Analysis and reconstitution of regulatory networks governing epidermal differentiation and polar root hair growth (ROOT)

Basic data for this project

Description

Tip-focused growth represents an important mechanism to establish cellular polarity and is a fundamental process that underlies the growth of neuronal axon, fungal hyphae and plant root hairs. Root hairs are cylindrical shaped cellular protuberances of specialized epidermal cells. Polar tip growth of root hairs requires tight coordination and regulation of cytoskeleton dynamics, vesicle transport and ion fluxes. In root hairs a high-tip Ca2+ gradient has been shown to be essential for polar growth. Oscillatory Ca2+ increases are superimposed on this Ca2+ gradient and are likely to coordinate oscillatory tip growth and oscillatory fluctuations of reactive oxygen species (ROS) concentrations and pH values. The long-term goal of our project is to understand the molecular components and mechanisms underlying polar RH tip growth. Moreover, we intend to reconstitute such an oscillating network. Our preliminary data as well as published findings indicate that Ca2+ activated CBL/CIPK complexes simultaneously activate NADPH oxidases, deactivate H+-ATPases and interact with GLRs suggest a central function of this Ca2+ signaling network in establishing and coordinating the processes underlying polar growth in root hairs. In this project we want to elucidate how exactly the different components of signaling network function and how they are dynamically interconnected and how quantitative changes in Ca2+ parameters govern information processing in root hairs. Consequently, this project addresses two major aims. (i) We want to explore the regulation and function of the NADPH oxidase RbohC in ROS signaling during root hair initiation and growth. (ii) We will investigate and reconstitute complete regulatory networks that underlie the oscillatory behavior of second messengers and growth in root hairs. To this end we will study the role of Ca2+ releasing glutamate receptor-like (GLR) ion channels, their regulation by CBL/CIPK complexes and will approach to reconstitute a Ca2+-release/ROS-generation circuit in a mammalian cell line. Moreover, we will investigate the role of PM H+-ATPases (that bring about pH oscillations), ROP proteins (that facilitate cellular polarity) and CDPKs (that decode Ca2+ signals) in the establishment of oscillations and polarity during root hair development. Together our investigations should reveal detailed insights of the complex interplay of these signaling components in growing root hairs.