RESUMO
The herbicide 2,4-D exhibits an auxinic activity and therefore can be used as a synthetic and traceable analog to study auxin-related responses. Here we identified that not only exogenous 2,4-D but also its amide-linked metabolite 2,4-D-Glu displayed an inhibitory effect on plant growth via the TIR1/AFB auxin-mediated signaling pathway. To further investigate 2,4-D metabolite conversion, identity and activity, we have developed a novel purification procedure based on the combination of ion exchange and immuno-specific sorbents combined with a sensitive liquid chromatography-mass spectrometry method. In 2,4-D treated samples, 2,4-D-Glu and 2,4-D-Asp were detected at 100-fold lower concentrations compared to 2,4-D levels, showing that 2,4-D can be metabolized in the plant. Moreover, 2,4-D-Asp and 2,4-D-Glu were identified as reversible forms of 2,4-D homeostasis that can be converted to free 2,4-D. This work paves the way to new studies of auxin action in plant development.
Assuntos
Ácido 2,4-Diclorofenoxiacético/farmacologia , Arabidopsis/metabolismo , Ácidos Indolacéticos/metabolismo , Raízes de Plantas/metabolismo , Arabidopsis/efeitos dos fármacos , Arabidopsis/crescimento & desenvolvimento , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Proteínas F-Box/genética , Proteínas F-Box/metabolismo , Regulação da Expressão Gênica de Plantas , Herbicidas/farmacologia , Homeostase , Reguladores de Crescimento de Plantas/farmacologia , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/crescimento & desenvolvimento , Receptores de Superfície Celular/genética , Receptores de Superfície Celular/metabolismo , Plântula/efeitos dos fármacos , Plântula/crescimento & desenvolvimento , Plântula/metabolismo , Transdução de Sinais/efeitos dos fármacosRESUMO
Hydroxycinnamates are common phenolic compounds of plants and plant foods, often found in substantial quantities. Due to their high in vitro antioxidant activity they can easily be oxidized under oxidative conditions. In this study, we found that in vitro oxidation of coumaric, ferulic and sinapic acids resulted mainly in dimeric compounds. We hypothesized that these dimers are present in plants and plant foods not only in their bound form but also as free acids that can be extracted from non-hydrolyzed samples. By applying sensitive UHPLC-MS/MS method, we were able to identify and quantify four free hydroxycinnamic acid dimers for the first time, namely 8-8'-disinapic, 8-5'-diferulic, 8-O-4'-diferulic and 8-3'-dicoumaric acids, in wheat sprouts, Chinese cabbage, millet sprouts, light beer and parsley. Concentrations of dicinnamates in plant tissues ranged from 0.05 to 2.8 µg g(-1) DW and the monomer:dimer ratio ranged from 2 to 850.
