REFAHI , Yassin

In this dissertation we are interested in how shoot structure emerges from the functioning of their apical meristem. For this, we investigate the structure of Arabidopsis thaliana shoot apical meristem at different scales. The thesis starts by studying at macroscopic scale plants in which the regularity of phyllotaxis has been perturbed and...

Vascular plants produce new organs at the tip of the stem in a very organized fashion. This patterning process occurs in small groups of stem cells, the so-called shoot apical meristems (SAM), and generates regular patterns called phyllotaxis. The phyllotaxis of the model plant Arabidopsis thaliana follows a Fibonacci spiral, the most frequent...

Phyllotaxis is the geometric arrangement of organs in plants, and is known to be highly regular. However, experimental data (from [i]Arabidopsis thaliana[/i]) show that this regularity is in fact subject to specific patterns of permutations. In this paper we introduce a model for these patterns, as well as algorithms designed to identify these...

Phyllotaxis is the geometric arrangement of organs in plants, and is known to be highly regular. However, experimental data (from Arabidopsis thaliana) show that this regularity is in fact subject to specific patterns of permutations. In this paper we introduce a model for these patterns, as well as algorithms designed to identify these...

Abstract In vascular plants, the arrangement of organs around the stem generates geometric patterns called phyllotaxis. In the model plant, Arabidopsis thaliana, as in the majority of species, single organs are initiated successively at a divergence angle from the previous organ close to the canonical angle of 137.5°, producing a Fibonacci...

The shoot apical meristem (SAM) is at the origin of all the plant above-ground organs (including stems, leaves and flowers) and is a biological object of interest for the understanding of plant morphogenesis. The quantification of tissue growth at a cellular level requires the analysis of 3D microscopic image sequences of developing meristems....

Exploration of developmental mechanisms classically relies on analysis of pattern regularities. Whether disorders induced by biological noise may carry information on building principles of developmental systems is an important debated question. Here, we addressed theoretically this question using phyllotaxis, the geometric arrangement of plant...

Converting plant cell walls, as a renewable source of energy and materials, into bioproducts is an important step toward reducing dependence on fossil fuels. The primary obstacle in this conversion is overcoming the cell wall's inherent resistance to enzymatic breakdown called recalcitrance. Much of the research during past decades has...

Achieving an economically viable transformation of plant cell walls into bioproducts requires a comprehensive understanding of enzymatic deconstruction. Microscale quantitative analysis offers a relevant approach to enhance our understanding of cell wall hydrolysis, but becomes challenging under high deconstruction conditions. This study...

We have analyzed the link between the gene regulation and growth during the early stages of flower development in Arabidopsis. Starting from time-lapse images, we generated a 4D atlas of early flower development, including cell lineage, cellular growth rates, and the expression patterns of regulatory genes. This information was introduced in...

How biological systems generate reproducible patterns with high precision is a central question in science. The shoot apical meristem (SAM), a specialized tissue producing plant aerial organs, is a developmental systemof choice to address this question. Organs are periodically initiated at the SAM at specific spatial positions and this...