Saturday, May 13, 2017

A GMO pineapple with a blush

A couple of months ago, I saw an article about a new "pink pineapple" that was being approved by the FDA and was a GMO. I've wanted to learn more about the variety, so in this blog post I'll be exploring the topic.

The pineapple was developed by Del Monte Fresh Produce (not to be confused with Del Monte Foods). The company plans to label it as "extra sweet pink flesh pineapple" and it will be grown in Costa Rica. In addition to pink flesh, it has a few other traits and we'll go through these one-by-one. Much of the information below came from the FDA submission documents.

Pink Flesh

To understand how the pineapple's flesh was made pink, we have to review how beta-carotene is made in plants. Beta-carotene is a pigment that has an orange color and is essential to us for vitamin A synthesis. We usually associate it with carrots. Its synthesized in plants in a multi-step process involving several enzymes. One of the intermediates in this pathway is lycopene, which is also a pigment but is bright red. Watermelon, tomatoes, and grapefruit are all fruits that are rich in lycopene. It is due to the accumulation of this pigment that the pineapple turns pink.

How was this accomplished? To make a pink pineapple, two things need to happen: a lot more lycopene needs to be made and its conversion to beta-carotene needs to be halted. To make more lycopene, the gene for phytoene synthase from a tangerine was added and was over-expressed (meaning that it was regulated in a such a way that the gene produced a lot of the phytoene synthase protein). This means that the crop can produce a lot more lycopene and beta-carotene.

However, the developers of the crop wanted lycopene accumulation without its conversion to beta-carotene. To achieve this, they silenced the lycopene β-cyclase (b-Lyc) and lycopene ε-cyclase (e-Lyc) genes in the pineapple using RNA interference. This is a naturally occurring defense mechanism that scientists have harnessed to silence genes by using the sequence of the gene itself. It triggers a pathway within the cell that chews up the RNA for the targeted gene. In this case, scientists added snippets of the b-Lyc and e-Lyc genes from the pineapple in a specific configuration. Once these snippets were turned on or expressed, it triggered the degradation of the lycopene-cyclase enzymes which are needed to convert lycopene into carotenes. Without this conversion, lycopene accumulates and the pineapple gets its beautiful pink colour.

File:Ghana pineapple field.jpg
Pineapple farm in Ghana
Image from Wikimedia Commons
By now you're probably wondering "Ok, pink pineapples are cool. But why?" Good question. The patent on the pineapple, which was published in 2013, claims "Carotenoids may contribute fundamentally to human health and in recent years there has been considerable interest in dietary carotenoids with respect to their potential in alleviating age-related diseases in humans." With a quick google search you can find tons of websites claiming that lycopene can do everything from preventing cancer to preserving bone health. Since lycopene is an antioxidant, there are a lot of websites that sell antioxidant supplements with information about the compound. However, there's little evidence supporting this.  The CDC states,"research studies have shown inconsistencies in the relation between carotenoid intake and protection from cancer." Regarding antioxidants, multiple studies have been conducted using dietary supplements and the NIH summarizes these findings by stating that "antioxidant supplements did not help to prevent disease."

Consequently, regarding this particular trait, I think that we should consider it as part of our diet rich in fruits and vegetables. As part of such a diet, it may help prevent disease. However, it's not a panacea that will cure you of your ailments. It's also a very stunning fruit from a visual perspective. Pineapple is a favorite in our house, so having a pink pineapple would be very nice to have on a fruit platter. And if that helps us eat more fruits, then why not have it as an option in our food supply? But if I'd had my choice in traits, I would have picked a pineapple that's easier to cut and handle :)

Alrighty, moving on to the next trait...

Controlled flowering

The second trait in the pineapple is controlled flowering. According to this paper: "A major limitation that afflicts pineapple growers is the phenomenon of natural flowering, which results in unscheduled fruiting. The percentage of natural induction is highly unpredictable and the incidence may vary from 0% to 100% in any given year (Kuan et al., 2005), which causes serious scheduling problems for growers and, in particular, fresh market growers".

Ethylene is a plant hormone that controls pineapple flowering, among many other things. According, to the same paper cited above, farmers currently use ethylene to "force" flowering which has been practiced for decades. This paper, which compared natural vs forced flowering, highlights that forced flowering "(a) advances flowering, (b) improves uniformity of flowering, (c) makes the harvest moment predictable, and (d) makes harvesting more uniform". The paper found that natural flowering was much more costly, but fruits produced by forced flowering were not as high quality as pineapples produced through natural flowering.

In 2006, a paper was published outlining that by silencing an enzyme involved in the synthesis of ethylene, they could delay natural pineapple flowering. The same idea was carried out in the making of the pink pineapple: an enzyme involved in the biosynthesis of ethylene (1-aminocyclopropane-1-carboxylic acid synthase) was silenced. This allows farmers to use ethylene to force flowering whenever they'd like so that all the pineapples can produce fruit at the same time.

I was left with a lot of questions about this trait, and I can only speculate on the answers. I imagine that the trait could reduce food waste on the farm. I do not know whether the need to apply ethylene increases the carbon footprint, if this is done mechanically. Ethylene ripens some fruits, however, the pineapple does not produce much ethylene to begin with, so I don't know what the silencing of ethylene synthesis does in this regards. 


The regulatory documents state that the GM pineapple is substantially equivalent to its control, with the exception of increased lycopene (which is expected) and decreased beta-carotene (which is also expected). The amount of lycopene present matched those of other fruits, such as watermelon. There were a couple of other metrics that were significantly different between the GM and the control, however, these were within the range of natural variation for the crop.

The crop will be labeled as "“Extra Sweet Pink Flesh Pineapple”. According to this article, the regular Del Monte pineapple is labeled as "extra sweet", so the pink one isn't any sweeter than "normal".


So, will I buy this pineapple? If I were to guess, I'd say that the company started working on this pineapple about 10 years ago when the antioxidant craze was at its peak. But 10 years later, that craze has fizzled away. I think the company has a pink pineapple that's visually beautiful, but has no real health benefit. I'd buy this pineapple if it doesn't cost more than usual. I'd like to know whether the controlled flowering trait reduces food waste, because if that's the case it would be worth paying a small premium. Otherwise... meh?

Man, I learned a crap ton about pineapples by writing this post... Let me know if you have any questions below.