RESUMO
Weed resistance to herbicides is a natural phenomenon that exerts selection on individuals in a population. In Brazil, glyphosate resistance was recently detected in Digitaria insularis. The objective of this study was to elucidate mechanisms of weed resistance in this plant, including genetic variability, allelism, amino acid substitutions, gene expression, and enzymatic activity levels. Most of these have not previously been studied in this species. D. insularis DNA sequences were used to analyze genetic variability. cDNA from resistant and susceptible plants was used to identify mutations, alleles, and 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) expression, using real-time quantitative reverse transcription-polymerase chain reaction. In addition, EPSPS activity was measured. We found a decrease in genetic variability between populations related to glyphosate application. Substitutions from proline to threonine and tyrosine to cysteine led to a decrease in EPSPS affinity for the glyphosate. In addition, the EPSPS enzymatic activity was slightly higher in resistant plants, whereas EPSPS gene expression was almost identical in both biotypes, suggesting feedback regulation at different levels. To conclude, our results suggest new molecular mechanisms used by D. insularis to increase glyphosate resistance.
Assuntos
3-Fosfoshikimato 1-Carboxiviniltransferase/genética , Digitaria/enzimologia , Glicina/análogos & derivados , Herbicidas/farmacologia , Proteínas de Plantas/genética , 3-Fosfoshikimato 1-Carboxiviniltransferase/metabolismo , Substituição de Aminoácidos , Digitaria/efeitos dos fármacos , Digitaria/genética , Expressão Gênica , Glicina/farmacologia , Resistência a Herbicidas , Filogenia , Proteínas de Plantas/metabolismo , Polimorfismo Genético , Análise de Sequência de DNA , GlifosatoRESUMO
UNLABELLED: Neurobrucellosis is an uncommon disease in children. The authors present two cases of brucellar meningo-encephalitis. Headache and vomiting were the main complaints and one child had also some behavioural disturbance as well as papilloedema and sixth cranial nerve palsy. The clinical diagnosis was suggested by epidemiological data in both cases. Blood and CSF cultures confirmed brucellar aetiology in one of the cases and positive serum and CSF specific antibodies in both. Clinical course was favourable after treatment with doxycycline, rifampicin and streptomycin. No relapse occurred and there were no sequelae. CONCLUSION: Neurobrucellosis should be considered in the differential diagnosis of neurobehavioural disturbance of children living in areas where brucellosis is endemic.
