Presentation
 
Since 2009, I have been leading the 'Environmental Stresses and Integrated Growth Control Processes' team at the Laboratory of Plant Ecophysiology under Environmental Stresses (UMR LEPSE), which includes 3 researchers, 2 research technicians, 1 assistant engineer, 3 PhD students, 1 post-doctoral student, as many pre-doctoral students and temporary staff to support the experiments. The general objective of my research work was to identify and prioritise the processes controlling the response of leaf development to different environmental stresses. I assessed the contribution of cellular variables, such as cell division, cell expansion and endoreplication processes to the plasticity of leaf development. This project was carried out in the context of genotype x environment interaction analyses.

To carry out this project, I participated in the development of the PHENOPSIS phenotyping platform, for which I have been scientific manager since its creation in 2003. Since 2011, PHENOPSIS has been part of Montpellier Plant Phenotyping Platforms (M3P), a structure that groups together the three phenotyping facilities of LEPSE: PHENOPSIS, PHENODYN and PHENOARCH.

Recent results

In recent years, numerous contracts have enabled me to establish close collaborations with experts in quantitative genetics and molecular biology in the model plant Arabidopsis thaliana. Together, we have analysed the relationship between leaf growth and the environment using multi-disciplinary approaches and have shown the interest that dynamic and/or multi-scale analysis of leaf growth could have for QTL analyses, and for the analysis of the expression of large quantities of genes and the presence of proteins in leaves. All the results obtained by dissecting the 'leaf area of rosette' phenotype into a large number of underlying variables (from transcript to leaf area) over time, in a large number of genotypes, and under a variety of environmental conditions have revealed emergent properties of leaf development.
I will highlight here some important messages from this work:

(1)   The rosette consists of successive leaves with different morphological and dynamic characteristics. Statistical segmentation models have made it possible to identify successive developmental phases and to group together leaves with identical characteristics. The length of these phases varies according to the genotypes (Lièvre et al., 2016).

(2)   Some of the phenotypes observed at the leaf level at a given rank, or at the epidermal cell level of the same leaf, or at the level of transcripts and proteins of the same leaf, are explained by the total number of leaves in the rosette and/or the flowering date. This should be taken into account when comparing genotypes with different numbers of leaves (Lièvre et al., 2013; Massonnet et al., 2015).

(3)   The expansion of the rosette and/or individual leaves of the rosette is a dynamic process that can exhibit a compensation phenomenon: when the initial expansion is rapid, a shorter expansion time is observed under many conditions (genetic background, water stress, photoperiod...) (Lièvre et al., 2013; Bac-Molenaar et al., 2015 & 2016). This has an important impact for the detection of leaf expansion QTLs or the comparison of molecular signatures of growth at a given date or stage of expansion (Baerenfaller et al., 2012).

(4)   The leaf has its own control of expansion and, to some extent, controls the underlying cellular processes. This hypothesis has often been discussed in the literature, questioning a purely cellular control of expansion. Similarly, the level of endoreplication in the leaf would depend on the expansion of the leaf itself (Tisné et al., 2008; Tisné, Barbier & Granier, 2011; Massonnet et al., 2011) .

 Research project

Arabidopsis thaliana s a very interesting model species to have access to all the tools mentioned above and allowed me to progress rapidly in my research project. Multi-scale phenotyping of single, double and triple mutants with contrasting baseline levels of cell division or endoreplication in the leaves and under different soil water stresses has provided insight into the role of these processes in leaf growth and plasticity (ANR project CKI-Stress, ongoing). This type of germplasm is increasingly being applied to other species of agronomic interest. Over the past 4 years, my project has taken a certain turn. Indeed, I have assessed the extent to which the results found on this model plant are transferable to cultivated species such as rapeseed in the AgWaterBreed project (ClimateKic, FP7) and tomato in an Agropolis project.

Since September 2017, I am in a mobility process to carry out a new project in another research unit.

Selection of recent publications :

Lièvre M., Granier C. & Guédon Y. (2016) Identifying developmental phases in Arabidopsis thaliana rosette using integrative segmentation models. New Phytologist. 210, 1466-1478

Bac-Molenaar J.A., Vreugdenhil D., Granier C. & Keurentjes J.J.B. (2015) Genome wide association mapping of growth dynamics detects time-specific and general QTLs. Journal of Experimental Botany. 66 (18) 5567-5580.

Vasseur F., Bontpart T., Dauzat M., Granier C. & Vile D. (2014) Multivariate genetic analysis of plant responses to water deficit and high temperature revealed contrasted adaptive strategies. Journal of Experimental Botany. 65 (22) 6457-6469.

 Lièvre M., Wuyts N., Cookson S.J., Bresson J., Dapp M., Vasseur F., Massonnet C., Tisne S., Bettembourg M., Balsera C., Bédiée A., Bouvery F., Dauzat M., Rolland G., Vile D. & Granier C. (2013) Phenotyping the kinematics of leaf development in flowering plants: recommendations and pitfalls. WIREs Developmental Biology 2: 809-821.

Baerenfaller K., Massonnet C., Walsh S., Baginsky S., Bühlmann P., Hennig L., Hirsch-Hoffmann M., Howell K. A., Kahlau S., Radziejwoski A., Russenberger D., Rutishauser D., Small I., Stekhoven D., Sulpice R., Svozil J., Wuyts N., Stitt M., Hilson P., Granier C. & Wilhelm G.  (2012) Systems-based analysis of Arabidopsis leaf growth reveals adaptation to water deficit. Molecular Systems Biology 8: 606.

Recent or ongoing projects / main collaborators

ARABRAS, ERAPG [2006-2010] / Max Plank Institute - Koln (M. Koornneef)

3D Leaf, Agropolis [2007-2011] / DAP-Montpellier (E. Costes) , Virtual Plant-Montpellier (Y. Guédon)

AGRONOMICS, FP6 Europe [2007-2012] /Max Plank Institute-Golm (M. Stitt) and Tübingen (D. Weigel), Gent University (L. de Veylder), ETH Zurich (W. Gruissem)

Drought Natural Variation, ANR [2007-2011] / SGAP -Versailles (O. Loudet)

AgWaterBreed, FP7 Climate Kic [2011-2015] / Juelich Plant Phenotyping Center (F. Fiorani, R. Pieruschka), Bayer Crop Science

European Plant Phenotyping Platform, EPPN [2012-2015] / Juelich Plant Phenotyping Center (R. Pieruschka)

CKI-Stress, ANR [2013-2017] / IBMP Strasbourg (P. Genschik)

Tomates, Agropolis [2015-2018] / Virtual Plant Montpellier (Y. Guédon), BFP Bordeaux (C. Chevalier, J.P. Renaudin, C. Cheniclet), PSH Avignon (N. Bertin, V. Baldazzi),