Deciphering the plasma membrane associated responses to mechanicla stress
Plants use their mechanical environment as a signal to trigger molecular responses such as rearrangements in microtubule (MT) dynamics that drive cell wall modifications. But how mechanical stress is perceived and transduced is still poorly understood and remains a challenging question in both animals and plants. Among the structural components of plant cells the plasma membrane has received very little attention. Yet its position at the interface between the cell wall and the cortical MT arrays makes it a key factor at the nexus between biochemical and mechanical signal.
Figure 1. Mechano-sensing and cMT dynamics in Arabidopsis. (adapted from Ackermann and Stanislas 2020). On the left side, mechano-sensitive channel opening and PIN1 polarisation in response to mechanical stress. At the top, parallel cMTs alignment to the mechanical stress and polar deposition of cellulose fibres parallel to the cMT arrays. On the right side, trafficking of CESA and pectin exocytosis allow cell wall modification. At the bottom, molecular mechanisms that induce cMTs reorganisation
We aim to elucidate how mechanical signal trigger microtubule reorganisation and drive cell wall deposition. The current limitations in the plant field are a) the possiblity to induce a controlled and quantifiable mechanical stress, 2) to determine and interpret the mechanical stress pattern, and 3) to visualise that mechanical force serves as direct signal to activate specific downstream pathways. To overcome these limitations, we will use living plant cells lacking cell walls, so called protoplasts, and use a microfluidic device we developed recently to trap them individually and induce mechanical stimuli, tightly controlled by the flow rate and coupled with high resolution microscopy. As a proof of concept, we already produced such a prototypical microfluidic device and succeeded in immobilizing protoplasts and inducing mechanical stress.
Analysis of molecular responses triggered by mechanical stress will allow to clearly link molecular responses and mechanical stress and will give a better understanding of the first steps of mechano-sensing signalling and responses.