The Arabidopsis nitrate transporter NRT2.5 plays a role in nitrate acquisition and remobilization in nitrogen-starved plants

AbstractPlants are very effective in responding to environmental changes during competition for light and nutrients. Low Red:Far-Red (low R:FR)-mediated neighbor detection allows plants to compete successfully with other plants for available light. This above-ground signal can also reduce lateral root growth by inhibiting lateral root emergence, a process that might help the plant invest resources in shoot growth. Nitrate is an essential nutrient for plant growth and Arabidopsis thaliana responds to low nitrate conditions by enhancing nutrient uptake and reducing lateral and main root growth. There are indications that low R:FR signaling and low nitrate signaling can affect each other. It is unknown which response is prioritized when low R:FR light- and low nitrate signaling co-occur. We investigated the effect of low nitrate conditions on the low R:FR response of the A. thaliana root system in agar plate media, combined with the application of supplemental Far-Red (FR) light to the shoot. We observed that under low nitrate conditions main and lateral root growth was reduced, but more importantly, that the response of the root system to low R:FR was suppressed. Consistently, a loss-of-function mutant of a nitrate transporter gene NRT2.1 lacked low R:FR-induced lateral root reduction and its root growth was hypersensitive to low nitrate. ELONGATED HYPOCOTYL5 (HY5) plays an important role in the root response to low R:FR and we found that it was less sensitive to low nitrate conditions with regards to lateral root growth. In addition, we found that low R:FR increases NRT2.1 expression and that low nitrate enhances HY5 expression. HY5 also affects NRT2.1 expression, however, it depended on the presence of ammonium in which direction this effect was. Replacing part of the nitrogen source with ammonium also removed the effect of low R:FR on the root system, showing that changes in nitrogen sources can be crucial for root plasticity. Together our results show that nitrate signaling can repress low R:FR responses and that this involves signaling via HY5 and NRT2.1.

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Genome-wide identification and analyses of tomato (Solanum lycopersicum L.) high-affinity nitrate transporter 2 (NRT2) family genes and their responses to drought and salinity

10.1101/2021.12.08.471831 ◽

2021 ◽

Author(s):

M. AYDIN AKBUDAK ◽

Ertugrul Filiz ◽

Durmus Cetin

Keyword(s):

Solanum Lycopersicum ◽

Expression Profiles ◽

Gene Families ◽

Major Facilitator Superfamily ◽

Nitrate Transporter ◽

Tomato Genome ◽

High Affinity ◽

Solanum Lycopersicum L ◽

Major Facilitator ◽

Systematic Identification

High-affinity nitrate transporter 2 (NRT2) proteins have vital roles in nitrate (NO3-) uptake and translocation in plants. The gene families coding NRT2 proteins have been identified and functionally characterized in many plant species. However, no systematic identification of NRT2 family members have been reported in tomato (Solanum lycopersicum). There is also little known about their expression profiles under environmental stresses. Accordingly, the present study aimed to identify NRT2 gene family in the tomato genome; then, investigate them in detail through bioinformatics, physiological and expression analyses. As a result, four novel NRT2 genes were identified in the tomato genome, all of which contain the same domain belonging to the Major Facilitator Superfamily (PF07690). The co-expression network of SlNRT genes revealed that they were co-expressed with several other genes in many different molecular pathways including transport, photosynthesis, fatty acid metabolism and amino acid catabolism. Programming many crucial physiological and metabolic pathways, various numbers of phosphorylation sites were predicted in the NRT2 proteins.

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Phylogenomic and Microsynteny Analysis Provides Evidence of Genome Arrangements of High-Affinity Nitrate Transporter Gene Families of Plants

International Journal of Molecular Sciences ◽

10.3390/ijms222313036 ◽

2021 ◽

Vol 22 (23) ◽

pp. 13036

Author(s):

Normig M. Zoghbi-Rodríguez ◽

Samuel David Gamboa-Tuz ◽

Alejandro Pereira-Santana ◽

Luis C. Rodríguez-Zapata ◽

Lorenzo Felipe Sánchez-Teyer ◽

...

Keyword(s):

Functional Characterization ◽

Nitrate Assimilation ◽

Gene Families ◽

Land Plants ◽

Nitrate Transport ◽

Phylogenomic Analysis ◽

Evolutionary Constraint ◽

N Availability ◽

Nitrate Transporter ◽

High Affinity

Nitrate transporter 2 (NRT2) and NRT3 or nitrate-assimilation-related 2 (NAR2) proteins families form a two-component, high-affinity nitrate transport system, which is essential for the acquisition of nitrate from soils with low N availability. An extensive phylogenomic analysis across land plants for these families has not been performed. In this study, we performed a microsynteny and orthology analysis on the NRT2 and NRT3 genes families across 132 plants (Sensu lato) to decipher their evolutionary history. We identified significant differences in the number of sequences per taxonomic group and different genomic contexts within the NRT2 family that might have contributed to N acquisition by the plants. We hypothesized that the greater losses of NRT2 sequences correlate with specialized ecological adaptations, such as aquatic, epiphytic, and carnivory lifestyles. We also detected expansion on the NRT2 family in specific lineages that could be a source of key innovations for colonizing contrasting niches in N availability. Microsyntenic analysis on NRT3 family showed a deep conservation on land plants, suggesting a high evolutionary constraint to preserve their function. Our study provides novel information that could be used as guide for functional characterization of these gene families across plant lineages.

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