Discovery and structure-activity relationship of dimesulfazet: a novel rice paddy herbicide.

Dimesulfazet, a novel herbicide for use in paddy rice, was discovered during studies on haloalkylsulfonanilide derivatives. Our research revealed that cyclic sulfonamide derivatives exhibited herbicidal efficacy against paddy weeds prevalent in Japan, such as Schoenoplectiella juncoides (Roxb.) Lye. Furthermore, these derivatives showed efficacy against hard-to-control perennial sedges such as Eleocharis kuroguwai Ohwi. Subsequently, we converted the cyclic sulfonamide derivatives into cyclic amide derivatives, which demonstrated enhanced herbicidal activity. Among these derivatives, dimesulfazet was selected because of its exceptional efficacy against both annual and perennial sedges, while being safe for use on transplanted rice. A simple method was developed for the condensation of benzyl alcohol and cyclic amide intermediates to synthesize trifluoromethanesulfonanilide derivatives. We found that the mode of action of dimesulfazet involved the inhibition of very long-chain fatty acid biosynthesis. Dimesulfazet represents a valuable new tool for controlling S. juncoides, including biotypes resistant to acetolactate synthase inhibitors, and other perennial sedges in rice paddies. © 2024 Society of Chemical Industry.

Dimesulfazet, a novel rice paddy herbicide, is an inhibitor of very long-chain fatty acid biosynthesis.

Dimesulfazet can control annual and perennial sedges in rice paddies. Here we assessed its mode of action. We performed a phenotype assay of Arabidopsis, conducted a metabolomic analysis of Echinochloa crus-galli, and analyzed the endogenous concentration of very long-chain fatty acids (VLCFAs) in Schoenoplectiella juncoides. Dimesulfazet treatment caused curling and greening symptoms in the leaves and fiddlehead-like symptoms in the inflorescences of Arabidopsis. These symptoms were visually indistinguishable from those caused by flufenacet and benfuresate, which belong to Herbicide Resistance Action Committee (HRAC) Group 15. We performed GC-MS/MS analysis of primary metabolites and LC-MS analysis of lipids in the herbicide-treated E. crus-galli, followed by Orthogonal Partial Least Squares Discriminant Analysis clustering. The results showed that dimesulfazet belongs to the HRAC Group 15 cluster. The endogenous concentrations of C24:0, C26:0, and C28:0 decreased in dimesulfazet-treated plants as compared to those in the control. Overall, the mode of action of dimesulfazet involves the inhibition of VLCFA biosynthesis.

Nitrogen dioxide regulates organ growth by controlling cell proliferation and enlargement in Arabidopsis.

• To gain more insight into the physiological function of nitrogen dioxide (NO2), we investigated the effects of exogenous NO2 on growth in Arabidopsis thaliana. • Plants were grown in air without NO2 for 1 wk after sowing and then grown for 1-4 wk in air with (designated treated plants) or without (control plants) NO2. Plants were irrigated semiweekly with a nutrient solution containing 19.7 mM nitrate and 10.3 mM ammonium. • Five-week-old plants treated with 50 ppb NO2 showed a ≤ 2.8-fold increase in biomass relative to controls. Treated plants also showed early flowering. The magnitude of the effects of NO2 on leaf expansion, cell proliferation and enlargement was greater in developing than in maturing leaves. Leaf areas were 1.3-8.4 times larger on treated plants than corresponding leaves on control plants. The NO2-induced increase in leaf size was largely attributable to cell proliferation in developing leaves, but was attributable to both cell proliferation and enlargement in maturing leaves. The expression of different sets of genes for cell proliferation and/or enlargement was induced by NO2, but depended on the leaf developmental stage. • Collectively, these results indicated that NO2 regulates organ growth by controlling cell proliferation and enlargement.