The progression of the Poplar root in response to mechanical stresses exerted by the soil

Presentation of the subject (context, problematic, envisaged methodology):

The proposed project focuses on the study of the impact of soil impedance on root growth plasticity and is integrated into the research activities, carried out by the MECA team of the UMR PIAF. This research topic started in September 2015, in the framework of a thesis and follows a project currently underway in the framework of the Emergence Program of the i-site-Clermont CAP2025 project. 
The heterogeneity of the soil caused by its texture, its structure and amplified by drought or / and compaction exert a mechanical resistance on the roots of plants. The latter establishes mechanisms that allow them to avoid or cross the barriers. However, we know very little about how roots perceive and integrate mechanical forces at the cellular and molecular level. 

By its position at the root tip, the cap is considered a zone of perception and integration of edaphic factors. Recently, a mammalian ortholog of Piezo, named PIEZO1, has been identified in Arabidopsis thaliana and is expressed in root cap cells. The data suggest that PIEZO1 plays an important role in root mechanotransduction as a mechanosensitive ion channel. We have PIEZO1 RNAi poplar lines available in the laboratory. During this internship, we propose to analyze the behavior of poplar adventitious roots of mutated lines.
Methods considered: Poplar cuttings will be arranged in an in vitro culture system of variable rigidity, which is able to mimic changes in mechanical stress (Roué et al., 2020). Information on adventitious root tip shape, root size, angle of progression will be collected. This work will be carried out in close collaboration with M-M Bogeat-Triboulot (UMR INRAE/UL SILVA, Nancy). 
In order to approach the understanding of the underlying cellular mechanisms, several lines of study will be proposed. For example, we propose to analyze the deformation capacity of root apex cells from images obtained with a light sheet microscope (SPIM for Selective Plane Illumination Microscopy), available in the laboratory. In a first step, observations and analyses will be performed with young Arabidopsis thaliana germinations (GFP lines). 
The internship will thus combine image analysis, microscopy and mechanical tools. We propose to carry out an interdisciplinary approach by associating physical approaches with those of biology.

Contact :

Valerie.Legue@uca.fr