Team:TU-Delft/part2
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<p>Exponential growth phase cells were put into a 96 well plate and cells are induced with alpha pheromone. Cells are mixed and OD600 signal and GFP signal (excitation 485/20, emission 590/35) is measured every 1.40 minutes.</p> | <p>Exponential growth phase cells were put into a 96 well plate and cells are induced with alpha pheromone. Cells are mixed and OD600 signal and GFP signal (excitation 485/20, emission 590/35) is measured every 1.40 minutes.</p> | ||
<h6>Outcome</h6> | <h6>Outcome</h6> | ||
- | <img src="https://static.igem.org/mediawiki/igem.org/f/f4/FUS1fluorometer.png" border="0" width=" | + | <img src="https://static.igem.org/mediawiki/igem.org/f/f4/FUS1fluorometer.png" border="0" width="80%" height="45%"><br> |
<h6>Fluorometer data of Growth (OD600) and Fluorescence intensity of <i>S. cerevisiae</i> transformed with <i>FUS1pr-EGFP</i>. A. Growth curve of alpha pheromone induced cells. B. Intensity curve of alpha induced cells. C. Intensity/Growth of alpha pheromone induced cells.</h6> | <h6>Fluorometer data of Growth (OD600) and Fluorescence intensity of <i>S. cerevisiae</i> transformed with <i>FUS1pr-EGFP</i>. A. Growth curve of alpha pheromone induced cells. B. Intensity curve of alpha induced cells. C. Intensity/Growth of alpha pheromone induced cells.</h6> | ||
<p>A GFP response is expected in yeasts transformed with <i>FUS1pr-EGFP</i> when induced with alpha pheromone. The growth curve, EGFP intensity curves and EGFP intensity divided by the growth are shown in figure. Here can be observed that during time interval t=0 until t=3 Intensity relative to growth significantly increased for concentrations of 2 μM and 20 μM. For the 200 nM the peak level is at t=2. After this, the intensity decreases to normal again. Interesting is that there can be found an almost linear correlation between GFP intensity and growth for lower concentrations (seen as lines in the lower graph).</p> | <p>A GFP response is expected in yeasts transformed with <i>FUS1pr-EGFP</i> when induced with alpha pheromone. The growth curve, EGFP intensity curves and EGFP intensity divided by the growth are shown in figure. Here can be observed that during time interval t=0 until t=3 Intensity relative to growth significantly increased for concentrations of 2 μM and 20 μM. For the 200 nM the peak level is at t=2. After this, the intensity decreases to normal again. Interesting is that there can be found an almost linear correlation between GFP intensity and growth for lower concentrations (seen as lines in the lower graph).</p> |
Revision as of 08:34, 25 October 2012
Content
IntroductionParts
Results
Conclusions
Recommendations
References
Introduction
There are two sexes of yeast cells, MATa and MATα. Whenever pheromones of the opposite sex are bound to the specific G-protein coupled receptors the MAP kinase cascade is turned on, leading to induction of mating genes such as FUS1. If a reporter gene as EGFP is coupled to the FUS1 promoter the FUS1 MAP kinase cascade can be characterized. The main questions are: What is the sensitivity of the FUS1-EGFP reporter, does the FUS1-EGFP reporter give a quantitative response, hoe long does it take before you can see a response? To answer this questions, YEGFP (Yeast Enhanced GFP) is cloned behind the FUS1 promoter and the native yeast receptors are induced by alpha pheromones. With fluorometry measurement techniques we are able to see qualitative and quantitative response in time.
Schematic overview of the FUS1-EGFP reporter
Parts
The FUS1pr-EGFP construct was designed and ordered at a synthesizing company. However the company synthesized the construct with a single nucleotide deletion in EGFP gene and therefore we cloned another EGFP behind the FUS1 promoter. The EGFP that is used is obtained from the pAG416GPD-ccdB-EGFP plasmid (kindly provided by Harmen van Rossum from Delft University of Technology). The plasmid construct was obtained by restriction and ligation in the pRSII415 expression vector. The following biobrick was created:
BBa_K775004
Results
Fluorometer experiment
Setup
Exponential growth phase cells were put into a 96 well plate and cells are induced with alpha pheromone. Cells are mixed and OD600 signal and GFP signal (excitation 485/20, emission 590/35) is measured every 1.40 minutes.
Outcome
Fluorometer data of Growth (OD600) and Fluorescence intensity of S. cerevisiae transformed with FUS1pr-EGFP. A. Growth curve of alpha pheromone induced cells. B. Intensity curve of alpha induced cells. C. Intensity/Growth of alpha pheromone induced cells.
A GFP response is expected in yeasts transformed with FUS1pr-EGFP when induced with alpha pheromone. The growth curve, EGFP intensity curves and EGFP intensity divided by the growth are shown in figure. Here can be observed that during time interval t=0 until t=3 Intensity relative to growth significantly increased for concentrations of 2 μM and 20 μM. For the 200 nM the peak level is at t=2. After this, the intensity decreases to normal again. Interesting is that there can be found an almost linear correlation between GFP intensity and growth for lower concentrations (seen as lines in the lower graph).
Flow cytometry experiment
Setup
When cells were in exponential phase they were induced with alpha pheromone. Cells where then measured with a Cytek FACScan. Graphs were analyzed with Flowjo.
Outcome
The upper part shows Side Scattering versus fluorescence intensity. Side Scattering is an indication of the morphological structure of the cells. The lower part shows a histogram of the fluorescence intensity distribution.
In the figure a signal intensity shift can be observed from the I=3*10^2 towards I=2*10^3 between the WT strain induced with alpha pheromone and the FUS1pr-EGFP strain induced with alpha pheromone (2nd and 3rd column). This indicates that yeast cells react to the alpha pheromone with a fluorescent signal. If we look at the non induced FUS1pr-EGFP strain (first column) we can see that a small region correlates with higher intensity (thus EGFP expression). This is probably the signal noise of the FUSpr1-EGFP (leakiness).Conclusions
An increase in EGFP expression can be seen when yeast cells are induced with concentrations of 200 nM 2 μM and 20 μM alpha pheromone. The peak intensity of alpha pheromone addition occurs on t=2-3 hours after induction. Further promoter leakiness can be estimated to be 4%, but this is really dependent of the type of vector used and whether plasmid or chromosomal integration is chosen.
Recommendations
Further investigation should be done on fine-tuning the promoter affinity by varying the sequence of the STE12p docking sites and experimental conditions by estimating influencing parameters during an experiment. This includes: estimating alpha pheromone degradation rate/cell.