Tomatoes!

By Razib Khan | June 28, 2012 11:19 pm

This story in The New York Times, Flavor Is Price of Scarlet Hue of Tomatoes, Study Finds, is pretty cool:

Yes, they are often picked green and shipped long distances. Often they are refrigerated, which destroys their flavor and texture. But now researchers have discovered a genetic reason that diminishes a tomato’s flavor even if the fruit is picked ripe and coddled.

The unexpected culprit is a gene mutation that occurred by chance and that was discovered by tomato breeders. It was deliberately bred into almost all tomatoes because it conferred an advantage: It made them a uniform luscious scarlet when ripe.

Now, in a paper published in the journal Science, researchers report that the very gene that was inactivated by that mutation plays an important role in producing the sugar and aromas that are the essence of a fragrant, flavorful tomato. And these findings provide a road map for plant breeders to make better-tasting, evenly red tomatoes.

The paper, Uniform ripening Encodes a Golden 2-like Transcription Factor Regulating Tomato Fruit Chloroplast Development:

Modern tomato (Solanum lycopersicum) varieties are bred for uniform ripening (u) light green fruit phenotypes to facilitate harvests of evenly ripened fruit. U encodes a Golden 2-like (GLK) transcription factor, SlGLK2, which determines chlorophyll accumulation and distribution in developing fruit. In tomato, two GLKs—SlGLK1 and SlGLK2—are expressed in leaves, but only SlGLK2 is expressed in fruit. Expressing GLKs increased the chlorophyll content of fruit, whereas SlGLK2 suppression recapitulated the u mutant phenotype. GLK overexpression enhanced fruit photosynthesis gene expression and chloroplast development, leading to elevated carbohydrates and carotenoids in ripe fruit. SlGLK2 influences photosynthesis in developing fruit, contributing to mature fruit characteristics and suggesting that selection of u inadvertently compromised ripe fruit quality in exchange for desirable production traits.

Genetics for better living! But I had no idea that the laws in regards to mutant varieties were so retrograde:

But were the genetically engineered tomatoes more flavorful? Because Department of Agriculture regulations forbid the consumption of experimental produce, no one tasted them.

And, Dr. Giovannoni says, do not look for those genetically engineered tomatoes at the grocery store. Producers would not dare to make such a tomato for fear that consumers would reject it.

But, Dr. Powell said, there is a way around the issue. Heirloom tomatoes and many wild species do not have the uniform ripening mutation. “The idea is to get the vegetable seed industry interested,” Dr. Powell said.

Image credit: Fir0002/Flagstaffotos, GFDL v1.2.

CATEGORIZED UNDER: Anthroplogy, Genetics
  • Justin Giancola

    Yes! That’s what I’m dying for: better tasting tomatoes. Tomato 2.o ;p

  • mdb

    Interesting, I went to a tomato tasting festival last summer and of all the varieties I tasted the reds were my least favorite – most were just bland. There was a mottled black one that was phenomenal (I have the name written down somewhere). That was a heirloom variety as were all the other ones I liked as well. This helps explains the popularity and price of the heirlooms. Every grocery store I go to has has heirlooms (still haven’t found that mottled black one though), so I think people are interested – production just has to catch up.

  • Sandgroper

    The link to the paper doesn’t work for me.

    No biggie, the link in the NY Times story works, but I’m just saying.

  • Eurologist

    The same is true for many other commercially selected and grown fruit and vegetable varieties. Selection for (even) color, hard skin, good transport qualities, resistance to diseases by cross-breeding bland wild varieties etc. commonly leads to inferior products.

    Strawberries are a good example – but there are many others:
    http://www.bbc.co.uk/blogs/food/2012/05/do-strawberries-taste-as-good.shtml
    Research has shown that wild varieties contain a lot more different flavor agents, and a higher concentration of them.

    I grow a lot of (heirloom or non-commercial) herbs, fruits, and vegetables myself, and the difference can be mind-boggling (e.g., tomatoes, blueberries, mandarins, carrots, cherries, etc.). In addition to the above, using little and low-N fertilizers leads to fruits and vegetables that are much more “concentrated”, with lower water content, and a much longer room-temperature shelf life in my home after ripening.

    But yes, I am certain there are many complex links between these genetic expressions, and selecting for transport properties and an even coloration should not be done without monitoring other important qualities and according back-cross-breeding to capture those.

  • Dm

    The story I recall is different, that “flavorful” engineered tomatoes had an additional suppressed gene to delay softening and decay of the flesh, and therefore they were OK to be harvested later, thus more than compensating for the lost flavor. The no-decay tomatoes were marketed in California for one season, but then the developer company has been acquired and the new owners shifted production to Mexico, where production crashed. Apparently too hot a summer was really bad for the cultivar. And the new, bigger company wasn’t really that interested in this product in the first place, so they let the “flavor champion” project die.

  • I_Affe

    Eurologist,

    “using little and low-N fertilizers leads to fruits and vegetables that are much more “concentrated”, with lower water content, and a much longer room-temperature shelf life in my home after ripening.”

    Can you say more on this? Is this from your own garden or published results?

  • pconroy

    @Eurologist,

    Right. I grew up in Ireland and can say that I’ve never tasted Tomatoes or Strawberries in the USA that were as tasty s those in Ireland.

    My wife raves about “New Jersey Tomatoes”, but when I saw the large, bulging tomatoes she was referring to, I said they looked like “Beef Tomatoes”

    http://en.wikipedia.org/wiki/Beefsteak_(tomato)

    Sure enough, when I had some, that’s exactly what they were. In Ireland, they are strictly used for cooking – in stuff like stews – not for eating raw. In Ireland they are regarded as the lowest quality tomatoes, while here they are regarded as the best?!

    Same for Strawberries, in Ireland they are small and tasty, here they are huge and bland. MY wife had strawberries in Ireland and confirmed that she had never tasted better.

  • pconroy

    I should add that when I was in Hawaii, the pineapples there were infinitely better than any ones I’ve ever had before or since. A local told me that there were 2 varieties that weren’t exported as they were too soft and juicy to survive transportation – of course these were the ones the locals ate almost exclusively.

  • dave chamberlin

    “The idea is to get the vegetable seed industry interested.” said Dr Powell.

    I have to disagree, demanding yuppies gave me wonderful coffee and beer, now they need to next clamour for a tomatoe that tastes like the heirloom varieties plucked straight off the vine. I am not waiting, I already grow tomatoes and thanks to my green thumb I grow enough for a small army. It is rediculously easy to grow tomatoes that yeild 50 pounds of tomatoes per plant. Only two things you can’t buy are love and homegrown tomatoes.

  • Kaviani

    Thanks for that last bit. Ed Yong overlooked it, and that’s exactly what I do (grow my own). I appreciate that you (wittingly or not) rope in meaningful themes beyond the topic itself.

    And to dave chamberlin’s point, the seed industry has absolutely no interest in this, at least not THE seed industry. I can see A&Ms doing it, though. In Texas they actually sell some of their patented products, so awesome GM tomatoes could be a real thing. I’m only against GM when it supports monocropping agribiz stupidity, not when it’s improving the quality and nutrition of a crop. I’m not above a tomacco.

  • Eurologist

    @ #6

    That’s well-known. (Too much) nitrogen enhances vegetative growth and increases water retention. Makes for more money on fruit and vegetables that are sold per pound, but does not increase the total amount of sugars, vitamins, etc. contained in the material. Conversely, it often delays ripening, makes the plants and fruit more prone to disease, often reduces shelf life after ripening, and may lower the total amount of beneficial or flavor compounds.

    There must be a lot of publications out there, here are a couple from a quick google search:

    http://hortsci.ashspublications.org/content/42/6/1490.full

    http://staff.unud.ac.id/~madeutama/wp-content/uploads/2009/06/vit-c-content-hort.pdf

  • dave chamberlin

    Home growers prefer strawberries and tomatoes that are indeterminate in when they ripen. Commercial growers prefer these fruits ( the supreme court overruled the biologists and made the tomatoe a vegetable-I am not making that up) to be determinate when they ripen. This is the primary factor, there are many, in making a tomatoe delicious or virtually tasteless. My tomatoe plants will ripen from mid July until the first killing frost, the plant is never overtaxed and the ripened fruit are extremely flavorful. The commercial varieties are harvested all at once and there lies the primary reason why a homegrown tomatoe tastes incomparibly better. The indeterminate variety produces as many flavorful fruit as it can at any one time. The determinate variety can’t possibly make all it’s fruit flavorful when it’s fruit ripen all at once.

  • pconroy

    @12 Dave,

    Right. There was a guy who grew strawberries near where I grew up, and still does, and he will only pick them:
    1. When they are ripe
    2. In the afternoon of a day when the sun shone in the morning

    He claims the #2 point is critical, as he claims that strawberries need about 2 hours or more of sun prior to picking, so that the sweetest and other flavors will be maximized.

    So if you drop by on a day with a cloudy morning, he won’t sell you strawberries!

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Gene Expression

This blog is about evolution, genetics, genomics and their interstices. Please beware that comments are aggressively moderated. Uncivil or churlish comments will likely get you banned immediately, so make any contribution count!

About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at http://www.razib.com

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