We envision the construction of a genetic circuit that either produces ethylene or methyl-salicylate (MeSA) in response to either the presence or absence of light. In the dark state the sensor protein YF-1 first auto-phosphorylates and then phosphorylates the response regulator FixJ. Phosphorylated FixJ is then able to bind to the pFixK2 promoter thereby activating transcription of cI (the inhibitor protein) that ultimately blocks EFE production. At the same time, phosphorylated FixJ activates the transcription of Bsmt1, which initiates the synthesis of MeSA, thus slowing down fruit ripening.

In the presence of blue-light, the sensor protein YF-1 does not auto-phosphorylate and does not phosphorylate FixJ. The RNA polymerase does not recognize the pFixK2 promoter. The result is that ethylene is produced and MeSA synthesis is blocked. In other words, fruit ripening is induced.
These are our best characterized parts on the system Best natural part BBa_K1065002, 2-Oxoglutarate Oxygenase/Decarboxylase Ethylene Forming Enzyme (EFE). This part was well characterized under the control of different inducible promoters in both E. coli (NEB10beta cells) and in B. subtilis (str.168). Best engineered device
BBa_K1065310, blue light regulated amilCP producing device. This device includes an inverter cassette (composed by cI protein and pLambda promoter) that ultimately allows production of the chromoprotein amilCP only when the culture is exposed to light. Best improved part
BBa_K1065305, blue light regulated amilGFP producing device (a yellow fluorescent protein). The part BBa_K952003, extracted from the registry, was not working because it was missing the RBS between pFixK2 promoter and amilGFP coding sequence. We improved this part by mutagenesis and demonstrated that it is able to produce amilGFP in the dark. .

We also characterized the following parts:
  • BBa_K1065102: methyl-salycilate producing device.
  • BBa_K1065106: an improved version of our methyl-salycilate producing device. This device include the SAM synthetase gene to boost wintergreen production.
  • BBa_K1065311: EFE under the control of the blue light circuit with inverter. This device produces ethylene upon photoinduction.
  • BBa_K1065309: EFE under the control of the blue light circuit without inverter. This device successfully produced ethylene in the dark.
Check how we exploited our parts to ripen fruit!
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