Project properties
Title Characterization of the root hair cytoskeleton during Rhizobium infection thread formation
Group Plant Cell Biology, Laboratory of
Project type thesis
Credits 16-28
Supervisor(s) Dr. Tijs Ketelaar and Dr. Norbert de Ruijter
Examiner(s) Prof. Dr. Anne Mie Emons
Contact info Tijs.ketelaar@wur.nl Phone: 0317 482453
Begin date 2007/01/01
End date 2009/06/30
Description We want to learn about the cellular interplay between legume root hairs and Rhizobium bacteria. These two organisms can grow in isolation, but when they meet, they like to profit from each other in a symbiosis partnership. This interplay starts with root hair cell growth, gene expression, and cell division. It leads to root hair curling around bacteria, growth of plant-created infection threads containing the bacteria and plant orchestrated cell divisions, which give rise to nodules in the root cortex. Nodule formation is a desirable production of new cells. These very nodules, namely, are a comfortable home for the bacteria, well supplied with food and energy for them to live and reproduce. The bacteria pay the plant with useful nitrogen compounds. They capture nitrogen from the air and use it as the raw material for making the nitrogen-compounds that the plant needs, but cannot manufacture. Therefore, this process is very important for durable agriculture.

When Rhizobium bacteria meet legume root hairs, the root hairs first curl around the growing colony of bacteria. Next, an infection thread is formed by the plant cell. Through this infection thread, the bacteria enter the plant. How exactly this infection thread is made is not known, but our hypothesis is that it is a reversed tip growth mechanism. One of the ways to test this is to visualize the cytoskeleton of microtubules and actin filaments, ideally in living cells. To achieve this, we can use optical tweezers to place bacteria on a growing root hair to follow the infection process.

The candidate for this MSc project will characterize the cytoskeletal organization of the root hair during Rhizobium infection in living cells. Therefore, Medicago truncatula will be transformed with microtubule and actin filament reporters (TUBULIN-GFP and MAP4-GFP and FABD-GFP). We will stain actin filaments and immunolocalise microtubules since these methods provide more detail.
Used skills Transformation of Medicago truncatula with GFP-constructs; culturing of Medicago seedlings; infection of seedlings with Rhizobium bacteria; staining with fluorescent phalloidin, labeling with anti-tubulin antibody, confocal laser scanning microscopy; analysis of digital images.
Requirements PCB 30306; PPH 30306 (advised, not obliged)