Limits...
Plant Nitrogen Acquisition Under Low Availability: Regulation of Uptake and Root Architecture.

Kiba T, Krapp A - Plant Cell Physiol. (2016)

Bottom Line: One of the most important responses is the regulation of nitrogen acquisition efficiency.This review provides an update on the molecular determinants of two major drivers of the nitrogen acquisition efficiency: (i) uptake activity (e.g. high-affinity nitrogen transporters) and (ii) root architecture (e.g. low-nitrogen-availability-specific regulators of primary and lateral root growth).Major emphasis is laid on the regulation of these determinants by nitrogen supply at the transcriptional and post-transcriptional levels, which enables plants to optimize nitrogen acquisition efficiency under low nitrogen availability.

View Article: PubMed Central - PubMed

Affiliation: RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro, Tsurumi, Yokohama, 230-0045 Japan takatoshi.kiba@riken.jp anne.krapp@versailles.inra.fr.

No MeSH data available.


Schematic illustration summarizing the function of NRT2 transporters in Arabidopsis roots under low N availability. Spatial and temporal localization of AtNRT2.1 (NRT2.1, purple), AtNRT2.4 (NRT2.4, blue) and AtNRT2.5 (NRT2.5, red) in (A) root tissues and (B) whole root systems under low N availability. (A) The NRT2.4/NAR2 complex is localized to the outer (soil) side of the epidermal cells of the roots of young seedlings. The NRT2.5/NAR2 complex is expressed in the epidermal cells of the roots of adult plants. NRT2.4 and NRT2.5 are responsible for nitrate uptake directly from the soil. Nitrate can apoplastically penetrate toward cortex cells to be absorbed by the NRT2.1/NAR2 complex. NAR2 (AtNAR2.1) is shown as green circles. Orange circles indicate a putative high-affinity exporter involved in xylem loading of nitrate. (B) NRT2.1 is strongly expressed in the older part of the root system, while NRT2.4 and NRT2.5 are preferentially expressed in the younger part of the roots of young seedlings and adult plants, respectively. ep, epidermis; co, cortex; en, endodermis; pe, pericycle; xy, xylem; cs, casparian strip
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4836452&req=5

pcw052-F1: Schematic illustration summarizing the function of NRT2 transporters in Arabidopsis roots under low N availability. Spatial and temporal localization of AtNRT2.1 (NRT2.1, purple), AtNRT2.4 (NRT2.4, blue) and AtNRT2.5 (NRT2.5, red) in (A) root tissues and (B) whole root systems under low N availability. (A) The NRT2.4/NAR2 complex is localized to the outer (soil) side of the epidermal cells of the roots of young seedlings. The NRT2.5/NAR2 complex is expressed in the epidermal cells of the roots of adult plants. NRT2.4 and NRT2.5 are responsible for nitrate uptake directly from the soil. Nitrate can apoplastically penetrate toward cortex cells to be absorbed by the NRT2.1/NAR2 complex. NAR2 (AtNAR2.1) is shown as green circles. Orange circles indicate a putative high-affinity exporter involved in xylem loading of nitrate. (B) NRT2.1 is strongly expressed in the older part of the root system, while NRT2.4 and NRT2.5 are preferentially expressed in the younger part of the roots of young seedlings and adult plants, respectively. ep, epidermis; co, cortex; en, endodermis; pe, pericycle; xy, xylem; cs, casparian strip

Mentions: Among seven NRT2 genes in Arabidopsis, AtNRT2.1, AtNRT2.2, AtNRT2.4 and AtNRT2.5 are expressed in the roots of N-deprived plants. Analysis of a quadruple mutant revealed that these four NRT2 transporters account for approximately 95% of high-affinity nitrate influx activity under N limitation, AtNRT2.1 being the major contributor (Lezhneva et al. 2014). Recent studies suggest that the spatio-temporal distribution of these four AtNRT2 transporters is critical for efficient nitrate uptake to sustain growth under low N availability (Fig. 1; Kiba et al. 2012, Lezhneva et al. 2014). During N deprivation, the expression of AtNRT2.1 is transiently derepressed in the cortex cells of older parts of primary and lateral roots (Wirth et al. 2007). In contrast, the transcript levels of AtNRT2.4 and AtNRT2.5 increase during N deprivation over time in the epidermal cells of young primary and lateral roots (Kiba et al. 2012, Lezhneva et al. 2014, Kotur and Glass 2015). These spatial expression patterns indicate that AtNRT2.4 and AtNRT2.5 are responsible for nitrate uptake from the soil, and AtNRT2.1 plays a role in apoplastic nitrate absorption. Although AtNRT2.4 and AtNRT2.5 are expressed in the same cell types, the former is predominant in young seedlings and the latter in adult plants (Fig. 1; Kiba et al. 2012, Lezhneva et al. 2014). In addition, AtNRT2.4 was suggested to have much higher affinity for nitrate than AtNRT2.1 (Kiba et al. 2012). Although a dual-affinity transporter AtNPF6.3 is also expressed in roots under N limitation, its direct contribution to high-affinity nitrate transport under N limitation seems to be minor, maybe even non-existent (Glass and Kotur 2013). The existence of a high-affinity efflux transport system for xylem loading of nitrate (Fig. 1A) has been suggested from the phenotype of atnrt1.5, which is a mutant of a low-affinity efflux transporter responsible for xylem loading of nitrate (Lin et al. 2008). However, the transporter gene(s) involved in the system is(are) still unknown.Fig. 1


Plant Nitrogen Acquisition Under Low Availability: Regulation of Uptake and Root Architecture.

Kiba T, Krapp A - Plant Cell Physiol. (2016)

Schematic illustration summarizing the function of NRT2 transporters in Arabidopsis roots under low N availability. Spatial and temporal localization of AtNRT2.1 (NRT2.1, purple), AtNRT2.4 (NRT2.4, blue) and AtNRT2.5 (NRT2.5, red) in (A) root tissues and (B) whole root systems under low N availability. (A) The NRT2.4/NAR2 complex is localized to the outer (soil) side of the epidermal cells of the roots of young seedlings. The NRT2.5/NAR2 complex is expressed in the epidermal cells of the roots of adult plants. NRT2.4 and NRT2.5 are responsible for nitrate uptake directly from the soil. Nitrate can apoplastically penetrate toward cortex cells to be absorbed by the NRT2.1/NAR2 complex. NAR2 (AtNAR2.1) is shown as green circles. Orange circles indicate a putative high-affinity exporter involved in xylem loading of nitrate. (B) NRT2.1 is strongly expressed in the older part of the root system, while NRT2.4 and NRT2.5 are preferentially expressed in the younger part of the roots of young seedlings and adult plants, respectively. ep, epidermis; co, cortex; en, endodermis; pe, pericycle; xy, xylem; cs, casparian strip
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4836452&req=5

pcw052-F1: Schematic illustration summarizing the function of NRT2 transporters in Arabidopsis roots under low N availability. Spatial and temporal localization of AtNRT2.1 (NRT2.1, purple), AtNRT2.4 (NRT2.4, blue) and AtNRT2.5 (NRT2.5, red) in (A) root tissues and (B) whole root systems under low N availability. (A) The NRT2.4/NAR2 complex is localized to the outer (soil) side of the epidermal cells of the roots of young seedlings. The NRT2.5/NAR2 complex is expressed in the epidermal cells of the roots of adult plants. NRT2.4 and NRT2.5 are responsible for nitrate uptake directly from the soil. Nitrate can apoplastically penetrate toward cortex cells to be absorbed by the NRT2.1/NAR2 complex. NAR2 (AtNAR2.1) is shown as green circles. Orange circles indicate a putative high-affinity exporter involved in xylem loading of nitrate. (B) NRT2.1 is strongly expressed in the older part of the root system, while NRT2.4 and NRT2.5 are preferentially expressed in the younger part of the roots of young seedlings and adult plants, respectively. ep, epidermis; co, cortex; en, endodermis; pe, pericycle; xy, xylem; cs, casparian strip
Mentions: Among seven NRT2 genes in Arabidopsis, AtNRT2.1, AtNRT2.2, AtNRT2.4 and AtNRT2.5 are expressed in the roots of N-deprived plants. Analysis of a quadruple mutant revealed that these four NRT2 transporters account for approximately 95% of high-affinity nitrate influx activity under N limitation, AtNRT2.1 being the major contributor (Lezhneva et al. 2014). Recent studies suggest that the spatio-temporal distribution of these four AtNRT2 transporters is critical for efficient nitrate uptake to sustain growth under low N availability (Fig. 1; Kiba et al. 2012, Lezhneva et al. 2014). During N deprivation, the expression of AtNRT2.1 is transiently derepressed in the cortex cells of older parts of primary and lateral roots (Wirth et al. 2007). In contrast, the transcript levels of AtNRT2.4 and AtNRT2.5 increase during N deprivation over time in the epidermal cells of young primary and lateral roots (Kiba et al. 2012, Lezhneva et al. 2014, Kotur and Glass 2015). These spatial expression patterns indicate that AtNRT2.4 and AtNRT2.5 are responsible for nitrate uptake from the soil, and AtNRT2.1 plays a role in apoplastic nitrate absorption. Although AtNRT2.4 and AtNRT2.5 are expressed in the same cell types, the former is predominant in young seedlings and the latter in adult plants (Fig. 1; Kiba et al. 2012, Lezhneva et al. 2014). In addition, AtNRT2.4 was suggested to have much higher affinity for nitrate than AtNRT2.1 (Kiba et al. 2012). Although a dual-affinity transporter AtNPF6.3 is also expressed in roots under N limitation, its direct contribution to high-affinity nitrate transport under N limitation seems to be minor, maybe even non-existent (Glass and Kotur 2013). The existence of a high-affinity efflux transport system for xylem loading of nitrate (Fig. 1A) has been suggested from the phenotype of atnrt1.5, which is a mutant of a low-affinity efflux transporter responsible for xylem loading of nitrate (Lin et al. 2008). However, the transporter gene(s) involved in the system is(are) still unknown.Fig. 1

Bottom Line: One of the most important responses is the regulation of nitrogen acquisition efficiency.This review provides an update on the molecular determinants of two major drivers of the nitrogen acquisition efficiency: (i) uptake activity (e.g. high-affinity nitrogen transporters) and (ii) root architecture (e.g. low-nitrogen-availability-specific regulators of primary and lateral root growth).Major emphasis is laid on the regulation of these determinants by nitrogen supply at the transcriptional and post-transcriptional levels, which enables plants to optimize nitrogen acquisition efficiency under low nitrogen availability.

View Article: PubMed Central - PubMed

Affiliation: RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro, Tsurumi, Yokohama, 230-0045 Japan takatoshi.kiba@riken.jp anne.krapp@versailles.inra.fr.

No MeSH data available.