12
Nitrate Transport and Signaling
Vladimir Totev Valkov and Maurizio Chiurazzi
Abstract
As sessile organisms, plants have developed a sophisticated network of
mechanisms to adapt and optimize their growth to the constantly and
rapidly changing nutritional environmental conditions. The transport of
nitrate in higher plants is a paradigm of this regulatory control as either
external or internal cues can govern the root uptake ability depending on
the nutrient demand and nitrogen availability in the soil. Plant adaptations
also include the potential to respond to changes of nitrate concentration in
the soil by modulating the root system developmental plan. It is known
that in leguminous plants, nitrate availability in the soil can also strongly
affect nodule formation as low and high concentrations exert a positive
and negative effect on initiation of the organogenesis process, respec-
tively. Nitrate can act both as a nutrient and a signal for the induction of
plant root responses, and members of the nitrate and peptide transporters
family (NPF and NRT2) play crucial roles in the control of such signaling
pathways. This chapter presents an overview of the genomic and
transcriptomic data reported for theLotus japonicus NPF andNRT2
family members, and their possible roles in the control of the nodulation
program are discussed.12.1 NPF and NRT2 Families
Nitrate transporter proteins are involved in the
control of nitrateflux from soil to root tissues and
allocation throughout the whole plant body (Miller
et al. 2007 ). Plant roots have two different uptake
systems to cope with low or highNO 3 concen-
trations in soil, the high affinity and low affinity
(HATS and LATS). Two types ofNO 3 trans-
porters, known as the NRT1 and NRT2, contribute
to LATS and HATS, respectively. The AtNRT1.1
and MtNRT1.3 proteins represent the only
exceptions as they display a dual HATS/LATS
nitrate uptake activity (Liu and Tsay 2003 ; Mor-
ère-Le Paven et al. 2011 ), although very recently
the high-affinity action of AtNRT1.1in plantawas
not confirmed as it appears to be confined to the
experimental system constituted by Xenopus
oocytes (Glass and Kotur 2013 ).V.T. ValkovM. Chiurazzi (&)
Institute of Biosciences and Bioresources, Via P.
Castellino 111, 80131 Naples, Italy
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_12,©Springer-Verlag Berlin Heidelberg 2014
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