Growth and Development of higher plants

The root plays a major role in mineral nutrient and water acquisition. It is also the first organ to undergo abiotic stress caused by either pollutants or deficit of nutrients. These various stresses as well as pH, osmotic and drought stress might have tremendous effects on the root architecture although the molecular links are still poorly deciphered. More particularly, transporters involved in water and nutrient transport have been identified at the molecular level. However, how they intervene in the root development, how they are regulated and how they respond to abiotic stress is still largely unknown. This work package is dedicated to a better molecular identification of the relationship between root development, nutrition and abiotic stress. Among the different mechanisms underlying adaptation to metal toxicity/nutrient deficiency, a focus will be made on transport processes (at the cellular level and between root and shoot) and their regulation. Some partners have already characterized at the gene and protein level several key transporters active in root tissues. They belong to three transporter families:  P-type ATPases (P3, P4A), aquaporins (P4B) and ATP Binding Cassette (ABC) transporters (P4A). We will therefore build on this knowledge to address the regulation and function of these transporters in relationship with root development. While the project proceeds, other transporters identified in this or other work packages will be integrated in this analysis.
This WP will benefit from proteomics approaches (P4) for the identification of root proteins that are differentially expressed or post-translationally modified upon stress. In addition, P1 will provide FACS facilities to study cell-type specific responses to stress. Of particular significance here are the specific responses in the epidermal tissue in direct contact with the soil and the vascular tissues, which mediate the communications between the root and the shoot. In addition, as a tool to investigate the kinetics of root-shoot communication in stress, P1D will offer a robotized imaging platform for real time follow-up of the effect of stress applied to the roots, on the key physiological parameters in the shoot tissue, i.e. photosynthesis and transpiration. P1D has established a unique lab-scale robotized setup with combined thermography, chlorophyll fluorescence imaging and video imaging. Procedures for time-lapse photography and automated generation of movies for rapid visualisation of changes, as well as for automatic quantification of leaf surface temperature and chlorophyll fluorescence intensity are available.
How particular stress conditions will interfere with cell division will be studied in collaboration with P1 and cell expansion with P5. Firstly kinematic analyses performed in collaboration with P1C will enable to pinpoint the contribution of cell cycle and cell expansion parameters in the growth response to the stress. In collaboration with P1A the effect on lateral root initiation and root architecture will be charted. For further characterization of cell cycle effects P1B can contribute by analysing cell cycle gene activities by means of a collection of cell cycle promoter GUS lines that have been generated in his group. Differences in cell expansion parameters can be further characterized using extron measurements and FESEM technology in the lab of P5.

Particular transporters or stress conditions will be studied as follows.