CE20 - Biologie des animaux, des organismes photosynthétiques et des microorganismes

Adjusting nitrate fluxes in plant growth responses to shade or temperature – NitReST

Submission summary

Plants constantly adjust their development in response to variations of environmental parameters, both above and below ground. How do plants sense and integrate various concomitant external signals? How does each signal influence the response to another? These questions are at the heart of the NitReST project, in which I will address the interplay between plant nutrition and growth responses to light or temperature.
Nitrogen is one of the most important nutrients for plant growth and development. In temperate aerobic soils, nitrate ions (NO3-) are the main source of nitrogen for many plant species and roots are exposed to large variations of nitrate availability. To ensure high crop yields, nitrate-based fertilizers are supplied in large excess in agricultural soils. However, such excess is transient due to depletion by roots and leakage, which has potentially harmful consequences for the environment. It is crucial to understand how plants deal with nitrate supply and how it affects their development, especially in constraining environments. A good example of such challenging situations is the shade of competitive neighbours. In some species like Arabidopsis thaliana, unfavourable light conditions lead to elongation of vegetative aerial organs like hypocotyls but a restriction of root growth. This response, known as the shade-avoidance syndrome (SAS), helps plants overtop competitors and get better access to sunlight. Similarly, a slight elevation of ambient temperature like those associated with the current climate change also triggers a developmental response called thermomorphogenesis that includes hypocotyl elongation. The phenotypic consequences as well as the underlying signalling pathways are highly similar to SAS. Nonetheless, contrary to SAS, higher temperatures favour root elongation. This difference may have an impact on how plants can take up available nutrients from soil in both contexts.
The NitReST project aims at deciphering how plants integrate nitrate nutrition and growth responses to shade or elevated ambient temperature. The main hypothesis is that nitrate fluxes are regulated in seedlings upon perception of a shade signal or high temperature and a sufficient soil nitrate concentration is required to ensure hypocotyl and root elongation in these contexts. NitReST will tackle this issue by answering two complementary questions. First, I will address how light or temperature conditions affect nitrate uptake, transport and assimilation in young seedlings. To do so, I will combine metabolomics experiments with a reverse genetics approach to (1) understand how the different steps of nitrate homeostasis are regulated in SAS and thermomorphogenesis and (2) identify key players of the nitrate pathway involved in environment-driven growth responses. Second, I will determine how nitrate availability impacts hypocotyl and root elongation in young seedlings in response to shade or elevated temperature. The thorough phenotyping with combined treatments will be followed by two complementary approaches (GWAS and comparative transcriptomics) to describe the natural variation underlying the interactions between shade/temperature and nitrate supply and identify regulators of this interplay.
One originality of the approach will be to combine the use of Arabidopsis thaliana as the main model species to new emerging models from the Brassicaceae family: Brassica rapa and Cardamine hirsuta. Both are close relatives to Arabidopsis, with their genome sequenced, the possibility to get mutant by CRISPR technology, and they display contrasted responses to shade or temperature. This will allow me to understand how [NO3-] affects species with different strategies towards shade or high temperature.
The outcomes of the NitReST project will have a strong impact for both fundamental and applied research as they will bring new insights to how to optimize the use of nitrate fertilizers in the context of dense environments and climate change.

Project coordinator

Madame Anne-Sophie Fiorucci (Institut de Biologie Intégrative de la Cellule)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

I2BC Institut de Biologie Intégrative de la Cellule

Help of the ANR 367,457 euros
Beginning and duration of the scientific project: December 2021 - 48 Months

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