Team:Toulouse/Project/Overview

Southern France is well-known, among other things, for the gorgeousness of its landscapes. Plane trees (Platanus sp.) are widely present and participate to the charm of this area, especially along the famous “Canal du Midi”. It is impossible to imagine this UNESCO World Heritage masterpiece without its trees. Unfortunately, these trees are threatened by a severe fungal infection called canker, and today the only treatment consists in preventive tree-cutting which has a huge cost and implies significant ecological troubles.

Facing this emergency, the students from the iGEM team of Toulouse decided to be committed to the protection of their local heritage. Indeed, using a bacterium naturally present in the trees as a vector, our team offers an alternative solution originated from synthetic biology. Thanks to different genetic modules, the engineered bacterium called SubtiTree is first able to head towards the pathogen, then to bind to its cell wall in order to finally deliver different fungicides to save the tree from its invaders. Taking into account the ecological and ethical matters, the team thinks about how to limit the spreading of the optimized microorganism through different strategies. Although our project was born from a local problematic, it is transposable to other tree vascular diseases.

First, the bacterium targets the pathogen thanks to a chimiotactism module which recognizes the soluble chitin monomers (N-acetyl-glucosamine) released by the fungi.

Then, SubtiTree binds onto the pathogen by a chimeric protein anchored on one side to the bacterium pepdidoglycan and on the other side to the fungal chitin-based wall.

To finish, our designed bacterium fights against the pathogen by setting up a powerful treatment based on the production of three different fungicides.

Our team worked on different aspects to keep control on SubtiTree. The aim is to prevent horizontal transfers between different bacteria and to contain the engineered bacterium inside the tree during one season.