Team:USP UNIFESP-Brazil/Proof
AlgAranha Team USP_UNIFESP-Brazil
The core iGEM idea was not only to produce spider silk proteins and antibiotics. Was doing all this in microalgae!Thus, we also aimed to expand the tools and improve Chlamydomonas reinhardtii as a chassis for synthetic biology, characterizing a system for expression and secretion of recombinant proteins! We were able to transform through electroporation and successfully express a reporter protein, mCherry, in Chlamydomonas and detect its fluorescence. Our composite part, BBa_K2136010 will be of great value for any other teams working with microalgae in iGEM’s future!
Even though this organism offers exciting possibilities, as well as many other photosynthetic chassis, a limited number of parts is available for synthetic work is available in the registry. That motivated us to change this and help the growth of this part of the synbio community!
One of our goals within iGEM was to develop a “Chlamydomonas molecular toolkit”, with basic parts for everyone’s use. We had a construct, BBa_K2136010, synthesized by IDT gBlocks technology which included:
- An enhancer/promoter construct for transcription, BBa_K2136013
- A resistance gene, selection marker, against the antibiotic zeocin, BBa_K2136014
- A self cleaving peptide from foot-and-mouth disease virus, BBa_K2136017
- A signal peptide which enable secretion of the protein of interest, BBa_K2136018
This construct was already assembled through an scarless method with mCherry codon optimized coding sequence BBa_K2136016 and a Chlamydomonas terminator, BBa_K2136015
.The clones were then selected in Petri dishes containing zeocyn and screened in 96 well plates for mCherry fluorescence (excitation at 575nm, emission at 608nm) in a setup like this:
Image 0 - Setup of transformant Chlamydomonas screening
Even though the vast majority of the cells were productive, there was a variation, in great part due to the random assembly in C. reinhardtii’s genome. This, hopefully, will be surpassed with the development of new expression methods in the future (perhaps even by iGEM teams!). Here we show the expression profile during growth of the best 5 clones in our first and second screening:
Image 1 - mCherry emission/excitation in different cells in our first screen
Image 2 - mCherry emission/excitation in different cells in our second screen
The excitation/emission fluorescence spectrum of the mCherry supernatant (without cell lysis, indicating secretion) was also characterized, not only confirming the detection, but improving characterization of this protein (BBa_J06505 and BBa_K2136016 )in the context of iGEM.
Image 2 - Codon optimized mCherry spectrum of excitation and emission
Finally, we checked the hability of our system to secrete proteins through a home made filter, accordingly to our Human Practices principles. We developed a system using a 532nm green laser pointer and a red filter to probe directly our centrifuged cells. We could clearly acces the differences between the wildtype and our transformants, as follows:
![](https://static.igem.org/mediawiki/2016/2/23/T--USP_UNIFESP-Brazil--mCherry_lasersetup.png")
Image 2 - Laser and filter setup
![](https://static.igem.org/mediawiki/2016/3/39/T--USP_UNIFESP-Brazil--mCherry_superposition.png")
Image 2 - Laser, filter and mCherry spectra superposition
![](https://static.igem.org/mediawiki/2016/1/1a/T--USP_UNIFESP-Brazil--mCherry_detection.png")
Image 2 - Theoretical results of "homemade" fluorimeter
