Magali di Pietro

(Doctorante B&PMP- Equipe Aquaporines)

Phosphorylation of aquaporins and response of Arabidopsis thaliana roots to abiotic and nutritional stresses

The uptake of water by roots is a key function for maintaining the plant water status. The root hydraulic conductivity, Lpr, that describes the ability of water to cross the roots, can be regulated by environmental conditions. At a molecular level, Lpr is mediated in large part by water channel proteins named aquaporins.
Using the pressure chamber technique, the regulation of Arabidopsis Lpr by a representative panel of environmental conditions: osmotic (NaCl and mannitol), oxidative (H2O2 and NO), nutritional (phosphate, nitrate, sucrose) and biotic (flagelin) treatments, was analysed. These results have provided the context for a quantitative (phospho-) proteomics study of aquaporins in plants under environmental stresses. For this, microsomal extracts were obtained for each condition and proteins were identified and quantified by mass spectrometry, in collaboration with the LPF. As a qualitative point of view 22 of the known 35 aquaporins isoforms and 7 new phosphosites were identified. Quantitative data presently available for 3 of the treatments revealed a regulation of the phosphorylation of the C-terminal tail of several PIP2s. It was also found that in response to a NaCl and NO treatment, TIP2;3 and TIP2;2 can be regulated, respectively.
My objectives are 1) to complete the quantitative (phospho-) proteomics of aquaporins for the entire set of stresses which will provide the first overview of the phospho-regulation of root aquaporins under stress; 2) to focus on the role of TIP2;3 in the root water transport and the biochemical events involved in response to the NaCl treatment.