Science News

Go bananas for vitamin A

Fri, 20th Jun 2014

Chris Smith

Bananas genetically modified to beef up their vitamin and iron content havecommon form of eating a banana been unveiled by Australian researchers.

The problem that Queensland University of Technology's James Dale and his colleagues were trying to address is chronic vitamin A and iron deficiencies amongst the populations of some countries, Uganda among them, where bananas are a food staple.

"People there might cook and eat up to a kilo of bananas a day," says Dale.

"But the native fruit can be very poor sources of certain micronutrients including vitamin A, so people eating them frequently can become deficient, leading to a range of diseases including blindness."

The approach taken by the team was to produce a banana rich in the chemical precursor for vitamin A, an orange-coloured molecule called beta-carotene. When eaten, this beta-carotene is split into two vitamin A molecules in the body, in proportion to a person's vitamin A requirements, so there is no risk of vitamin A poisoning.

To do this, the team borrowed genes from other banana strains, including the Asupina from Papua New Guinea, which, owing to the presence of an altered form of a gene called phytoene synthase, naturally contain much higher levels of beta-carotene.

At the same time, to pep up the iron content of the fruit to help consumers fend off anaemia, the researchers increased the expression of a molecule called ferritin, which works like a molecular cage capable of trapping iron. By also increasing the mobilisation of iron in the plant through other genetic manipulations, the result is far more iron finding its way into the fruit, where it lodges in the ferritin until eaten.

Dale doesn't know if his modified bananas still taste okay - or at least he's not admitting to a sly bite or two - but he's about to find out thanks to the granting of a license to commence a human feeding shortly.

Meanwhile, data from gerbils, which metabolise beta-carotene and vitamin A very similarly to humans, suggests that the fruits pack an effective nutritional vitamin punch. But are the bananas safe, and could there be any risks?

Banana plants don't release pollen and generally need to be propagated by taking cuttings, so environmental control of the modified strains shouldn't be a problem. As to the chemistry of the fruits themselves, having tested them with chromatography techniques, Dale is confident that the chemical make up has not been altered beyond the enhancement of iron and beta-carotene.

But will it work? The proof really will be in the eating...

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Well, the concept of genetically modifying foods to improve their nutrition value and for other purposes has been around a while, but is controversial. Some people claim that certain genetic modifications have caused allergic reactions in certain people. There is clear promise here, but I don't think we will know the entire story for some time. Atomic-S, Sat, 21st Jun 2014

Even today we mostly eat genetically modified foods--ever seen wild corn or wild strawberries? Now, this modification was mostly done by breeding (and cross breeding) over the last few thousand years, so I know it is not the exact same ethical/philosophical dilemma as that posed by overnight genetic manipulation in a laboratory, but it is good to bear in mind that very few of our fruits, vegetables and livestock (yes, even the "organic" ones) are as they were in nature 10,000 years ago.

I guess I would break genetic modification into 7 categories, each with a clear distinction from the others, and their own set of potential benefits, and potential pitfalls:

1) Natural evolution--this is very slow, and doesn't necessarily lead to traits considered "desirable," however, there is something to be said for random mutations--sometimes the best solutions are not predictable, no matter how well we understand the problem, or how hard we try to solve it.

2) Selective breeding--we have been doing this for thousands of years, and it has been quite successful. It is much faster than natural selection, but still requires several generations to amplify "desirable traits." There are several pitfalls here too: "over-breeding" can lead to amplification of undesirable traits as well (hemophilia, for example); and cross-breeding can lead to mules, or species with difficulty procreating without human intervention...

3) Cis-genic manipulation--this is the splicing of genes from multiple members of the same species. In theory, the resulting life forms would still be considered members of the same species, and there would be no outcome that would not be possible from breeding alone. The main difference here being the significant reduction in time required (single generation strategies) and better control of phenotype.

4) Trans-genic manipulation--this is splicing of genes from multiple species. This widens the available geno- and phenotypes dramatically, and allows for the creation of some truly chimeric organisms. Here there is much more difficulty in predicting the outcome (or even viability) of the organisms, and there is a greater chance of unforeseen negative consequences.

5) Novo-genic manipulation--this involve synthesizing one or more genes in the lab, and splicing them into the genome of a trans-genic or cis-genic (or natural) organism. This increases the available palate exponentially (in the literal, not mathematical sense). There is also much greater problem in predicting outcomes, which also can be much more alien than anything achievable with existing ("proven") genes. The resulting proteins could be incredibly toxic, or cause severe allergic reactions, or perform any number of unknowable (dis)functions. People are only now just being able to perform these types of manipulations in the lab.

6) Totally synthetic biology (still DNA- or RNA-based)--why use an existing template, when you can write the whole book? This is the most difficult (as far as I know, no one has done this yet), and offers the greatest range in potential utility and disaster.

7)Totally synthetic biology--why use an existing alphabet when you can invent your own (or at least add a few letters)? There has been some limited success in making synthetic base pairs, but it has a **really** long way to go before we would see any practical use of these techniques (I think)...


There are also ways of tampering with gene expression, signal transduction etc. (epigenetics) that I don't understand at all, so I won't go there. chiralSPO, Sun, 22nd Jun 2014

Natural evolution has produced plenty of allergens and toxins. Food is by definition anything digestible that doesn't produce an unacceptable allergic or toxic reaction.

I really don't see any matter of ethics or philosophy in this so-called "debate". Farmers "play god" every day by deciding what should live or die, and how to manipulate nature to produce stuff people want to eat. What's wrong with doing it in a small laboratory instead of a big one?  alancalverd, Thu, 26th Jun 2014

I will say that people commonly ingest vitamins, and all sorts of dietary supplements.  Milk has been fortified with Vitamin D for quite some time, and salt has had iodine added. 

Would we be better off if the cows could be bred to produce vitamin D rich milk rather than adding as a supplement later?

Research in the fields of genetically modified foods may be progressing faster than we can test the foods.  In many senses, other contributors are right that there is little difference between GM, and what might be able to be achieved with hundreds, or thousands of years of selective breeding. 

One of my concerns is the increasing use of toxins in our environment.  Some GM foods help improve plant resistance to pests, and thus require less spraying.  However, other types of GM foods allow spraying of broad spectrum herbicides directly onto the crops. CliffordK, Fri, 27th Jun 2014

"Roundup-resistant" crops are probably the ultimate high-yield monoculture, provided that the final product can be shown to contain a negligible level of glyphosate. Fortunately testing for glyphosate is fairly easy, so as long as you buy your food from a large supermarket or major manufacturer, you and the farmer will get a good deal on clean, healthy, affordable, bug-free cereal products. Or you can buy an "artisan" organic cereal for at least twice the price, fertilised by shit and piss, weeded by slave labour, and infested with all those bugs and bacteria that are resistant to nicotine and pyrethrin.    alancalverd, Fri, 27th Jun 2014

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