Mechanical regulation of tissue flatness in Marchantia
The production of flat organs involves a tight regulation of tissue expansion. During growth, the cell wall is under mechanical tension and continuous remodelling, requiring mechanisms to sense and maintain cell wall integrity (CWI). Here we studied the link between CWI sensing and flatness of Marchantia polymorpha thalli. We considered FERONIA (FER), a CWI sensor, and assessed its role in the maintenance of thallus shape. We developed a pipeline to quantify flatness at multiple scales. We found that both abolishing and increasing FER expression leads to loss of flatness. Based on experiments that reduce cell wall tension and partially restore wild-type cell size and thallus morphology, we ascribe loss of flatness to under- or to over-reaction of plants to mechanical stress. Altogether, our results support the concept that responses to mechanical stress contribute to the robustness of morphogenesis