Thesis defense: Rawen Ben Malek

To stick or not to stick? Exploring the Intercellular Spaces in Plants

Cell adhesion/separation is a mechanism not fully understood in the plant kingdom, mainly due to the technical difficulty of generating viable mutants with alterations in genes related to cell adhesion and separation processes. Focusing the study on non-essential plant organs allows us to circumvent this challenge and would enable a better understanding of the mechanism without interfering with the plant’s viability. My work aimed to characterize the process of cell adhesion and separation in the type VI glandular trichome of two tomato species. The type VI glandular trichome is a non-essential epidermal outgrowth and has a storage cavity, making it a good candidate for studying cell separation and adhesion. In type VI glandular trichomes, the cavity forms as a result of intercellular separation between the four glandular cells. Additionally, strong adhesion is observed in the upper part of the glandular cells to prevent the release of metabolites, and weaker adhesion can be observed at the attachment zone between the stalk cell and the glandular cells to allow the trichome to detach. The series of events leading to cavity formation is the result of finely regulated cell wall remodeling dynamics. My work using cytological, biochemical, and mechanical approaches has allowed me to propose a mechano-chemical model that describes the cavity as the result of buckling delamination of a growing composite material formed by two cell walls and an ‘adhesive’ material: the middle lamella. The delamination results from the constrained growth of the glandular cells, which produces a surface reaction that axially loads the cell wall material. This deformation causes a ductile fracture of the middle lamella, which could be described as cavitation.

Supervisor: Grégory Mouille - INRAE, IJPB, Versailles, équipe ACCI

Members of the jury:

> Bruce Kohorn (Rapporteur) - Bowdoin College, Brunswick, USA
> Arezki Boudaoud (Rapporteur) - Ecole Polytechnique - IP Paris
> Stephanie Drevensek (Examinatrice) - Ecole Polytechnique, IP Paris
> Atef Asnacios (Examinateur) - MSC, Université Paris Cité
> Fahmi Zairi (Examinateur) - IGCGE, Université de Lille
> Marianne Delarue (Examinatrice) - IPS2, Université Paris Saclay, Gif-sur-Yvette
> Daniel Cosgrove (Invité) – Penn State University, USA

To attend, contact Grégory Mouille

Research developed at the Institute Jean-Pierre Bourgin for Plant Sciences.