Blanc SVSE 6 - Blanc - SVSE 6 - Génomique, génétique, bioinformatique et biologie systémique

Genetics and integrative biology of plant root hydraulics – HydroRoot

Water transport in plant roots : which genetic bases ?

It is crucial to understand the genetic and molecular factors that determine the capacity of roots to take up soil water, to gain a fundamental knowledge of this process but also to foster crop improvement.

Molecular and genetic mechanisms that determine the hydraulic characteristics of plant roots

Because of global changes and an increasing demand in food worldwide, it has become crucial to understand how plants absorb and use soil water. The HydroRoot project aims at increasing our fundamental knowledge of root water transport. It will lead to an integrated view of the root, taking into account both the tissue hydraulic properties and the root architecture, and explaining how these components are controlled at the molecular level by physiological and environmental cues. Because of its strength in physiology and genetics, this research may also help improve crop selection procedures, to produce plants with improved water usage and stress responses.

The HydroRoot project will use a novel combination of approaches in the model plant Arabidopsis thaliana : accurate biophysical measurements will be coupled to mathematical modeling and genetic approaches to deliver an integrative view of plant root hydraulics.
More specifically, aquaporins are water channel proteins that facilitate the transport of water across cell membranes. The differentiation of cell walls and xylem vessels can also determine root hydraulic properties. A first approach, based on reverse genetics, will help determine the various molecular components of root hydraulics. Another strategy will be to identify Quantitative Trait Loci (QTLs) and clone novel genes controlling the root water transport capacity. Although it remains technically challenging, this innovative approach was made possible through the recent development, by one partner, of a semi-automatized hydraulic phenotyping device. In addition, a significant variation of root hydraulics was recently uncovered among natural accessions of Arabidopsis. Finally, a complementary mathematical modeling approach will be developed, to properly interpret the various root water transport phenotypes identified in the genetic approaches. Modeling will allow integrating at the whole root level the function of aquaporins and of other molecular components involved in radial and/or axial water transport.

A first hydraulic model of the Arabidopsis root was produced.
In addition, we established that a dissection of plant root hydraulics by quantitative genetics is feasible.

The HydroRoot project will explore as yet unknown facets of root water transport. It will lead to an integrative view of this process, taking into account the tissue hydraulic properties and the architecture of the whole root system. It may ultimately explain how these components are controlled at the molecular level by the physiological status of the plant and/or environmental factors.

en cours

In the context of global change and increasing demand in food production, understanding how plants absorb and use water has become a fundamental issue worldwide. The HydroRoot project proposes a unique combination of approaches in the model plant Arabidopsis thaliana to enhance our fundamental knowledge of root water transport. Accurate biophysical measurements and mathematical modelling will be used, in support of reverse and quantitative genetics approaches, to produce an integrated view of root hydraulics.

Aquaporins are water channel proteins that contribute to water transport across cell membranes. The differentiation of cell wall barriers (e.g. Casparian band) or xylem vessels is also thought to determine root hydraulics. To address the various molecular components involved, a broad reverse genetics approach will be developed. The intraspecific natural variation of plant hydraulics will also be exploited. The main objective will be to identify QTLs and clone new (and possibly unexpected) quantitative trait genes (QTGs) controlling root water transport capacity. We believe that this innovative, and therefore demanding approach has become feasible because of the recent development by one partner of a semi-automatic hydraulic phenotyping device with enhanced throughput. In addition, a significant genetic variation of root hydraulics in a selected set of natural accessions was recently described.

A modelling approach will be developed as an essential support, for proper interpretation of the various root water transport phenotypes uncovered in the two genetic approaches. Modelling will ultimately integrate within the whole root the function of aquaporins and other molecular components involved in radial or axial water transport. For this, we will link experimental water transport data with theoretical models and will integrate, within an anatomical representation of the root, flux equations for water. More specifically, a local composite model of radial water transport will be integrated into root architecture, to address the emerging properties of whole root hydraulics.

The HydroRoot project will be made possible by the assembly of three participating groups with outstanding achievements in three distinct and complementary fields of expertise, and shared interests in plant water relations and/or root functions. The group led by C. Maurel is internationally acknowledged for its work on the molecular physiology of membrane water transport and plant responses to abiotic stresses. It has developed a unique set of biophysical techniques for accurately measuring water transport in the root of various Arabidopsis genotypes. These techniques will be crucial for hydraulic phenotyping of the various genetic materials studied in the project. The group of O. Loudet has an outstanding reputation in quantitative genetics and also addresses the mechanisms of abiotic stress tolerance. This group will bring in its unique expertise for efficient QTG cloning. The group of C. Godin has realized landmark studies on the modelling of root anatomy and growth. It will now integrate hydraulic properties to yield a fully integrated functional model of the root.

The HydroRoot project will therefore address as yet unknown facets of root water transport. It will lead to an integrated view of root hydraulics that considers both tissue hydraulics and root architecture and explains how these components are controlled at the molecular level by physiological and/or environmental cues. Because of its strong physiological and genetic background, this research may also directly impact on breeding programmes, for production of crops with optimised water usage and stress responses.

Project coordination

Christophe MAUREL (CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE - DELEGATION REGIONALE LANGUEDOC-ROUSSILLON) – maurel@supagro.inra.fr

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

CNRS-BPMP CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE - DELEGATION REGIONALE LANGUEDOC-ROUSSILLON
INRA-IJPB INSTITUT NATIONAL DE LA RECHERCHE AGRONOMIQUE - CENTRE DE RECHERCHE DE VERSAILLES GRIGNON
CIRAD-AGAP CENTRE DE COOPERATION INTERNATIONALE EN RECHERCHE AGRONOMIQUE POUR LE DEVELOPPEMENT - CIRAD - DEPARTEMENT BIOS

Help of the ANR 287,999 euros
Beginning and duration of the scientific project: February 2012 - 36 Months

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