6 Comments

This is a different style than my usual material.* The setting and narrator is fictional – not me, but a character and scene invented for the story. The article is several years old now and the science is consequentially slightly dated.

Sitting on my balcony this early Spring morning, my elderly neighbour is planting a row carrot seeds.

She’s beaten evolution, that old lady.

Got it in a paper envelope that her bony hands pick seeds from and, rubbing her fingers, carefully space along the groove she’s made in the soil.

My neighbour isn’t at the mercy of Nature’s elimination of the unfit in the same way that elderly hyenas or hippopotamuses are. I’m sure she’s thankful for that, not that I can imagine her comparing her fate with African beasts.

We don’t have to suffice with what we can scavenge or kill, or die if we can’t. We grow grow food to suit ourselves. Elsie’s seeds are the accumulation of hundreds of years of selecting and breeding.

Evolution by man, not Nature.

Ancient carrots, were anything but orange, sporting a spectrum of white, yellow, green red, purple, and black. They were a thin, tough and rather bitter root.

Much later the sweeter orange carrots like those my neighbour is sprinkling in her back yard were selected and breed to honour the powerful House of Orange, the Dutch Royal Family, a family who also gave England a monarch, William the Third.

Those loyal horticulturalists crossed a pale yellow carrot from North Africa with existing red carrots yielding a sweeter vegetable in Royal family’s colours, the dominant colour of the Netherlands’ coat-of-arms and still the colour of the ’home’ shirts of the Netherlands’ football teams (soccer to some). A vainglorious reason for developing a new vegetable for sure, but modern breeding selects for pretty arbitrary reasons too.

Carrots have been consumed for thousands of years, but not always as a staple food. They have been variously regarded as an aphrodisiac, a medicine that could cure any number of diseases, and a religious object.

Afghan hill tribes in 900AD revered carrots as their golden colour reminded them of their god, the Sun, and munched on them thinking that they would earn righteousness by consuming of their deity’s likeness. (Or perhaps they were just after a sunnier disposition? Sharing this theme Catholics eat a wafer representing the body of their deity.)

Carrots are a recent horticultural development compared to other vegetables or crop plants such as wheat, corn, peas, cabbage (kale), potatoes or onion. We’ve been at this game a long time, and not just for food. Plants have have given materials for baskets, spears, musical instruments, and buildings like my neighbour’s wooden villa, which–like her–sags just a little to stand ever so slightly lopsided with age.

Evolution works, in part, by variety exploiting opportunities. Individuals of a species differ, the result of differences in their genetics. As conditions, food and predators change, those that are less well adapted give fewer offspring; those that survive more often pass their successful genes to the next generation. Thus, over time the species adapts to be a better match for it’s world.

There’s no special magic to this process. Take anything that varies and makes copies of itself and the better-adapted ones tend to survive more often than those that are not, so that over time the population contains more of the better-adapted individuals.

Over time we’ve developed another approach, selecting what might make better food, like all animals do, but rather than just eating them, we domesticate what we like and grow more of it. But more than that, we refine our food to make it ever more suitable to our needs and tastes.

Rather than be trapped by evolution, we have learnt to control the genetics underlying evolution. Evolution got us there and ever since we’ve been using breeding to evolve other species to suit ourselves.

Ancient carrots weren’t a particularly good meal, but the one’s we’ve breed since are.

As I watch Elsie work slowly around her vegetable patch, I find myself wonder if in a few years time, old ladies her like will be planting vegetables that are genetically engineered; if they’d know, or even care? They’d just be seeds in an envelope, after all.

Genetic engineering is a new twist selective breeding, but this time starting from an understanding of what genes code for what features of our food. It’s a detailed and rather fussy understanding that comes from many years of experiments probing the details of how life works and from the genome projects, projects that learn the DNA sequence that codes every gene in a particular plant or animal. It also have gathered it’s share of controversies, as new technologies do.

We’re still breeding, but this time starting with an intentionally modified plant or animal, rather than a few rare individuals that by random luck have a useful trait. The techniques used are more sophisticated than my neighbour grafting fruiting twigs onto her apple trees, but they are a grafting of sorts, too. New genes, or variations on existing ones, are placed into cuts made in the genome, just as the old lady adds fruiting stems to a host tree.

In Texas, researchers have modified carrots to absorb more calcium from the soil. Older women need calcium to ward off osteoporosis; others need it to address brittle bone disease. Dairy produce is a wonderful source of calcium, but also fattening. And, if you’re lactose intolerant you’d want to look elsewhere.

Eating vegetables with extra calcium might offer an alternative way to get more calcium to consumers in a way that is more universal with a leaner diet. Good things, veges.

Dr. Hirschi’s research group in Texas have been exploring how to alter carrots to take up and store more calcium.

Carrots get their calcium from the soil. A gene, cation exchanger 1 (CAX1), is part of a system that draws calcium from the soil and stores it within plant cell storage organelles called vacuoles. If these vacuoles were stuffed with calcium when you eat the plant, you’d add a dose of calcium to your diet.

The CAX1 gene has a neat self-regulation trick: the first portion of the CAX1 enzyme–made from the CAX1 gene–stops the CAX1 gene from making more CAX1 enzyme, easing off calcium absorption when there is calcium in the vacuoles.

Genetic engineering doesn’t always need to add new genes, but sometimes can work by altering existing ones. Members of Dr. Hirschi’s research group at the Vegetable and Fruit Improvement Center of the Texas A&M University, and colleagues elsewhere in the USA, made a shorter version of the CAX1 gene without the first bit, the bit that restrains it from storing calcium in vacuoles that already have calcium in them. Plants with this changed gene are more persistent at storing calcium and end up with a higher calcium content in their cell’s storage vacuoles.

Attempts at fortifying foods aren’t new. Golden rice adds beta-carotene to rice, a compound our bodes make into vitamin A. Carrots already have plenty of that: it’s what makes orange carrots, orange. (It gives oranges their colour, too.)

One potential problem is that while the plants might get more of the goodies, the people eating them have to get them too. This is more complex that it might at first seem: plants can contain chemicals that hinder the update of nutrients. Doubling the amount of calcium in carrot roots, doesn’t necessarily mean twice as much calcium for people who eat them. Spinach, for example, contains lots of calcium but also high levels of oxalate, which hinders calcium update.

Dr. Hirschi’s research group tested mice and people to see if they got more calcium by eating their new carrots: they did – they got about 40% more calcium.

Unfortunately, these carrots do not contain enough calcium to be a complete solution to your calcium needs. Adults need around 1,000 milligrams a day of calcium; the carrots Dr. Hirschi’s team tested have only about 26 milligrams of calcium for each 100 grams of carrot, compared to 15 milligram of calcium per 100 grams in the original carrots. If you wanted to get all of your daily calcium from just carrots, you’d need to eat about 4 kilograms of these carrots a day! Much as I like my carrots, that’s more a horse-sized meal than human-sized one.**

The level of calcium was roughly doubled in their new carrots, but not all of the extra calcium was taken in when eaten, suggesting that changing how the calcium is stored might help. Another approach might be apply the same strategy to a wider range of vegetables, since other vegetables such as potatoes and tomatoes can have the same modifications applied. Increasing calcium levels also has the side effect of increasing the firmness and possibly shelf lives of the vegetables.

I’ve little doubt old ladies will continue to plant seeds on Spring mornings. Maybe one day they’ll have extra calcium to help them continue to be spritely old folk.


Footnotes

Updated to add ‘more articles’ links that I overlooked! (See end of page.)

* I’ve mixed feelings about the style, but I’ve let it stand. It’s an old article, and there isn’t time to re-work it.

** Of course, people don’t get all of their calcium this way, and the aim wasn’t to replace all sources of calcium.

ResearchBlogging.orgBibliography

Morris, J., Hawthorne, K., Hotze, T., Abrams, S., & Hirschi, K. (2008). Nutritional impact of elevated calcium transport activity in carrots Proceedings of the National Academy of Sciences, 105 (5), 1431-1435 DOI: 10.1073/pnas.0709005105

Jeong, J., & Guerinot, M. (2008). Biofortified and bioavailable: The gold standard for plant-based diets Proceedings of the National Academy of Sciences, 105 (6), 1777-1778 DOI: 10.1073/pnas.0712330105

Enattah, N., Jensen, T., Nielsen, M., Lewinski, R., Kuokkanen, M., Rasinpera, H., El-Shanti, H., Seo, J., Alifrangis, M., & Khalil, I. (2008). Independent Introduction of Two Lactase-Persistence Alleles into Human Populations Reflects Different History of Adaptation to Milk Culture The American Journal of Human Genetics, 82 (1), 57-72 DOI: 10.1016/j.ajhg.2007.09.012

Wikipedia entry for ‘carrot’ (Accessed 14th August 2008; verified from references within and elsewhere)

Wikipedia entry for ‘House of Orange-Nassau’ (Accessed 14th August 2008; verified from references within and elsewhere)

Potato Genome Sequencing Consortium website

MedlinePlus entry on Lactose Intolerance (Accessed 14th August 2008)

National Digestive Diseases Information Clearinghouse (NDDIC, a site developed by the National Institute of Diabetes and Digestive and Kidney Diseases, NIDDK, of the NIH, USA): web page on Lactose intolerance (Accessed 14th August 2008)

eMedicine web page on lactose intolerance (Accessed 14th August 2008) (Author: Stefano Guandalini, MD, Director, University of Chicago Celiac Disease Program, Section Chief of Gastroenterology, Hepatology and Nutrition; Professor, Department of Pediatrics, University of Chicago Comer Children’s Hospital)


Other articles on Code for Life:

Haemophilia — towards a cure using genetic engineering

Temperature-induced hearing loss

Finding platypus venom

The inheritance of face recognition (should you blame your parents if you can’t recognise faces?)

Coiling bacterial DNA

Preserving endangered species — of gut microbes