
GMO corn has metabolism disturbances caused by the transformation process - randomname2
http://www.nature.com/articles/srep37855
======
Obi_Juan_Kenobi
I can tell that no plant geneticists reviewed this paper, certainly no maize
geneticists.

The authors claim to use a 'near-isogenic' line for a control.

> The varieties of maize used in this study were DKC 2678 Roundup-tolerant
> NK603 (Monsanto Corp., USA), and its nearest isogenic non-transgenic control
> DKC 2675

Yet no mention of how 'near' these lines are is made, nor is the seed
provenance discussed. This is, frankly, absurd, as the Monsanto transgenic
line began development decades ago. Presuming that the other inbred had been
established at that point, there is a minimum of 20 years that these inbreds
have been independently maintained.

A proper experiment would have introgressed the EPSPS transgene into a known
inbred. That is the _only_ way you can ensure that you have a consistent
genetic background, and is standard practice in the maize community. This is,
almost without exception, reported in a manuscript. It is that important.

To contextualize this, I've compared control groups of a particular inbred
(e.g. B73, Mo17, A619) and seen substantial differences in RNAseq data, simply
because it was seed stock from different labs. These are lines that have been
shared within the past 10 years. The B73 inbred (from which the maize genome
was/is sequenced) is notorious for being defined as 'a barrel of seed in Mike
Freeling's lab'. Honesty, the sheer diversity of maize, along with wind
pollination, complicated field conditions, and undergraduate help =P, make all
maize inbreds a moving target.

This is not a small detail of the paper; all the results rely on these lines
actually being 'near-isogenic'. Any small differences between them can easily
account for the observed differences. Hell, even after 3 or 4 rounds of
introgression, you can often visually see differences between lines that
aren't actually due to the trait in question; it's just background noise.

Whatever your views on transgenic technology, I would not base any decision on
this work.

------
cossatot
Note for comments-first readers: this shows differences in _corn_ metabolism,
not in humans or other animals that have consumed the corn. However they
reference studies where rats had worse health after eating GMO corn vs normal
corn.

~~~
makomk
In a sense this probably isn't terribly surprising; GM corn is known to have
reduced yield due to disruption from the genetic modifications. The
interesting part is that the composition of the resulting corn differs as a
result of this in ways that weren't expected or previously known.

------
toufka
The research compared an original strain to a modified strain, to the modified
strain with roundup. It is unsurprising that the modified strain, that is
producing an extra protein in high amounts will be under a heavier metabolic
load than the same strain that is not producing that extra protein. It seems
the metabolic load showed up in a few particular places that haven't obviously
been investigated before, and now we can more carefully probe those
differences now that the team did a thorough screen to find them.

However, what the research did not do is compare the metabolic load in the
modified strain to anything else. They did not compare it to an average corn
strain, an 'heirloom' corn strain, a corn that is under cold/heat/viral or any
other kind of environmental stress or bounty. Nor did they compare the corn
metabolite levels to other foods. I suspect the difference in metabolic load
between a strain +/\- a particular resistance protein is likely less than the
difference in metabolic load between various corn strains, much less the
difference between fertilized/shaded/cold-conditioned corn, much less the
original grass strain from which human-edible corn came from, much less from
another food crop. The difference appears in the ratio of particular
metabolites in the corn. And at the end of the day the difference in amounts
of small molecules upon adding this metabolic stress is likely completely
overwhelmed by the literal amount of material (ex. if you don't want that much
of the metabolite, use 0.01% less corn. And if the corn is processed at all,
this kind of difference becomes moot very quickly.)

The result is not surprising and is framed in a particularly click/news-bait
worthy way. The nice part of the research is that it did a lot of hard work to
find the variables that now can be looked for in those above cross-wise
comparisons without having to do the major hard work of screening an entire
transcriptome for each comparison. But it does not in any way provide evidence
for any danger to human health at all.

Some math:

The modified strain's largest difference in metabolites was a 28x increase in
cadaverine (btw, it's pretty entertaining how many nitrogen-containing
compounds have fantastic names because of their odor). According to [1] the
difference in the amount of cadaverine between dried and canned corn is 5.5x
(with the _low_ cadaverine in dried corn mentioned as nutritionally
deficient). And the total amount of cadavarine in fresh corn is ~ 10mg/100g
which is ~ 0.01% by mass. Most of the other large changes in metabolites were
changes of less than an order of magnitude.

[1]
[http://www.sciencedirect.com/science/article/pii/S0308814611...](http://www.sciencedirect.com/science/article/pii/S0308814611014129)

~~~
Obi_Juan_Kenobi
Yes, the proper comparison would be an additional transgenic strain expressing
a suitably 'inert' protein to thus differentiate between the metabolic demands
of high levels of protein expression vs. some particular effect of the
heterologous EPSPS. Ideally, you'd use the same protein with a deletion of an
active domain. It is common use multiple deletion lines to identify the
causative domain; this sort of mechanistic work is essential for understanding
what is actually going on.

Moreover, the use of 'near-isogenic' lines is very troubling, as they are
rarely that similar. You can do e.g. RNAseq on 'identical' inbreds from
different labs and get substantial differences. Seed is passed around so much,
mis-labled in the field or out, etc. They certainly do not have an identical
inbreed from something that was developed decades ago, not even close. Calling
them near-isogenic is, well, let's say 'not that honest'. Very important to
note that they have no way to control for this difference in genetic
background.

Also noteworthy; Michael Antoniou has co-authored papers with e.g. Seralini,
notorious for a widely-discredited paper on RoundUp
[https://en.wikipedia.org/wiki/S%C3%A9ralini_affair](https://en.wikipedia.org/wiki/S%C3%A9ralini_affair)
That certainly does not discredit this work, but it is concerning when an
investigator agrees to co-author a manuscript of such poor quality.

Finally, having done a lot of work on '-omics' in plants, I've yet to see an
experiment that doesn't turn up some differences. Their list of GO terms is
not remarkable, and changes of '30 fold' are not nearly as dramatic as they
appear. This is well within the range of what I'd expect to see between
different similar inbreds, which these lines certainly are.

------
sebleon
Great article! Curious to see how GM industry will react, same-ness has been
one of the big arguments against labelling GMO food.

~~~
mgamache
They will criticize the research with hired 'thought leaders' and point to the
'overwhelming evidence' that proves GMOs and roundup is safe.

~~~
cmdrfred
I'm confused. Your argument appears to be that GMO corn and roundup is unsafe
for corn? This paper doesn't have anything to do with human consumption.

~~~
mgamache
Let me be more specific: the question was "how will the GM industry will
react"

‘substantially equivalent’ is a proxy for food safety and it's also a tricky
standard. When interpreting this study's results the public and policy makers
will look to academics:

[http://www.nytimes.com/2015/09/06/us/food-industry-
enlisted-...](http://www.nytimes.com/2015/09/06/us/food-industry-enlisted-
academics-in-gmo-lobbying-war-emails-show.html)

Just by selectively funding academics that agree with them they can distort
the debate.

~~~
cmdrfred
So do you have evidence it is unsafe or just are you simply against any
organization that uses lobbyists? (Teachers unions, ACLU, Climate and Gay
rights organizations, etc)

~~~
mgamache
I didn't say anything about lobbyists. I do have an issue with supposedly
unbiased experts being on a private payroll without full disclosure all-
around. Would you be okay with a NY Times reporter getting funding for a story
from Monsanto (without disclosure)?

~~~
grzm
If I'm understanding you correctly, I think you might be blurring the lines
here. A NYT reporter is a journalist, not an expert. They may use experts as
sources for their stories. I agree that it would be a serious breach of ethics
for a journalist to take money from Monsanto. It's not the same as an expert
receiving funding from industry. That has it's own ethics issues, which I
think are the ones you're getting at.

