Plants show a strong level of developmental plasticity that is controlled by a complex combination of perception, integration and response. Root system is a fantastic tool to study this plasticity since the number and position of lateral roots is deeply altered by the environment. We are trying to understand the fundamental mechanisms governing lateral root development and its control by the environment. Our research focuses on two main biological systems: the model plant Arabidopsis thaliana and white lupin (Lupinus albus).
Lateral root development
The model plant Arabidopsis thaliana has been used to study root development in great detail. This allowed to define the main stages of lateral root development : pre-initiation, initiation primordium patterning, primordium emergence and finally meristem activation (Péret et al., 2009).
The emergence stage involves cell wall remodeling in the outer tissues to facilitate teh passage of the new organ. We identified a mechanism involving the auxin influx transporter LAX3 that finely controls this process. Induction of LAX3 by auxin creates a positive feed-back loop that creates a maximum of auxin in a few cells facing the primordium. We have identified the genes controlling the induction of LAX3 (Porco et al., 2016).
Gravitropism and pre-initiation
We identified the lasso mutant that shows a strong agravitropic root growth phenotype. Interestingly, this phenotype is reverted by a combination of nutrient starvations. Additionnally, the lasso mutant displays a modification in lateral root positionning, suggesting a link between gravitropism and pre-initiation. We are trying to understand the molecular mechanisms controling this behaviour.
Cluster root early development
Cluster roots (CR) are produced in white lupin as a response to low phoshorus. They are localised in the upper part of the root system and participate to the "top-soil foraging" strategy described by Jonathan Lynch in 2001.
Cluster roots are made of hundreds of lateral roots called "rootlets". They originate from the pericycle cells in front of the xylem poles but they are massively produced with no respect towards longitudinal or radial inhibition.
Rootlets harbour a determinate mode of development. After emergence from the cluster root, they quickly differentiate up to their tip, concomitantly with the entry into senescence of the cluster. We are interested in the mechanisms leading to the activation of the genetic determinacy in the rootlet meristem.
Tools and ressources
White lupin genome: we sequenced white lupin genome and generated numerous ressources (14 varieties resequenced, numerous transcriptomic datasets, genomic analysis). They can be accessed on the White Lupin Genome portal at www.whitelupin.fr
Jérôme Gouzy and Erika Sallet - LIPM Toulouse France
Hélène Bergès and William Marande - CNRGV Toulouse France
Pierre-Marc Delaux - LRSV Toulouse France
Romain Guyot - IRD Montpellier France
Jérôme Salse - GDEC INRA Clermont-Ferrand France
Auxin transport and response
Malcolm Bennett - CPIB Nottingham UK
Tatsuaki Goh - NAIST Japan
Hidehiro Fukaki - University of Kobe Japan
Gene regulatory networks
Laurent Laplaze - IRD Montpellier
Martin Crespi and Thomas Blein - IPS2 Paris Saclay
Lupin alkaloid synthesis
Matthew Nelson - Kew Gardens UK
Fernando Geu-Flores - University of Copenhagen DK
Lupin seed quality
Karine Gallardo-Guerrero - UMR Agroécologie INRA Dijon France