Team:UChile OpenBio-CeBiB/Model


Modelling Overview

Modelling commission has the objective of giving information that contributes to implementation and designing of our project through mathematical representation of the metabolic pathways involved and genetic expression kinetics. To achieve this end, the following proposals will be accomplished:

  • Elaborate a kinetic model to describe the actions of inserting FBP/SBPase regarding carbon dioxide fixation.
  • Construct a kinetic model of the ideas that we won’t be able to verify experimentally in this first approach, this is the regulation of starch synthesis pathways by the means of metE operator sensible to vitamin B12. This would allow the usage of glucose for other economical purposes, and it the preferred method is through the use of antisense RNA.
  • Get an estimation or quantify the production of certain substances that could be generated in our microalgae by this genetic circuit.
  • Carry out an economic analysis that could help evaluate the viability of the usage of this modified microalgae in bioreactors.

In the following image you can visualize the reactions involved in our system. You may notice that the Calvin Cycle is shorter than the real version, which is like 30 reactions or more (and not even in a perfect sequential circle as the one displayed). On the right side, the starch synthesis pathway is shown. Our aim is to redirect the output of glucose-6-phosphate from the Calvin Cycle in order to use it as initial material for other interesting compounds, while being able to revert this state (back to normal starch synthesis) so that our microalgae can actually survive while accomplishing the desired objective.

Genetic and metabolic pathways of our model. The Calvin Cycle evaluated is a simplified version.

Here we present the antisense technology that we want to use. The mechanism is pretty simple: Since the promoter MetE is controlled by B12 (transcription occurs only in absence of B12), if we add B12 to the culture it is possible to synthesis antisense RNA of the three enzymes (STA1, STA6 and GBS2), inhibiting the translation of these native proteins, due to the sequestration of the normal RNA by the antisense ones.

Antisense mechanism. Transgene transcription is inhibited by presence of vitamin B12. In absence of B12, the wild-type RNA is sequestrated by the corresponding antisense RNA, inhibiting starch synthesis.