The Lotus japonicus Genome

11

Genes Involved in Ammonium

Assimilation

Carmen M. Pérez-Delgado, Margarita García-Calderón,

Alfredo Credali, JoséM. Vega, Marco Betti,

and Antonio J. Márquez

Abstract

Ammonium resulting from primary nitrate reduction, dinitrogenfixation,

or nitrogen remobilization has to be efficiently assimilated. In this chapter,

we describe the main enzymes and genes responsible for ammonium

assimilation inLotus japonicusplants. We summarize the nomenclature

and codes available in Kazusa 2.5 for the main genes involved in the

ammonium assimilatory process, as well as the levels of expression found

by qRT-PCR for these genes in different tissues of the plant.

11.1 Introduction

In the model legumeLotus japonicus,different
forms of inorganic nitrogen (NO 3 −or NH 4 +) can
be taken up by the plants, depending on nitrogen
availability (Márquez et al. 2005 ; Orea et al.
2005 ). The utilization of NO 3 − requires its
reduction to NH 4 +produced by the consecutive
action of nitrate reductase and nitrite reductase
enzymes, prior to ammonium assimilation. Pre-
vious works have characterized the nitrate and
nitrite reduction systems inL. japonicus(Harrison

et al. 2004 ;Márquez et al. 2005 ; Orea et al. 2001 ;

Pajuelo et al. 2002 ; Prosser et al. 2006 ). On the

other hand,L. japonicus, as a legume plant, also

has the chance to establish symbiosis withMes-

orhizobium lotibacteria in order to use atmo-

spheric N 2 , which is reduced to NH 4 + in the

nodules by the action of bacterial nitrogenase (see

other chapters of this book). Consequently, the

process of primary ammonium assimilation,

either derived from nitrate reduction or dinitrogen

fixation, is of crucial importance inL. japonicus

plants. This is also the case for other processes

that produce an internal release of ammonium in

L. japonicus plants, such as photorespiration,

phenylpropanoid biosynthesis, or amino acid

catabolism, called in general terms secondary

ammonium assimilation (Betti et al. 2012 ;

Márquez et al. 2005 ).

In the following sections, we will describe

first the main enzymes in charge of ammonium

assimilation, basically associated with glutamine/

glutamate and asparagine metabolisms

(Sect.11.2). This is followed by the description

(Sect. 11.3) of the different genes from L.

C.M. Pérez-Delgado
M. García-Calderón

A. Credali
J.M. Vega
M. Betti
A.J. Márquez (&)
Departamento de Bioquímica Vegetal y Biología
Molecular, Facultad de Química, Universidad de
Sevilla, Calle Profesor García González, 1, 41012
Sevilla, Spain
e-mail: [email protected]

S. Tabata and J. Stougaard (eds.),The Lotus japonicus Genome, Compendium of Plant Genomes,
DOI 10.1007/978-3-662-44270-8_11,©Springer-Verlag Berlin Heidelberg 2014

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