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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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Overview

Auxin, also known as indole-3 acetic acid (IAA), is a well studied plant hormone that is responsible for plant growth in response to biotic and abiotic stresses. Usually, synthetic auxins like α-Naphthaleneacetic acid (αNAA) and 2,4-Dichlorophenoxyacetic acid (2,4-D) are used as herbicides. They have been been used effectively for the past fifty years due to their high effectiveness and cheap cost, however they are extremely stable and persist in the soil for weeks.

When altered by persistent compounds that cannot be degraded easily (such as synthetic auxins), plants are unable to keep up with the high metabolic demand correlating with over-expression of genes. Natural auxin, on the other hand, does not act as a herbicide because it is chemically labile and therefore can be easily metabolized by the plants. However, there is still a danger that too much natural auxin can be detrimental to plants and therefore was considered when designing the Auxin Xpress module. We aim to produce auxin in E. coli, as well as tightly control its expression to remain below the toxic threshold. To enable this control, we have done extensive modeling prior wet lab assembly and characterisation.