title: Transcriptomic analysis highlights reciprocal interactions of urea and nitrate for nitrogen acquisition by maize roots.
abstract: Even though urea and nitrate are the two major nitrogen (N) forms applied as fertilizers in agriculture and occur concomitantly in soils, the reciprocal influence of these two N sources on the mechanisms of their acquisition are poorly understood. Therefore, molecular and physiological aspects of urea and nitrate uptake were investigated in maize (Zea mays), a crop plant consuming high amounts of N. In roots, urea uptake was stimulated by the presence of urea in the external solution, indicating the presence of an inducible transport system. On the other hand, the presence of nitrate depressed the induction of urea uptake and, at the same time, the induction of nitrate uptake was depressed by the presence of urea. The expression of about 60,000 transcripts of maize in roots was monitored by microarray analyses and the transcriptional patterns of those genes involved in nitrogen acquisition were analyzed by real-time reverse transcription-PCR (RT-PCR). In comparison with the treatment without added N, the exposure of maize roots to urea modulated the expression of only very few genes, such as asparagine synthase. On the other hand, the concomitant presence of urea and nitrate enhanced the overexpression of genes involved in nitrate transport (NRT2) and assimilation (nitrate and nitrite reductase, glutamine synthetase 2), and a specific response of 41 transcripts was determined, including glutamine synthetase 1-5, glutamine oxoglutarate aminotransferase, shikimate kinase and arogenate dehydrogenase. Also based on the real-time RT-PCR analysis, the transcriptional modulation induced by both sources might determine an increase in N metabolism promoting a more efficient assimilation of the N that is taken up.
authors.affiliation: Dipartimento di Scienze Agrarie e Ambientali, University of Udine, via delle Scienze 208, I-33100 Udine, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Zanin
authors.affiliation: Dipartimento di Biotecnologie, University of Verona, Ca' Vignal 1- Strada Le Grazie 15, I-37134 Verona, Italy.
authors.forename: Anita
authors.initials: A
authors.lastname: Zamboni
authors.affiliation: Dipartimento di Scienze Agrarie e Ambientali, University of Udine, via delle Scienze 208, I-33100 Udine, Italy.
authors.forename: Rossella
authors.initials: R
authors.lastname: Monte
authors.affiliation: Dipartimento di Scienze Agrarie e Ambientali, University of Udine, via delle Scienze 208, I-33100 Udine, Italy.
authors.forename: Nicola
authors.initials: N
authors.lastname: Tomasi
authors.affiliation: Dipartimento di Biotecnologie, University of Verona, Ca' Vignal 1- Strada Le Grazie 15, I-37134 Verona, Italy.
authors.forename: Zeno
authors.initials: Z
authors.lastname: Varanini
authors.affiliation: Faculty of Science and Technology, Free University of Bolzano, Piazza Università 5, I-39100 Bolzano, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Cesco
authors.affiliation: Dipartimento di Scienze Agrarie e Ambientali, University of Udine, via delle Scienze 208, I-33100 Udine, Italy roberto.pinton@uniud.it.
authors.forename: Roberto
authors.initials: R
authors.lastname: Pinton
mesh_terms: D001692:Biological Transport / Q000187:drug effects / Q000235:genetics; D018533:Biomass; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D009566:Nitrates / Q000378:metabolism* / Q000494:pharmacology; D009584:Nitrogen / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism; D018520:Plant Shoots / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D014158:Transcription, Genetic / Q000187:drug effects; D059467:Transcriptome / Q000187:drug effects / Q000235:genetics*; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics; D014508:Urea / Q000378:metabolism* / Q000494:pharmacology; D003313:Zea mays / Q000187:drug effects / Q000235:genetics*
chemical_list: D009566:Nitrates; D012333:RNA, Messenger; D014508:Urea; D009584:Nitrogen
keywords: Gene expression; High-affinity transport system; Nitrogen metabolism; Nitrogen uptake; Zea mays L