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From 2011.igem.org

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Module 2: Auxin Xpress

Auxin, or Indole 3-acetic acid (IAA), is a plant growth hormone which is produced by several soil bacteria. We have taken the genes encoding the IAA-producing pathway from Pseudomonas savastanoi and expressed them in Escherichia coli. Following chemotaxis towards the roots and uptake by the Phyto Route module, IAA expression will promote root growth with the aim of improving soil stability.

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Future Work

To carry on the work on the Auxin-Xpress module, there are a number of steps we would take in the immediate future and others that form part of our long term plan.

Short-term plans

1. How much auxin we are producing - hopefully we will know from HPLC.

We have carried out an HPLC assay. Preliminary results seem to indicate that our bacteria produce indole 3-acetic acid. However, we will need to conduct thorough data analysis to confirm this.

2. How much auxin we want to produce for optimal root growth - from modelling.

We will determine the optimal concentration of auxin we want our bacteria to secrete. This will help with future optimisation steps of IAA expression.

3. Construct we would build to achieve the above.

We will aim to fine-tune IAA expression in our cells.

4. Continuing the soil erosion experiment.

We will carry out the final stages of the soil erosion experiment. Hopefully we will be able to collect data before the regional Jamboree.

5. Assessing the effect of our bacterial IAA on root morphology.

We will be exposing plants to our auxin-producing bacteria for a prolonged period of time and observe changes in dry-mass, root length and root branching compared to a control that has been exposed to E. coli not producing auxin.

6. Track cell metabolic activity using Dendra

Photoconvert Dendra2 in bacterial cells that have been taken up into plant roots and image the same cells at set time intervals to assess whether the cells are metabolically active.

Long-term plans

1. Computationally model the long-term uptake and distribution pattern of IAA inside roots.

A mathematic model will be developed to quantitatively describe the relationship between root growth and the IAA concentration level inside the plant. The model will be intergrated into the IAA metabolism pathway and cell elongation process to give a more accurate prediction of the response of plants to a specific amount of IAA.

2. Testing and implementation in the field.

We have to ensure that the IAA secreted by our bacteria is beneficial for the environment and in now way detrimental to existing plants and ecosystems. For this, field trials will need to be conducted in much later stages of the project.