Thursday 3 october 2019
Room 108 (heart school) at 2pm
(Universität Heidelberg – Centre for Organismal Studies CellNetworks, Heidelberg)
Form follows function – shaping a cell designed to invade.
Tip growth enables cells to penetrate their surrounding and thereby tap into nutrient resources, infect host organisms or find mating partners. Root hairs and pollen tubes are tip growing, single cell structures in plants that are specifically designed to invade soil and maternal tissue, respectively. We use root hairs of Arabidopsis as model to understand the architectural principles and regulatory mechanisms that drive morphogenesis of a functional cell shape. The root hair is a remarkable example of robustness and plasticity going hand in hand to ensure functional cell morphology. While root hair positioning, diameter and growth angle are robust features with little observed variation, the time window and trigger of outgrowth, growth rate and final length can be highly variable.
In this presentation, I will discuss theoretical considerations regarding the emergence of specialized cell shapes and report our recent findings on root hair formation and growth regulation. We followed the targeted recruitment of the growth machinery to the emerging site of outgrowth over time and found that polarization and growth initiation are temporally separate processes that each involve interaction of ROP GTPases with phase-specific RopGEFs. A super-resolution imaging approach revealed the formation of stable nanodomains in the polar root hair initiation domain of the plasma membrane that recruit and locally accumulate ROPs. After this robust polarization, growth regulation is influenced by environmental conditions. By allowing a single root to grow in asymmetric microfluidic environments, we could demonstrate that hair growth regulation occurs largely in a cell-autonomous fashion, likely through direct modulation of the apical growth machinery.
contact : Alexandre Martinière