Red, White and Grape: From Jumping Genes to Wrapping Leaves
Red or White? Even King Tutankhamun (1332-1322 B.C.) prudently stashed away amphorae of both red and white wines to enjoy in the afterlife. Biochemically, a single class of pigments found in grape skin, the anthocyanins, separates the red from white. White grapes arose from their wild, dark berried ancestors by not one, but two rare and independent genetic events: either one alone would not have given us the white grape. In fact, all ~3000 white cultivars today carry these same gene disruptions, pointing back to a common ancestor that arose millennia ago. The disrupted genes code for transcription factors, aka master regulators of biochemical pathways that can turn other genes on or off.
Science sleuths have peeked back into the gene history of Vitis vinifera to figure this out.
First, the MybA gene duplicated, giving two side-by-side copies, both active in making anthocyanins and red berries. Somewhere along the way, one of them, the MybA2 gene accumulated two mutations (depicted as stars) that rendered the resulting protein non-functional.
Independently, a “jumping gene” or retrotransposon, (green triangle) landed within the adjacent backup gene MybA1, knocking it out as well. The resulting plant, termed heterozygous, still bore red berries, because the unmutated genes on the other chromosome were active. Eventually, two heterozygous plants bred together and some offspring received both chromosomes with two nonfunctional MybA genes.
Voila, white grapes!
If you’ve ever snacked on delicious dolmas, then you know that the goodness of the grape vine goes beyond berries. Legend has it that the gods of Mount Olympus feasted on the tender leaves of the grape wrapped around morsels of rice or meat, alongside ambrosia and nectar! Although stuffed grape leaves are common around the Mediterranean, Greeks claim that dolmades were co-opted by the army of Alexander the Great to parcel out limited rations of meat during the seige of Thebes. Luckily, you only need to lay seige on your local Middle Eastern grocery store to find jarred leaves, preserved in brine. Unfurl them gently and give them a good wash to get started. It doesn’t hurt to have a glass of your favorite vintage, red or white, on hand before embarking on this project!
For the recipe on stuffed rice dolmas, visit my blog at: https://madamescientist.wordpress.com/2016/02/20/red-white-and-grape-from-jumping-genes-to-wrapping-leaves-for-dolma/
REF:White grapes arose through the mutation of two similar and adjacent regulatory genes. Walker et al., 2007 http://www.ncbi.nlm.nih.gov/pubmed/17316172
madame scientist's not-so-mad musings 
Susan Jahn should see this.
Oh, in a microsecond, Stefani Banerian
I’m still
tastingtesting the unmutated MybA genes in grape extracts.Rajini Rao are you a vegetarian? Just curious…not really relevant to the post.
Pam Adger yes I am! I was brought up vegetarian and never had meat. I joke that the only times I’ve been tempted is with venison when the deer eat up my lilies and veggies. I guess I should get a fence if I want to stay vegetarian 🙂
One of the bonuses to living in a wine grape heavy region is that I can get fresh juice from all sorts of varietals. It’s interesting to taste the breadth of flavors that are only accented through the wine making process.
I don’t think I could live without seafood..but I could give up mammal/bird just fine.
Stefani Banerian seedless fruits are one of the seven wonders of science!
Rugger Ducky I’ve never had fresh grape juice! I’ll have to look for some when I venture into wine country next.
Rajini Rao a juicer?
Rajini Rao do make sure you stop by our house for a good meal. 🙂
Pam Adger hmm, grapes are only imported from Chili etc. in the north east. No idea how fresh they are.
Oh, didn’t know you had own lab!
Grape juice is like liquid cocaine in my body. Well, if I had ever used coke. I used to drink two glasses every morning, until my barracks roommates banned me from it. Coffee is a poor substitute. I always know if my wife is thinking I need to get some yard work done, because there will be a cold container in the refrigerator.
Rugger Ducky why were they bothered by your habit of driving juice?
Sordatos Cáceres grape juice is considerably higher in fructose than virtually anything else. And the mess hall would use concentrated juice mixed with not quite enough water. Two glasses of that, and I was…always a bit too chipper. 😉
If white grapes evolved from red grapes, why are there still red grapes?
I kid…I totally kid
John DeMicco LOL…sob! I still see that argument in science communities, unfortunately.
Now, let’s talk about champagne. It happens I started studying oenology before geology. I gave up because too much biochemistry and not enough wine tasting (but it’s another story). I was studying in Reims for a National Oenology Diploma.
Champagne comes in 4 varieties (among others): the classic common one, the rosé, the blanc de blanc and the rarest blanc de noirs. I oversimplify before I get trolled.
The classic is a white sparkling wine coming from 3 varieties of grapes, pinot meunier, pinot noir and chardonnay. Actually, there were 6-7 varieties in the past but few survived the big philoxera outbreak. But this is another very interesting story, where the Americas has a huge contribution.
The first 2 varieties are red grapes. However, the flesh is white. Only the skin is coloured as Rajini Rao explained so well. Consequently, to get a white wine, you must press gently the grapes and avoid any fermentation in contact with the skins. The pressing of the grapes is a very technical job. There’s more sugar in the pulp of the berry and more acids near the skin. The first cells to give up under pressure are in the pulp, then near the skin, then the centre with the seeds very rich in tannins as the skin. So, for white, gentle pressure.
For the rosé, it’s the opposite. In some cases, rare, we leave the moût, the juice, marinate with the skins. It’s risky, it can make a wine too rich in tannins and/or too acidic like a bad bordeaux or a bad californian wine. So, often, they add red wine to it. Note that rosé champagne is mainly for north americans. It is not the best.
The last two varieties are simple: blanc de blanc is made exclusively with chardonnay, white varieties.
The blanc de noirs is made only with red grapes, one or a blend of 2. It’s slightly more yellow.
Et voilà !
Fascinating details, now I know to direct my oenology questions to you. Thanks, Olivier Malinur.
Great post!
” . . . the gods of Mount Olympus feasted on the tender leaves of the grape wrapped around morsels of rice or meat, alongside ambrosia and nectar! ”
I could live like that :=)
What do leaves and dolmas have to do with anything? I mean, they are delicious, but what are they doing in this article about color genes?
Nila Jones , they’re the mutant ninjas :=)
Nila Jones The article is about grapes and their leaves.
Also, Rajini is a brilliant cook!
Peter Lindelauf I’m relieved the segue was not jarring.
Nila Jones you have found me out 🙂
Oksana Szulhan and Nick James good saves, thank you both 😀
I do know of a study on the genetics of grape leaf morphology, but even I found it abstruse. Whereas, I could not have got through wrapping ~50 dolmas without the wine.
The idea of wrapping carbohydrates with a leaf seems universal. There is a dish, in eastern Nigeria called ekpan nkwuko, it consists of some mashed water yam wrapped in leaves of pumpkins and cooked in a sauce with blue periwinkles, palm oil, water, onions and beef.
I am not crazy about nigerian food but I eat this, occasionally, without the “crayfish” sauce (in fact fermented dry shrimps) and the periwinkles…
I wonder if it’s possible to find grape leaves not preserved with citric acid? (Citric acid preservative is not citric acid that we understand as coming from an orange… it’s manufactured…). I’d love to try to make dolmas, but react to citric acid (preservative).
I’ll look around for preservative free jars, Nico M . I’m guessing that washing off the leaves will not be good enough to get all the citrate out.
thanks Rajini! 😀
Nico M You can also pick your own, if you live somewhere that grapes grow. I do it. They are best in the spring. Later in the year, get the ones from the ends of the branches. Younger leaves can be steamed; older ones you will have to boil to make them tender.
Nila Jones, I won’t do that until you are sure the plants have not been treated by pesticides or fungicides.
Good point. I am picking leaves I grew myself, organically.
Thank you Olivier and Nila… I don’t really live in an organic area (apartment with houses nearby), and I’m also unable to forage due to disability. My parents have a grape arbor, but it’s not a chem free neighborhood either. Thank you for the kind thoughts. 🙂 Hydroponic grape leaves? 😉
Are you sure your parents put chem stuff on their grapes? They might not have any prbolems, and might just leave them alone.
Nila, vegetables coming from towns are often pretty contaminated.
Not sure grapes could grow hydroponics, it’s a small tree after all.
Olivier Malinur True. (I am a professional organic farmer, lifelong.) But, depending on where you live, food from the countryside may be as bad.
My expertise is not in hydroponics, but it seems unlikely.
Totally. The issue with food cultivated in town is, from less likely to more likely, bad water, bad air and bad soil. The issue of soil contamination is very critical, most urban soils are very improper to cultivation.
One easy way to notice it is the extinction of mole crickets. They disappeared in the 70s in my grand dad garden in Reims. Outside Reims, there were still present in some areas till the 80s.
Champagne vineyard had a very bad effect on them, they used a lot of pesticides and, as they cultivate wines on slope, the garden downhills are getting bad things.
My grand dad turned to “organic” horticulture in the late 70s. In fact, it was quite funny because there was not much change with what he was doing before.
Hi Again Nila and Olivier, my parent’s grape arbor is something decorative…their neighbor sprays her lawn and treats her pool. I’m also allergic to anything ending in -cides…so knowing what I know, I would not eat anything from there.
So, don’t.
Thanks for the #dolma recipe
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