi Chen, Zhanzhan Zhang, Yaxin Ban, Jiaying Guo, Liyao Dong, Zhike Feng
Abstract
Metolachlor, the chiral herbicide, inhibits the very-long-chain fatty acid (VLCFA) synthesis; elucidating the enantioselectivity between R - and S -metolachlor in the toxicological difference will facilitate the understanding of the site of action. We found that the endogenous accumulation of C22 VLCFAs decreased in both R -/ S -metolachlor -treated plants by 6, 12, and 24 h after treatment, with more significant reduction in the S isomer group. Gene expression of glutathione S -transferase OsGST Tau members were obviously induced upon treatments with S or R isomer; both OsGSTU1 and OsGSTU4 can metabolize metolachlor effectively, with S isomer as the preference by directly catalyzing the conjugation between S -metolachlor and glutathione. In the current study, we provide the first evidence in rice seedlings that S -metolachlor showed herbicidal toxicity by blocking the synthesis of C22-type fatty acid, which eventually affects the whole elongation chain of (V)LCFA. Meanwhile, OsGSTU1 and 4 metabolize the metolachlor with the S isomer as preference. All of these discoveries broaden our knowledge about metolachlor toxicology and enantioselectivity.