RESUMO
Convolvulus arvensis is a troublesome weed that is naturally tolerant to glyphosate. This weed tolerates glyphosate at a rate 5.1 times higher than that of glyphosate-susceptible Calystegia hederacea. Glyphosate-treated C. arvensis plants accumulated less shikimic acid than C. hederacea plants. The overexpression of EPSPS genes from the two species in transgenic Arabidopsis thaliana resulted in similar glyphosate tolerance levels. qPCR of genomic DNA revealed that the EPSPS copy number in C. arvensis was approximately 2 times higher than that in C. hederacea. Moreover, glyphosate treatment caused a marked increase in EPSPS mRNA in C. arvensis compared to C. hederacea. GUS activity analysis showed that the promoter of CaEPSPS (CaEPSPS-P) highly improved GUS expression after glyphosate treatment, while no obvious differential GUS expression was observed in ChEPSPS-P transgenic A. thaliana in the presence or absence of glyphosate. Based on the obtained results, two coexisting mechanisms may explain the natural glyphosate tolerance in C. arvensis: (i) high EPSPS copy number and (ii) specific promoter-mediated overexpression of EPSPS after glyphosate treatment.
Assuntos
3-Fosfoshikimato 1-Carboxiviniltransferase/genética , Arabidopsis/efeitos dos fármacos , Calystegia/efeitos dos fármacos , Convolvulus/efeitos dos fármacos , Regulação da Expressão Gênica de Plantas , Glicina/análogos & derivados , 3-Fosfoshikimato 1-Carboxiviniltransferase/biossíntese , Arabidopsis/enzimologia , Bioensaio , Calystegia/enzimologia , Convolvulus/enzimologia , Bases de Dados Genéticas , Relação Dose-Resposta a Droga , Tolerância a Medicamentos , Glicina/química , Resistência a Herbicidas/genética , Herbicidas/química , Plantas Geneticamente Modificadas , Reação em Cadeia da Polimerase , Pós , Regiões Promotoras Genéticas , Ácido Chiquímico/metabolismo , GlifosatoRESUMO
Interactions between heavy metals, glutathione, glutathione S-transferase (GST), and glutathione reductase (GR) are being investigated by many working groups, but evaluation of the direct effect of Cd+ on these enzymes in vitro is lacking. We report here the effect of cadmium (10, 50, 100, 250 microM CdSO4) on partially purified enzymes from Calystegia sepium. Plants were grown under normal field conditions without metals and the enzymes were extracted by Tris buffer and partially purified by ammonium sulphate fractionation and gel filtration. Glutathione S-transferase activity was measured with different substrates, i.e., 1-chloro-2,4-dinitrobenzene (CDNB), p-nitrobenzylchloride (NBC), and the herbicide Fluorodifen. GST activity was significantly lower in leaf compared to stem, flower, and rhizome and the inhibitory effect of Cd was obtained with NBC and Fluorodifen substrates at 250 microM. There was no effect of Cd on GR activity up to 250 microM.
