RESUMO
A major challenge of modern agriculture is to reduce the excessive input of fertilisers and, at the same time, to improve grain quality without affecting yield. One way to achieve this goal is to improve plant nitrogen economy through manipulating nitrogen recycling, and especially nitrogen remobilisation, from senescing plant organs. In this review, the contribution of nitrogen remobilisation efficiency (NRE) to global nitrogen use efficiency (NUE), and tools dedicated to the determination of NRE are described. An overall examination of the physiological, metabolic and genetic aspects of nitrogen remobilisation is presented.
Assuntos
Arabidopsis/metabolismo , Nitrogênio/metabolismo , Sementes/metabolismo , Arabidopsis/genética , Arabidopsis/crescimento & desenvolvimento , Transporte Biológico , Produtos Agrícolas/crescimento & desenvolvimento , Produtos Agrícolas/metabolismo , Isótopos de Nitrogênio , Folhas de Planta/genética , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/metabolismo , Locos de Características Quantitativas , Sementes/genética , Sementes/crescimento & desenvolvimentoRESUMO
Expression analyses of Nrt2 plant genes have shown a strict correlation with root nitrate influx mediated by the high-affinity transport system (HATS). The precise assignment of NRT2 protein function has not yet been possible due to the absence of heterologous expression studies as well as loss of function mutants in higher plants. Using a reverse genetic approach, we isolated an Arabidopsis thaliana knock-out mutant where the T-DNA insertion led to the complete deletion of the AtNrt2.1 gene together with the deletion of the 3' region of the AtNrt2.2 gene. This mutant is impaired in the HATS, without being modified in the low-affinity system. Moreover, the de-regulated expression of a Nicotiana plumbaginifolia Nrt2 gene restored the mutant nitrate influx to that of the wild-type. These results demonstrate that plant NRT2 proteins do have a role in HATS.
Assuntos
Proteínas de Transporte de Ânions , Proteínas de Arabidopsis , Arabidopsis/genética , Proteínas de Transporte/genética , DNA Bacteriano/genética , Nitratos/farmacocinética , Proteínas de Plantas , Arabidopsis/metabolismo , Transporte Biológico Ativo/genética , Teste de Complementação Genética , Genótipo , Cinética , Mutagênese Insercional , Mutação , Transportadores de Nitrato , Nitratos/metabolismo , Raízes de Plantas/genética , Raízes de Plantas/metabolismo , Plantas Geneticamente Modificadas , Plantas Tóxicas , Nicotiana/genéticaRESUMO
A 2.1-kb sequence was isolated by promoter trapping from an Arabidopsis thaliana transformant (T80) obtained by Agrobacterium-mediated T-DNA insertion. This sequence directed strong ß-glucuronidase (GUS) expression specifically in roots. The promoter-gus fusion was used to transform other A. thaliana plants. Most of the transformants obtained exhibited stronger GUS activity in roots than the T80 line and a weak activity in leaves with a root/leaf ratio similar to that of T80. This 2.1-kb promoter sequence possesses a high number of motifs previously described as root-specific or aspecific enhancers. However, this promoter-like sequence is not associated with a detectable transcript and its physiological significance is unclear.