Abstract text: A central question in plant biology is how cells expand while maintaining the integrity of their cell walls. According to the classical Lockhart model, cell expansion is driven by turgor pressure and regulated by the extensibility of the cell wall, neglecting the role of the secretion and assembly of cell wall material in the process. 

Here we investigated the concerted oscillatory dynamics of growth, exocytosis, intracellular calcium and actin polymerization during Arabidopsis thaliana root hair growth. We compared Col0 with a mutant for Rapid Alkalinization Factor 22 (RALF22) involved in feedback signaling between the expanding cell wall and the intracellular machinery.

4D imaging (3D+t) results converge with the hypothesis that actin accumulation negatively regulates exocytosis and growth rate. Using optogenetics and microfluidic-mediated treatment aiming at perturbing exocytosis we studied rapid effects on growth and associated variables. Finally, the comparison of cell wall nanostructures in WT and ralf22 mutant cell walls, provide new insights into the role of RALF22 in the coordination of cell wall expansion.

References:
Lockhart, J. A. An analysis of irreversible plant cell elongation. Journal of Theoretical Biology. 1965.