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The nitrate transporter NRT2.1 directly antagonizes PIN7-mediated auxin transport for root growth adaptation.

ABSTRACT: As a crucial nitrogen source, nitrate (NO₃^-) is a key nutrient for plants. Accordingly, root systems adapt to maximize NO₃^- availability, a developmental regulation also involving the phytohormone auxin. Nonetheless, the molecular mechanisms underlying this regulation remain poorly understood. Here, we identify low-nitrate-resistant mutant (lonr) in Arabidopsis (Arabidopsis thaliana), whose root growth fails to adapt to low-NO₃^- conditions. lonr2 is defective in the high-affinity NO₃^- transporter NRT2.1. lonr2 (nrt2.1) mutants exhibit defects in polar auxin transport, and their low-NO₃^--induced root phenotype depends on the PIN7 auxin exporter activity. NRT2.1 directly associates with PIN7 and antagonizes PIN7-mediated auxin efflux depending on NO₃^- levels. These results reveal a mechanism by which NRT2.1 in response to NO₃^- limitation directly regulates auxin transport activity and, thus, root growth. This adaptive mechanism contributes to the root developmental plasticity to help plants cope with changes in NO₃^- availability.

SUBMITTER: Wang Y

PROVIDER: S-EPMC10288568 | biostudies-literature | 2023 Jun

REPOSITORIES: biostudies-literature

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The nitrate transporter NRT2.1 directly antagonizes PIN7-mediated auxin transport for root growth adaptation.

Wang Yalu Y Yuan Zhi Z Wang Jinyi J Xiao Huixin H Wan Lu L Li Lanxin L Guo Yan Y Gong Zhizhong Z Friml Jiří J Zhang Jing J

Proceedings of the National Academy of Sciences of the United States of America 20230612 25

As a crucial nitrogen source, nitrate (NO3-) is a key nutrient for plants. Accordingly, root systems adapt to maximize NO3- availability, a developmental regulation also involving the phytohormone auxin. Nonetheless, the molecular mechanisms underlying this regulation remain poorly understood. Here, we identify low-nitrate-resistant mutant (lonr) in Arabidopsis (Arabidopsis thaliana), whose root growth fails to adapt to low-NO ...[more]

PMID: 37307446

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Project description:Plants 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 not present. 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.

Dataset Information

The nitrate transporter NRT2.1 directly antagonizes PIN7-mediated auxin transport for root growth adaptation.

Publications

The nitrate transporter NRT2.1 directly antagonizes PIN7-mediated auxin transport for root growth adaptation.

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