Development of a light sheet microscopy system to analyse microtubule dynamics in Arabidopsis thaliana. Study of VIP3 gene function during floral development ; Développement d'un système de microscopie à feuille de lumière pour analyser la dynamique des microtubules chez Arabidopsis thaliana. Etude de la fonction du gène VIP3 au cours du développement floral

In plants, the development of aerial organs is indeterminate: it takes place throughout their lifespan. In contrast, the development of floral organs is determinate in Arabidopsis thaliana, each flower has the same number of floral organs. This difference in development is due to the maintenance or not of the pool of stem cells present in the stem cell niches, the meristems. During my thesis I showed that the transcriptional regulator VIP3 contributes to the regulation of the switch from indeterminate to determinate in flowers. This also revealed that the control of flower termination is not as robust as classically thought. Because VIP3 is also involved in the regulation of epigenetic marks and response to external mechanical stimuli, this work opens new questions on the role of mechanical signals in indeterminacy. On a more technical standpoint, the analysis of shoot development suffers from a lack of imaging methods with high temporal resolution and in-depth optical sectioning. During the last decade, light sheet microscopy has emerged as a competitive imaging modality in developmental biology. However, in plants, the technique has mainly been used in roots because of limits in the microscope design. During my thesis, I developed protocols allowing the imaging of aerial organs in A. thaliana using a novel light sheet set-up (Phaseview Alpha3) where shoot samples can be observed while in water. I set up an imaging pipeline from sample mounting to quantitative analysis, with a focus on local dynamics of microtubules in cotyledon epidermis in relation to cell shape. Altogether, this work provides both conceptual and technical prospects for future quantitative projects in plant development. ; Chez les plantes, le développement des organes aériens est indéterminé : il se déroule tout au long de leur vie. En revanche, le développement des organes floraux est déterminé chez Arabidopsis thaliana, chaque fleur possède le même nombre d'organes floraux. Cette différence de développement est due au maintien ou non du ...