Thierry Simonneau - Research Director INRAE

My research activities in plant ecophysiology aim at maintaining or even improving plant production in a context of increasing climatic constraints and competition for water use. Thus, to better understand the impact of climatic constraints on plant production, I am developing two lines of research.

> First, I study the mechanisms of water transfer regulation through the plant, either at the root level (i.e. absorption [5]) or at the leaf level (i.e. transpiration [6]).
> Secondly, I analyze the role of fluctuations in tissue water status in the response of organ growth to climatic variations [4, 10].
I have conducted work on many species (peach, poplar, sunflower, maize [3,4] Arabidopis [7,8]), but most of my current activities concern grapevine [9].
My approach combines biophysical approaches of ecophysiology with genetic approaches and biochemical and molecular approaches. I rely heavily on modeling to (i) structure existing knowledge, (ii) plan experiments with respect to hypotheses to be tested, (iii) analyze the results, and finally reintegrate them into dynamic models. Thanks to these approaches, I feed the models of plant response to the climatic environment, used by my collaborators at LEPSE for the analysis of genetic variability and the definition of ideotypes adapted to constraining climatic scenarios. I coordinated one of the first studies demonstrating that it was possible to represent in a mathematical model the impact at the level of the whole plant of the genetic variability generated on an elementary mechanism (the capacity to synthesize absicissic acid) by genetic manipulation.
During the last few years, my work has mainly led to highlight :
    > the integrated role of a hormone (abscisic acid [11]) and several genes (aquaporins [3,4], shaker-type potassium channels [1,2]) in stomatal function and transpiration regulation ;
    > the importance of the spatial organization of young leaves and hormonal signaling in the acquisition of stomatal competence to respond to water deficit conditions [12] ;
    > the evolution of hydraulic and metabolic limitations to growth as a function of leaf development stage [7] ;
    > the importance of fluctuations in cell turgor in expanding tissues [3,4,7] in understanding plant response to soil drying and fluctuations in evaporative demand.
Currently, I am pursuing my work on the regulation of plant growth under water deficit. In particular, I analyze the processes that regulate turgor in growing cells. I am developing studies on the control of water flow by investigating the origin of the differences in the functioning of isohydric and anisohydric plants in the Vitis species. With the members of my team, my objectives are to specify the genetic and agronomic margins of manoeuvre to improve transpiration efficiency in grapevine [9].

Main publications since 2008 :

    [1]      Lebaudy A., Vavasseur A., Hosy E., Dreyer I., Leonhardt N., Thibaud J.-B., Véry A.-A.,Simonneau T., Sentenac H. (2008) Plant adaptation to fluctuating environment and biomass production are strongly dependent on guard cell potassium channels.Proceedings of National Academy of Sciences USA,105, 5271-5276.

    [2]      Lebaudy A., Hosy E., Simonneau T., Sentenac H., Thibaud J.-B., Dreyer I. (2008) Heteromeric K⁺ channels in plants.The Plant Journal54, 1076-1082.

    [3]      Parent B., Hachez C., Redondo E.,Simonneau T., Chaumont F., Tardieu F. (2009) Drought and ABA effects on aquaporin content translate into changes in hydraulic conductivity and leaf growth rate : a trans-scale approachPlant Physiology149, 2000-2012.

    [4]      Ehlert C., Maurel C., Tardieu F.,Simonneau T.(2009) Aquaporin-mediated reductions in maize root hydraulic conductivity impacts cell turgor and leaf elongation even without changing transpiration.Plant Physiology150, 1093-1104.

    [5]      Maurel C.,Simonneau T.,Sutka M. (2010) The significance of roots as hydraulic rheostats.Journal of Experimental Botany61, 3191-3198.

    [6]      Damour G.,Simonneau T., Cochard H., Urban L. (2010) An overview of models of stomatal conductance at the leaf level.Plant Cell and Environment33, 1419-1438.

    [7]      Pantin F.,Simonneau T., Rolland G., Dauzat M., Muller B. (2011) Control of leaf expansion: a developmental switch from metabolics to hydraulics.Plant Physiology,156, 803-815.

    [8]      Vile D., Pervent M., Belluau M., Vasseur F., Bresson J., Muller B., Granier C.,Simonneau T.(2012) Arabidopsis growth under prolonged high temperature and water deficit: independent or interactive effects?Plant Cell and Environment,35, 712-718.

    [9]      Prieto J.A., Louarn G., Perez Peña J., Ojeda H., Simonneau T., Lebon E. (2012) A leaf gas-exchange model that accounts for intra-canopy variability by considering leaf nitrogen status and local acclimation to light in grapevine (Vitis viniferaL.).Plant Cell and Environment,35, 1313-1328.

   [10]     Pantin F.,Simonneau T., Muller B.(2012) Coming of leaf age: control of leaf growth by hydraulics and metabolics during ontogeny.The New Phytologist(Tansley Review)196, 369-366.

   [11]     Pantin F., Monnet F., Jannaud D., Costa J.M., Renaud J., Muller B.,Simonneau T., Genty B. (2013) The dual effect of abscisic acid on stomata.The New Phytologist197, 65-72.

   [12]     Pantin F., Renaud J., Barbier F., Vavasseur A., Le Thiec D., Rose C., Bariac T., Casson S., McLachlan D., Hetherington A.M., Muller B.,Simonneau T.(2013) Developmental Priming of Stomatal Sensitivity to Abscisic Acid by Leaf Microclimate.Current Biology23, 1805–1811.