Phd in GENETICS AND MOLECULAR BIOLOGY

Thesis title: Molecular mechanisms controlling the relationship between cell expansion and cell differentiation

Plant cells are enclosed by a specialized type of extracellular matrix, the cell wall. Growing cells are surrounded by the primary cell wall which is composed by three different polysaccharides: cellulose microfibrils, hemicellulose and pectins. Cellulose and hemicellulose together are fundamental to provide strength and robustness to the cell wall while pectins create a gel-like structure that allows cell expansion. Changes in the cell wall composition determine modifications of its mechanical properties. Several studies indicate that besides its structural function, the cell wall is implicated in the regulation of morphogenesis and different aspects of plant development, while a specific control on cell state remains elusive. Here, using the Arabidopsis thaliana root apical meristem as model system and by means of a molecular-genetic approach, I demonstrate that the cell wall can control and modify cells activities. I was able to show that a stiffer cell wall induces cell division while an elastic cell wall promotes cell differentiation. Moreover, by using a transcriptomic analysis, in which cell wall mechanical properties are altered in a time-controlled and in a tissue-specific manner, I laid down the foundation to shed light on the genes that, by responding to changes in cell wall mechanical properties, trigger a change in cell activity.