3 Myths about Genetically Modified Crops

Genetically modified oilseed rape, one of the four main commercial GM crops. Photograph: David Levene

Genetically modified oilseed rape, one of the four main commercial GM crops. Photograph: David Levene

The debate about GM crops has reached a new level with many countries deciding on its fate. Among all this shrill and cacophony about it, we indeed have been fed many myths about it. Scientific American published a nice article on it some days ago, tiled – 3 Myths about Genetically Modified Crops . It looked into some detail about the 3 most important myths.

Lets have a look, shall we ?

Myth 1: GM crops have bred superweeds

Verdict: FALSE

This issue has been quite a contentious issue for more than a decade now.

US farmers had widely adopted GM cotton engineered to tolerate the herbicide glyphosate, which is marketed as Roundup by Monsanto in St Louis, Missouri. The herbicide–crop combination worked spectacularly well — until it didn’t. In 2004, herbicide-resistant amaranth was found in one county in Georgia; by 2011, it had spread to 76. 

Many scientists, and even some of my colleagues have argued that use of GM crops which are herbicide resistant are responsible for the evolution of herbicide resistance in many weeds.

Twenty-four glyphosate-resistant weed species have been identified since Roundup-tolerant crops were introduced in 1996.

However, herbicide resistance has been a problem for farmers regardless of whether they plant GM crops or not. For more see this chart on the rise of super-weeds:

‘The rise of superweeds’  Source: Scientific American

‘The rise of superweeds’
Source: Scientific American

So, blaming just the increased use of GM crops wont solve the problem of these super-weeds.

Myth 2. GM cotton has driven farmers to suicide

Verdict: FALSE

Now this has been a big news item in India recently when a leading rights activist and environmental campaigner Vandana Shiva alleged that some 270,000 farmers have committed suicide ever since GM crops have been used. Bt cotton which has a gene from the bacterium Bacillus thuringiensis has been planted in India and has been the major bone of contention in India.

Seeds initially cost five times more than local hybrid varieties, spurring local traders to sell packets containing a mix of Bt and conventional cotton at lower prices. The sham seeds and misinformation about how to use the product resulted in crop and financial losses. This no doubt added strain to rural farmers, who had long been under the pressures of a tight credit system that forced them to borrow from local lenders.

This claim was however refuted by researchers at the International Food Policy Research Institute in Washington DC, who scoured government data, academic articles and media reports about Bt cotton and suicide in India. Their findings, published in 2008 and updated in 2011, show that the total number of suicides per year in the Indian population rose from just under 100,000 in 1997 to more than 120,000 in 2007. But the number of suicides among farmers hovered at around 20,000 per year over the same period.

Suicide Rates and GM crops Source: Scientific American

Suicide Rates and GM crops
Source: Scientific American

The important thing to note here, is that the focus of argument in India has shifted from a balanced discussion on the various ways technology can benefit us to calls for outright bans on using it. This would never solve the issue but aggravate it.

Myth 3: Transgenes spread to wild crops in Mexico

Verdict: UNKNOWN

We finally come to another issue about how transgenes have spread to far-off maize fields in Mexico. What started all of it was:

In 2000, some rural farmers in the mountains of Oaxaca, Mexico, wanted to gain organic certification for the maize (corn) they grew and sold in the hope of generating extra income. David Quist, then a microbial ecologist at the University of California, Berkeley, agreed to help in exchange for access to their lands for a research project. But Quist’s genetic analyses uncovered a surprise: the locally produced maize contained a segment of the DNA used to spur expression of transgenes in Monsanto’s glyphosate-tolerant and insect-resistant maize.

Now, as GM crops are not approved in Mexico, the only possible source of such transgenes could only have come from GM crops imported from the United States for consumption and planted by local farmers who probably didn’t know that the seeds were transgenic. When the results were published it brought a furore in Mexico with people arguing for and against the issue. Ever since, few detailed studies have been done on the spread of transgenes via GM crops.

In 2003–04, Allison Snow, a plant ecologist at Ohio State University in Columbus, sampled 870 plants taken from 125 fields in Oaxaca and found no transgenic sequences in maize seeds.

But in 2009, a study led by Elena Alvarez-Buylla, a molecular ecologist at the National Autonomous University of Mexico in Mexico City, and Alma Piñeyro-Nelson, a plant molecular geneticist now at the University of California, Berkeley, found the same transgenes as Quist in three samples taken from 23 sites in Oaxaca in 2001, and in two samples taken from those sites in 2004.

In another study, Alvarez-Buylla and her co-authors found evidence of transgenes in a small percentage of seeds from 1,765 households across Mexico.

However, some scientists argue that transgene spread could in effect have a neutral or even a positive effect on local crops.

In 2003, Snow and her colleagues showed that when Btsunflowers (Helianthus annuus) were bred with their wild counterparts, transgenic offspring still required the same kind of close care as its cultivated parent but were less vulnerable to insects and produced more seeds than non-transgenic plants.

In the end, i would quote something from the article here:

Tidy stories, in favor of or against GM crops, will always miss the bigger picture, which is nuanced, equivocal and undeniably messy. Transgenic crops will not solve all the agricultural challenges facing the developing or developed world, says Qaim: “It is not a silver bullet.” But vilification is not appropriate either. The truth is somewhere in the middle.

What in fact, would be beneficial for ending the food insufficiency problems would be develop GM crops which would have more protein content, or even essential animal proteins or could produce various other required molecules in our body. These would benefit us in more ways than by simply developing GM crops for resistance to insecticides/ herbicides. The industry needs to look at developing a holistic view of GM crops and instead of creating shrill noise, detractors should sit together with the scientists from academia/industry,policy makers and industry honchos to use technology for our benefit.

For further reading:

1). Bt Cotton and Farmer Suicides in India: An Evidence-based Assessment, Guillaume Gruèrea & Debdatta Senguptaa,The Journal of Development Studies,Volume 47, Issue 2, 2011.

2). Field versus Farm in Warangal: Bt Cotton, Higher Yields, and Larger Questions, Glenn Davis Stone, World Development,Volume 39, Issue 3, March 2011.

3). Economic impacts and impact dynamics of Bt (Bacillus thuringiensis) cotton in India, Jonas Kathage and Matin Qaim, PNAS, 2012.

4). Are GM Seeds to Blame for Indian Farmer Suicides?, Adam Pugen, Feb 2013, The International.

Darwin Day !!

It's Darwin Day!

It’s Darwin Day! (Photo credit: Kaptain Kobold)

Darwin Day commerates the birth anniversary of Charles Darwin who was born on February 12, 1809. And on this day, various scientific institutions, agencies and bodies organise lectures and talks to highlight the awesome contributions of Darwin to science. Without his impressive array of work, science would have been quite bare and we quite ignorant about the inner workings of nature.  So, celebrate this day not in the name of Darwin but what science has done for the betterment of humanity in general. Think about all the inventions and discoveries science has brought us and let’s drink to it !!

So, what better way to celebrate this day  than to showcase the Bird-of-Paradise Project of Cornell Ornithology Lab.  The site gives a wonderful description of their project:

The birds-of-paradise are among the most beautiful creatures on earth—and an extraordinary example of evolutionary adaptation. On this site you can find what few have witnessed in the wild: the displays of color, sound, and motion that make these birds so remarkable. Then you can delve deeper, examining the principles that guided their evolution and the epic adventure it took to bring you all 39 species.

Have a look at it !!

More on this:

 

 

Genomic Evidence for Adaptation to Global Warming??

The "burning embers" diagram above w...

The “burning embers” diagram above was produced by the IPCC in 2001. (Photo credit: Wikipedia)

Global Warming – The ultimate quibble of this century !! Or should i say the “haute” of this century. Why? Now, common ask yourselves, which single topic apart from the religion/atheism debate, you always hear in any gathering or book reading circles or conferences or on social platforms which is ready to divide people into two opposing camps. Books are being written, movies made, debates fought and what for – “The legitimacy of Global warming”. Despite numerous evidences detractors still love to question it. However, a new paper published this month in PNAS provides genomic evidence for phenotypic responses to climatic warming.

What’s it all about?

Ongoing changes in regional climates, especially the trend of warming winters and blazing summers are pushing many species (both plants and animals) to shift their distribution toward higher latitudes and altitudes. Such a change in the species distribution, with an expansion in previously hostile areas and contraction in their own habitats which are becoming less favorable, can occur rapidly both in plants and animals. However, not all species can migrate to lesser hostile areas, and there are many reasons proposed for it. Primarily among them is the increasing trend of Habitat Fragmentation. Habitat fragmentation can result from human expansion into wilder areas resulting in few phenomena:

  • Reduction in the total area of the habitat
  • Isolation of one habitat fragment from other areas of habitat
  • Breaking up of one patch of habitat into several smaller patches
  • Decrease in the average size of each patch of habitat

As, a result of such human activity many species especially plants can’t migrate into other areas resulting into their dwindling numbers. But some species do survive in such increasingly fragmented habitats and hence have adapted to the climatic warming. Though some previous studies in Drosophila melanogaster have shown adaptive trait variation in relation to climate change in both natural and experimental population, however in some cases, the evolutionary response to climate change may be slow due to genetic constraints causing a time lag between the environmental change and an observed evolutionary response. Hence,understanding how various species track climate warming by genetically based adaptive trait variation and which traits facilitate the evolution of such adaption is important.

What is the new evidence?

Thymus vulgaris

The authors decided to look at Mediterranean wild thyme (Thymus vulgaris), a low growing herbaceous plant which is native to Southern Europe and is often used as a culinary herb. The plant contains many oils and the chemical composition(phenolic or non-phenolic) of it varies in different regions based on the temperature. These oils make a plant adaptable to freezing and hence different climatic areas have plants with varying composition of oils (chemotypes). So it would be worthwhile to see if the recent trend of gradual warming of extreme winter freezing events, has brought about an evolutionary response in plants i.e, has their chemical composition changed over time? Interestingly, any such change in the respective oil compositions in different climactic areas with different temperatures would have a genetic basis. And this is what the authors looked about.

The study area had a Mediterranean climate with summer drought but also severe winter freezing temperatures within the basin as a result of a dramatic temperature inversion In this area, there are six different chemotypes that are the expression of a genetically controlled polymorphism in T. vulgaris. Two phenolic chemotypes (carvacrol and thymol) are largely dominant on the slopes above 250-m elevation and four nonphenolic chemotypes (linalool, thuyanol-4, α-terpineol, and geraniol) below 200m elevation, where they experience the winter temperature inversion. Hence, phenolic chemotypes are predominantly winter non-tolerant whereas non-phenolic types are winter tolerant.

There is thus a sharp gradient in the chemotype frequency over only 3–5 km that goes from 100%of either phenolic or nonphenolic chemotypes to 100% of the other form, with a narrow transitional zone. In short, nonphenolic chemotypes show adaptation to habitats, which in the past have experienced extreme freezing temperatures in early winter, whereas phenolic chemotypes are sensitive to intense early-winter freezing and occur in habitats where extreme summer drought can exclude nonphenolic chemotypes.

Coldest annual temperature from 1955 to 2010 at the weather station of SaintMartin-de-Londres (filled squares), which occurs in the zone dominated by freezing-tolerant nonphenolic chemotypes, and from1970 to 2010 at the Centre d’Ecologie Fonctionnelle et Evolutive–Centre National de la Recherche Scientifique experimental gardens on the northern periphery of Montpellier (open circles), where natural thyme populations are dominated by freezing-sensitive phenolic chemotypes.

Hypothesis: Phenolic chemotypes (thymol and carvacrol) now occur in sites where they were previously absent or have increased their frequency in the transitional sites due to a relaxation of selection pressure normally associated with extreme early winter freezing temperatures due to climatic warming.

To do so, they compared the chemotype composition of populations observed in the early 1970s  to that in 2009–2010 for 36 populations sampled along six transects. Each transect was <10 km long, each containing six populations, with two “phenolic,” “mixed,” and “nonphenolic” populations.

They found that the mean percentage of phenolic chemotypes in a population was significantly (df = 35, S = 68.5, P < 0.01) higher in the contemporary samples (overall value of 53.1%) than in those of the initial study (47.7%) of 1970’s. The changes in composition of the initial nonphenolic populations were associated with the appearance of the thymol chemotype in all eight of the populations whose composition changed and the carvacrol chemotype in three of them.

The changes reported involved a reduced intensity of freezing events and changes in frequency of freezing tolerant and nontolerant phenotypes in natural populations of the Mediterranean aromatic plant, Thymus vulgaris. A significant appearance of freezing-sensitive phenolic chemotypes in sites where they were historically absent and an increase in their frequency in previously mixed populations was observed. Such changes have occurred in 17 of the 24 populations where they could potentially occur.

Such studies, illustrate that a rapid evolutionary response to temperature modifications can occur where genetic variation is combined with a change in a previously strong selection pressure, even for a perennial woody plant. Hence, this provides quite a neat example of genetic changes brought about by climatic warming.  I guess, the detractors of global warming would be feeling quite uneasy now !!

More on this:

  1. Genetic consequences of climate change for northern plants, Alson, Proceedings of Royal Society B, 2012.
  2. Climate extremes: Observations, modeling, and impacts, Easterling DR, Science, 2000.
  3. Ecological and evolutionary responses to recent climate change, Parmesan C, Annu Rev Ecol Syst Evol, 2006.
  4. Ecological responses to recent climate change, Walther GR, Nature, 2002.
  5. Rapid shifts in plant distribution with recent climate change, Kelly AE, Goulden ML, Proceedings of National Academy of Sciences, 2008.

  6. The distributions of a wide range of taxonomic groups are expanding polewards, Hickling R,Global Change Biology, 2006.
  7. A globally coherent fingerprint of climate change impacts across natural systems, Parmesan C, Nature, 2003.

  8. Running to stand still: Adaptation and the response of plants to rapid climate change, Jump AS, Ecology Letters, 2005.
  9. Genetic response to rapid climate change: It’s seasonal timing that matters, Bradshaw WE, Molecular Ecology, 2008.

  10. Climate change and evolutionary adaptation, Hoffmann AA, Nature, 2011.

To quiver or to shiver !!

The title of this post – To Quiver, or to Shiver is taken from a new article published this month in Proceedings of Royal Society London B. The paper deals with an interesting question – If a organism is good at one thing, does it mean that its good at all others too? OR Do you have to pay a price for being the best at something?

What is it all about?

Parasemia plantaginis coll. Mus. Zool. Oulu

Parasemia plantaginis coll. Mus. Zool. Oulu (Photo credit: Wikipedia)

Wood Tiger Moths, a species of moth(Parasemia plantaginis) found throughout Europe are widely known for their different wing colourations depending on the place they live.

Now why would this moth have bright colours?

Wouldn’t it attract more predators and hence get eaten up?

It turns out colours are used by various organisms as a predator-defence strategy. There can be two kinds of colouration schemes:

  • Camouflage:It  is one colouration-based predator defence strategy and benefits from variable coloration, which prevents predators from developing a search image for the most abundant phenotype of prey.Because, if the prey have a consistent camouflage colouration then the predator would after a few trials and errors, learn to identify the prey easily and then the prey would be wiped out due to the predation pressure.
  • Aposematism: Situated at the opposite end of the predator aversion strategy spectrum, where prey use conspicuous warning signals to advertise their secondary defences. Warning signals of such organisms are not expected to vary much because predators should learn to avoid a uniform signal more efficiently than a variable signal, leading to greater survival.

Now, Wood Tiger Moth the species in question as seen in the picture above show aposematism and use these conspicuous colours as a warning signal towards predators. But, contrary to the predictions for this warning signal homogeneity,  many such moths possess variable warning signals.

So, if uniform colouration is so important for predator defence, then why does the Wood Tiger Moth show variation in colours?

One reason could be that though different hindwing colours (white or yellow) ,in case of Wood Tiger Moth form the basis of predator defence but as one goes towards the Northern Latitudes, melanization or a general blackening of the hindwing is necessary for maximal absorption of sunlight or thermoregulation.

The general blackening to which i refer is the deposition of melanin, a process called melanization. It is used by many organisms including us !! Its benefits include immune response, thermoregulation etc.

To give you an example, see the below picture of the samples which the authors took from Europe.

Picture1

A map showing the sampling sites between Estonia and northern Finland, and the Alpine region. Each site is represented by a pie chart with varying amounts
of black representing the mean percentage of hindwing melanization of individuals captured at that site. Moths featured in (a) display the range of melanization observed in Estonia, Finland and the Alpine region, and (b) represent other levels of melanization found only in the Alpine Region

So, in general as one can see in the Alpine regions where the sunlight is very rare for the whole year, the moths have  less than 20% colouration !! (see, picture above (b))

But why??

It seems that higher melanization limits the amount of other pigments important in the warning signal, thereby setting the stage for a trade-off between defensive signalling and thermoregulation.

The question which the authors looked upon is something like this:

Do variation in male hindwing melanization is linked to thermoregulation and/or involved in a trade-off with protective benefits of colour ?

What did they find?

The authors started off with a combination of field based studies and predation experiments with artificial moths. Have a look at them:

Picture1

The artificial moths used in the experiment: (a) the complete repertoire (b) one of the authors with a moth

  • The amount of melanization increased with increasing latitude in Wood Tiger Moth males from Estonia to north Finland.
  • Individuals in the Alps had a significantly greater amount of melanin covering their hindwings than those in central Finland.
  • Melanization also varied more among individuals in the Alpine region compared with central Finland.
  • Greater melanization also increased the average rate for warming up for the moths.
  • Every 10 per cent increase in the amount of melanin resulted in a 16 per cent increase in the odds of being attacked.

Taken together,the results show the likely existence of a trade-off between thermoregulation and predation risk with respect to the amount of melanin present on the hindwing in Wood Tiger Moths. Specifically, what they found was that greater amounts of melanin in both white and yellow males resulted not only in an increased ability to absorb radiation, but also increased the likelihood of attack by avian predators. The results provide evidence that the differences in costs and benefits of melanin in the two locations can drive phenotypic differences in the warning signal of males on broad and local geographical scales.

Take home message:

If an organism is good at having X, then it must come at some cost. And as X is very costly it does not mean that its not a successful strategy, if the benefits of the costly strategy(X) outweighs the high cost  !!

More on this:

  1. The redder the better: wing color predicts flight performance in monarch butterflies, PLoS One, 2012.
  2. Linking color polymorphism maintenance and speciation, Gray SM, McKinnon JS, TREE, 2007.
  3. Insect melanism: the molecules matter, True JR., TREE, 2003.
  4. Visual predators select for crypticity and polymorphism in virtual prey, Bond AB, Kamil AC., Nature, 2002.

Garden in a Bottle, anyone?

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Internet has been buzzing for the past few days with this quite an astounding news about The Man with a Garden in a Bottle. So, what extraordinary thing is this?

The most important thing to know about it is that for the past 40 years it has been completely sealed from the outside world. Inside is a healthy growing ecosystem comprised only of Spiderworts. The bottle garden has created its own miniature ecosystem. Despite being cut off from the outside world, it has been able to photosynthesise as its kept near to a window in Mr. Latimer’s house. It was revealed to the world quite recently when he took a photograph of it to the BBC Radio 4’s Gardeners’ Question Time and asked the panel of experts if it is ‘of scientific or horticultural interest’.

So, how does a bottle garden work?

Bottle gardens work as the sealed space they are in creates a completely self-sufficient ecosystem in which plants can survive by using photosynthesis to recycle all the nutrients available. The only external input needed to keep the plant going is light, since this provides it with the energy it needs to create its own food and continue to grow. The sunlight falling on the plant leaves is absorbed by proteins containing chlorophyll. Now, some of that light energy gets stored in the form of adenosine triphosphate (ATP) molecules. The rest is used for removing electrons from the water which is absorbed from the soil through the roots. These “free ” electrons get used up in chemical reactions  which convert carbon dioxide into carbohydrates, hence releasing oxygen.

But the ecosystem also uses cellular respiration to break down all the decaying material which is shed by the plant. The bacteria present in the soil of the bottle garden absorbs all the plant’s “waste oxygen”, hence releasing carbon dioxide which the growing plant then can reuse. During night time, when there is no sunlight for  photosynthesis, the plant uses cellular respiration for its basic functions by breaking down the stored nutrients.

Because the bottle garden is a closed environment, that means its water cycle is a self-contained process. The water present in the bottle gets taken up by roots and is then released into the air during transpiration, which condenses into the potting mixture, where the cycle begins again.

So, if you want to go ahead and make a bottle garden of yours this video might help !!