Transgene Design

Grace Troupe, Presenter Author

10/11/2018 Added

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This video will help you get more practice thinking like a transgene designer. You must pick the right coding region and promoter to meet your goals for your end product.

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[00:00:03.220]Now that you have begun to think
[00:00:04.540]about how changing the promoter region of a gene
[00:00:07.590]also changes where the gene is turned on,
[00:00:10.460]we're going to get a little bit of practice
[00:00:12.430]of this type of thinking by designing our own transgenes.
[00:00:16.050]This animation follows some stories of real transgenes
[00:00:19.120]that have been on the market.
[00:00:21.160]So let's get started.
[00:00:24.430]Your assignment is to design a transgene for a corn plant
[00:00:27.670]that will allow the plant to kill European cornborer larvae
[00:00:31.740]only when they feed on plant's green tissue.
[00:00:35.530]Use the correct combination of promoter and coding regions
[00:00:38.472]from the following genes.
[00:00:42.550]Gene number one.
[00:00:44.270]It's cloned from cauliflower mosaic virus.
[00:00:47.320]This gene is expressed in all plant tissues
[00:00:50.250]and encodes the 35S ribosome that the virus needs
[00:00:54.210]to replicate in plant tissues.
[00:00:57.370]Next up is gene number two.
[00:00:59.470]This was cloned from bacillus Thuringiensis bacteria
[00:01:03.380]and encodes a protein that the bacteria uses
[00:01:06.030]to kill some caterpillars such as European cornborer larvae.
[00:01:11.750]Finally, gene number three.
[00:01:13.530]This was cloned from a corn plant.
[00:01:15.620]The gene encodes a protein the plant needs
[00:01:18.090]for photosynthesis and the gene is only expressed
[00:01:21.160]in green tissue that has active photosynthesis.
[00:01:25.660]All right, so now let's think about our goal one more time.
[00:01:28.500]We want the ability to target cornborers
[00:01:31.640]that feed on green tissue.
[00:01:34.800]Well, if I look here, I know that I want
[00:01:38.330]the protein product to be toxic to cornborer.
[00:01:42.710]So I'm gonna try this coding region.
[00:01:48.430]Looks good, so this coding region is what goes
[00:01:51.680]to actually make the protein and it makes a toxin
[00:01:54.460]that's specific to the larvae.
[00:01:57.520]So, now we need to pick a promoter.
[00:02:01.810]All right, so let's just try putting the whole gene in.
[00:02:07.710]Oh, that didn't work.
[00:02:09.160]Hm, well, that is probably because the promoter
[00:02:13.690]from the bacteria isn't recognized by the plant
[00:02:16.280]to be expressed in the areas that we want.
[00:02:19.030]All right, so let's try this one.
[00:02:20.450]It says it's non-specific.
[00:02:23.480]Ah, so what non-specific must mean is that
[00:02:26.864]it doesn't discriminate amongst step cells.
[00:02:31.720]So this would cause the gene to be expressed
[00:02:34.090]in every tissue, not just the green tissue.
[00:02:37.440]So let's try the last option.
[00:02:42.440]Ah, this worked!
[00:02:44.290]So we borrowed this promoter from a gene
[00:02:46.410]that's normally expressed in all
[00:02:49.330]of a corn plant's green tissue.
[00:02:52.050]So this meets our goals.
[00:02:56.460]So this is a real transgenic event called 176,
[00:03:01.990]but it could only protect corn plants
[00:03:03.830]in actively photosynthesizing green tissue.
[00:03:07.310]This meant that they are still susceptible
[00:03:09.713]later in the season when they start turning brown,
[00:03:12.920]or even in tissue that isn't green,
[00:03:15.290]like the roots, the silks, or the ears.
[00:03:18.900]So this is how scientists knew that
[00:03:21.120]they hadn't quite chosen the perfect promoter.
[00:03:23.960]So they wanted to make another version,
[00:03:25.840]which is our next task.
[00:03:29.260]So now your assignment is to design a transgene
[00:03:32.110]for a corn plant that will allow the plant
[00:03:33.870]to kill European cornborer larvae
[00:03:36.451]when they feed on any tissue of the plant.
[00:03:40.030]Use the correct combination of promoter and coding regions
[00:03:43.230]from the following genes.
[00:03:45.210]All right, so we have the same three gene options,
[00:03:51.610]and we still want to target cornborer.
[00:03:54.210]So we'll pick the same coding region,
[00:03:59.550]and now we need to pick a promoter.
[00:04:07.070]So we learned last time that the third option
[00:04:10.150]only puts the gene, makes it expressed in green tissues.
[00:04:14.890]And what if we just put the whole gene in?
[00:04:17.200]Maybe that will work this time from bacteria.
[00:04:20.570]No, it's, the corn plant still won't recognize
[00:04:24.401]the promoter from the bacteria.
[00:04:27.260]So let's try this option from the virus.
[00:04:32.550]Perfect.
[00:04:33.383]Since it's a non-specific promoter,
[00:04:35.600]it'll be expressed in every single tissue.
[00:04:38.780]So now we have a viral promoter
[00:04:41.123]and we have a bacterial coding region.
[00:04:44.680]Does this mean that we're putting viruses
[00:04:46.390]and bacteria into our corn?
[00:04:49.040]No, what we actually do is we just take
[00:04:51.360]these small fragments of DNA,
[00:04:53.680]and when we put it into the corn plant,
[00:04:56.300]the corn will treat it as one of its own genes,
[00:04:59.240]and this works because the DNA code is universal.
[00:05:05.610]So now you have a little bit more practice
[00:05:07.620]thinking like a transgene designer.

Transgene Design

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Transgene Design

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