La conductivité hydraulique racinaire (Lpr) traduit la facilité du passage de l'eau au travers des racines. Ce paramètre, majoritairement contrôlé par l'activité de canaux hydriques membranaires (aquaporines), est modulable par diverses contraintes environnementales. Ce travail a permis de caractériser, sur un même organisme (Arabidopsis), les effets d'un ensemble de contraintes abiotiques et biotiques, représentatives de situations environnementales, sur la Lpr. Alors que la flagelline n'affecte pas la Lpr, les contraintes osmotiques (NaCl, mannitol), oxydantes (H2O2, NO) et nutritionnelles (carence en phosphate, en nitrate, culture des plantes en nuit prolongée) inhibent la Lpr. Par contre, la réalimentation en phosphate ainsi que l'addition de saccharose à des plantes cultivées en nuit prolongée stimulent la Lpr. Une approche phosphoprotéomique quantitative, basée sur l'analyse par MS de protéines microsomales racinaires purifiées à partir de plantes cultivées dans trois de ces contextes (NaCl, NO, phosphate) a permis de quantifier les variations d'abondance de l'ensemble des aquaporines racinaires ainsi que de leur état de MPT. D'un point de vue qualitatif, 22 aquaporines ont été identifiées dans la racine ainsi que plusieurs types de MPTs, incluant des nouveaux sites de phosphorylation (7), de méthylation (13 à 15), de formylation (4) et de déamidation (25 à 26). D'un point de vue quantitatif, cette étude a permis de conclure que les observations réalisées au niveau de la Lpr sont la résultante de mécanismes multifactoriels incluant l'état de phosphorylation des trois sites de l'extrémité C terminale de PIP2;1/2;2/2;3, l'état de phosphorylation de l'extrémité N terminale de PIP1;1/1;2, ainsi que les aquaporines TIPs. Ce travail permet donc de proposer de nouveaux mécanismes moléculaires impliqués dans la régulation de la Lpr en réponse à des contraintes de l'environnement / The water uptake capacity of plant roots (root hydraulic conductivity, Lpr) is mainly determined by water channels (aquaporins) and is modulated by environmental constraints. The present work characterised, in a unique organism (Arabidopsis), effects on Lpr of abiotic and biotic constraints representative of environmental situations. Whereas flagelline does not affect Lpr, osmotic (NaCl or mannitol), oxidative (H2O2 or NO) and nutritional (phosphate or nitrate starvation, prolonged night) stimuli inhibit Lpr. However, phosphate and sucrose resupply stimulate Lpr. A phosphoproteomics approach based on MS analysis of microsomal proteins extracted from roots of plants cultivated in different environmental constraints (NaCl, NO,phosphate starvation and resupply) allowed to quantify variations of abundance of roots aquaporins and of their PTMs. As a qualitative point of view, 22 aquaporins were identified in roots as well as several post-translational modifications including new sites of phosphorylation (7), methylation (13 to 15), formylation (4) and deamidation (25 to 26). From a quantitative point of view, the present work drove to the conclusion that the modulations of Lpr result from multifactorial mechanisms including the phosphorylation status of the C terminal part of PIP2;1/2;2/2;3 and of the N-terminal part of PIP1;1/1;2 and TIP aquaporins. This study proposes new molecular mechanisms implicated in Lpr regulation in response to various environmental situations.

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Introduction: Chronic myeloid leukaemia is a blood cancer which progresses from a chronic phase to an acute blast crisis if untreated. Disease progression and treatment resistance may be precipitated by the mutator action of BCR/ABL protein tyrosine kinase (PTK), but only few protein phosphosites involved in the DNA damage response have been investigated with respect to BCR/ABL action. Aim: The aim of this PhD project was to demonstrate that BCR/ABL PTK expression can affect the response to genotoxic stress signalling at the protein phosphorylation level. Methodology: Etoposide-induced DNA damage response has been studied in control and BCR/ABL PTK-expressing Ba/F3 cells using apoptosis and γH2AX assays. Quantitative phosphoproteomics was performed with iTRAQ peptide labelling to discover putative modulated phosphorylation sites. Absolute quantification (AQUA ) performed with selected reaction monitoring was used to validate discovery phosphoproteomics. The effect of genotoxic stress on the THO complex protein Thoc5/Fmip was studied using western blots. Results: The expression of BCR/ABL PTK induced γH2AX phosphorylation after etoposide exposure. This was associated with the modulation of H2AX tyrosine 142 phosphorylation, MDC1 (serines 595 and 1053) and Hemogen serine 380 phosphorylation among proteins regulated by both BCR/ABL PTK and etoposide. We identified that leukaemogenic PTKs mediate Thoc5/Fmip phosphorylation on tyrosine 225 via Src proto-oncogene and oxidative stress, while ATM and MEK1/2 may control its phosphorylation. Human CD34+ CD38- leukaemic stem cells showed pronounced level of THOC5/FMIP tyrosine phosphorylation. Expression of phosphomutant Thoc5/Fmip Y225F might reduce apoptosis mediated by etoposide and H2O2. Conclusion: BCR/ABL PTK can sustain, create, block and change the intensity of protein phosphorylation related to genotoxic stress. Modulation of H2AX, MDC1, Hemogen and Thoc5/Fmip post-translational modifications by BCR/ABL PTK might promote unfaithful DNA repair, genomic instability, anti-apoptotic signalling or abnormal cell differentiation, resulting in leukaemia progression.