Alves, Ludovico (2014) Functional characterization of molecular actors of the Nitrogen Signalling Pathways involved in the control of the Symbiotic Nitrogen Fixation. [Tesi di dottorato]

ALVES Ludovico Thesis 31032014.pdf

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Item Type: Tesi di dottorato
Resource language: English
Title: Functional characterization of molecular actors of the Nitrogen Signalling Pathways involved in the control of the Symbiotic Nitrogen Fixation
Date: 31 March 2014
Number of Pages: 150
Institution: Università degli Studi di Napoli Federico II
Department: Biologia
Scuola di dottorato: Scienze biologiche
Dottorato: Biologia applicata
Ciclo di dottorato: 26
Coordinatore del Corso di dottorato:
Chiurazzi, MaurizioUNSPECIFIED
Date: 31 March 2014
Number of Pages: 150
Keywords: Nodule organogenis, nitrate transporters, transcription factors, NPF, AP2/ERF
Settori scientifico-disciplinari del MIUR: Area 05 - Scienze biologiche > BIO/04 - Fisiologia vegetale
Date Deposited: 07 Apr 2014 15:45
Last Modified: 28 Jan 2015 09:42

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Abstract The nodulation process resulting from the symbiosis of legume roots and rhizobia allows legumes to be the major natural nitrogen-provider to the ecosystem, turning them into an economically viable replacement for fertilizers. The underlining regulatory mechanisms of nodule organogenesis have yet to be fully clarified. Nitrate has a role in nodule formation, either acting as a nutrient or a signal and its uptake soil is a critical process controlled by complex regulatory networks. In Arabidopsis thaliana various members of the NPF and NRT2 families are involved in nitrate uptake and distribution. We previously reported that various orthologous NPF and NRT2 genes of Lotus japonicus showed a repressible, inducible or constitutive response to provision of nitrate. Biochemical characterization of one of the Lotus japonicus NPF family members – LjNPF4.6 was performed through a molecular genetics approach. LjNPF4.6 has a spatial profile that matches that of a nitrate transporter and its dual-affinity transport activity was confirmed through heterologous expression in Xenopus laevis oocytes. LjNPF4.6 is necessary for proper plant recognition and uptake of high concentrations of nitrate, as shoot and root development of knock-out plants was impaired when compared with wild-type. Ethylene-responsive transcription factors of the AP2/ERF family have been shown to be regulated by nitrogen status and induced during early nodulation. LjRAP2.4 is one such transcription factors, whose orthologue in Arabidopsis is involved in many ethylene-dependent processes, such as hypocotyl development, photosynthesis control and drought stress control. In legumes, ethylene has an inhibitory effect upon nodulation, so any downstream signal of its pathway has a potential regulatory role over nodule organogenesis. Mutants overexpressing and RNAi silenced LjRAP2.4 demonstrate that LjRAP2.4 has a regulatory role in hypocotyl development in the dark and assays with the ethylene precursor ACC confirm that this role is ethylene-responsive. LjRAP2.4 is also involved in the regulation of the nodulation process, with overexpressing LjRAP2.4 plants demonstrating increased nodulation compared to wild-type.


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