3554315659_58ffc0bbda.jpg“Apple, Peaches, Pumpkin Pie….”

After the initial reports in 1983 of successful genetic transformation of tobacco, petunia and sunflower plants using Agrobacterium to mediate gene transfer, this technique was tried on many other crop plants.

By 1989, a colleague at the time summarized a “Plant Gene Transfer” meeting he’d attended by singing the line “Apple, Peaches, Pumpkin Pie….” from the 1967 hit song by Jay & The Techniques.

It was almost easier to name the crop plants NOT reported as being genetically modified using Agrobacterium.

There were, however, a very important group of crop plants not amenable to this transformation technique. The cereals.

Corn (maize), wheat, barley, oats, etc., all resisted efforts at genetic transformation using the Agrobacterium-based technology. The reasons are complex, but suffice it to say here that it was mainly due to the fact that they are all monocots. The cereals not only don’t serve as good hosts for Agrobacterium, but also can’t be regenerated very easily via tissue culture, which is a critical step in Agrobacterium-mediated genetic transformation.

So, what were the poor cereal breeders to do?

Shotgunning DNA

In 1988, it was reported (see ref. 1 below) that maize could be genetically transformed by bombarding maize embryos (isolated from seeds) with extremely small tungsten micro-projectiles (0.6 or 2.4 microns in diameter) coated with DNA. Thus, these researchers avoided having to use Agrobacterium to deliver the foreign DNA into plant cells and, by using maize embryos, the necessity of generating plants from somatic cells.

And so the gene gun was born.

Information about the Biolistic®-PDS-1000/He Particle Delivery System, e.g., can be found here. (And you may even be able to buy a used one for $100!)

So, by 1990, there were multiple ways to genetically transform plants. And the race was on to develop commercially available (and profitable) GMOs.


The first GMO approved by the USDA for human consumption was the “Flavr Savr” tomato in 1992. And by 1996, Roundup Ready® soybeans were sold by Monsanto. As indicated in the graph above, both herbicide-tolerant (HT) and insect-resistant (Bt) genetically engineered (GE) crops have been widely adopted by U.S. farmers. (For more info click on figure.)

Though their GE crops have sold well, biotech companies want to protect their investments by limiting or preventing the ability of growers to save seeds from GE crops. One way is through litigation. Another way is through technology.

“Terminating” Seed Germinationthe-terminator.jpg

Officially called the Technology Protection System (TPS), a way was found to block the germination of seed produced by GE plants.

Briefly, this so-called “terminator” technology incorporates genes into GE plants that, when expressed, are lethal to seed embryos. (see ref. 2 below for more information)

T-GURTs Are “Traitors”

Another technological way to prevent farmers from saving and replanting seeds from GE crop plants would be to incorporate traits into the GE plants that would require a special chemical for second-generation seeds to germinate. Sort of like a special key for the lock.

Officially known as Trait-specific Genetic Use Restriction Technology or T-Gurt (a.k.a., “Traitor” technology), this method incorporates a genetic control mechanism that requires yearly applications of a proprietary chemical to activate desirable traits. (see ref. 2 below for more information)

Bottom Line: These days, the genetic transformation of plants, even cereals, has become routine. And there are even ways to insert “locks and keys” into your GE plants.


1. Klein, T.M., Fromm, M.E., Weissinger, A., Tomes, D., Schaaf, S., Sleeten, M. & Sanford, J.C. (1988) “Transfer of foreign genes into intact maize cells with high-velocity microprojectiles.” Proceedings of the National Academy of Sciences (USA) Vol. 85, pp. 4305-4309. (PDF)

2. “Terminator” Technology, Department of Soil and Crop Sciences, Colorado State University.

HowPlantsWork © 2008-2011 All Rights Reserved.

Animal, Vegetable, Miracle - Vegetannual.jpgWhere Do New Plants Come From?

Well, new plant species arose (and still arise) through plant evolution, that is, as a consequence of hundreds of millions of years of natural selection.

About 12,000 years ago, however, humans got involved.

Early examples of humans trying to manage plants for their benefit likely included burning of forests to encourage herbaceous plants, the vegetative propagation of plants using tubers (think yams, e.g.), and, of course, the saving and sowing of seeds from “desirable” plants.

After people began domesticating plants, things got a bit more interesting. They began producing so-called “cultigens”, that is, plants that have been deliberately selected by humans, a.k.a., “artificial selection”.

1761o.jpg Thus, the field of plant breeding commenced. (An excellent book on this subject is Hybrid: The History and Science of Plant Breeding)

On the left is shown an Assyrian relief carving from 870 B.C. depicting the artificial pollination of date palms.

So, even though they didn’t know the scientific basis of plant breeding, humans were apparently actively engaged in it nearly 3,000 years ago.

Remarkably, this lack of understanding of the genetic basis of plant breeding was true even up to the early twentieth century, until, of course, the experimental results of Gregor Mendel were discovered and disseminated.

Besides the production of plant hybrids via cross pollination, new plants can also be made by the ancient art of grafting and the relatively new technique called transgenics, a.k.a., plant genetic engineering. (Since I’d like to focus on transgenics, I’ll refer you to an excellent introduction to grafting here.)

1977 – The Genie Emerges From The Bottle

Though humans have been making new plants for thousands of years, they’ve only been making transgenic plants for about 30 years.

Most agree that the era of plant genetic engineering began when a scientific paper was published in 1977 showing that a pathogenic bacterium by the name of Agrobacterium tumefaciens was able to insert some of its own genes directly into the genome of its plant hosts.

This research was conducted at the University of Washington (UW) in Seattle primarily by Dr. Mary-Dell Chilton, who was then a postdoc, working with Prof. Milton Gordon and Prof. Eugene Nester, in the departments of Biochemistry and Microbiology, respectively. (Among her honors, in 2002, Dr. Chilton was awarded Franklin Institute Award in Life Science, and, in 2008, was profiled in Scientific American.)

As a graduate student in the Botany Department at UW at the time, I remember attending a seminar by Dr. Chilton reporting this discovery. As I recall, the implications of this finding regarding the potential genetic transformation of plants was certainly recognized at the time. That is, that Agrobacterium could potentially be used as a means to deliver foreign DNA, i.e., a genetic vector, into plant cells, thus genetically altering them.

Remember that by 1977 scientists knew how to cut and paste genes (recombinant DNA) and regenerate whole plants starting with only a few plant cells using plant tissue culture. So the implications of this 1977 paper were enormous.

Fast-forward to 1983 –

Transgenic plants were first created in the early 1980s by four groups working independently at Washington University in St. Louis, Missouri, the Rijksuniversiteit in Ghent, Belgium, Monsanto Company in St. Louis, Missouri, and the University of Wisconsin. On the same day in January 1983, the first three groups announced at a conference in Miami, Florida, that they had inserted bacterial genes into plants. The fourth group announced at a conference in Los Angeles, California, in April 1983 that they had inserted a plant gene from one species into another species.” (from ref 2 below)

To be continued….

1. Three Ways to Make a New Plant, The Exploratorium, San Francisco, California.

2. Transgenic Crops: An Introduction and Resource Guide – History of Plant Breeding, Colorado State University.

HowPlantsWork © 2008-2011 All Rights Reserved.

DIYbio.jpgBiotech in Your Garage.

Is it possible that the kids across the street could someday soon be creating genetically engineered plants in their garage or greenhouse? (Now there’s a scary thought.)

This may be more feasible than you think.

An article called Garage Biology in a recent issue of Nature magazine (see ref. 1 below) attracted my attention to the burgeoning field of “do-it-yourself” (DIY) biotech.

For relatively modest amount of money, a person can set up a reasonably functional molecular biology lab, in part, by acquiring used lab equipment in places such as eBay. See, for example, this garage biology lab in Silicon Valley.

The above article is mainly about Dr. Rob Carlson, a pioneer in the field of “garage biotech” (see refs. 2 & 3 below). He has recently published a book called Biology Is Technology: The Promise, Peril, and New Business of Engineering Life. According to one prominent reviewer: “Since Rob Carlson is THE authoritative tracker of progress in biotech, this book is the most complete – and exciting – chronicle of the technological revolution that promises to dominate this century.” –Stewart Brand, Author of Whole Earth Discipline: An Ecopragmatist Manifesto.

fruit_helix.jpgInformation regarding “biohackers” can, of course, be found online (e.g., see ref 4 below).

But even if you don’t have the money or knowledge to do such science yourself, there may actually be community biotechnology labs in your city (e.g., see ref. 5 below) that provide the training and equipment. A DIY Biotech hacker space has recently opened in NYC.

So, similar to open source computer software, does there exist a growing field of “open source biotechnology”. Some say yes, but others say no.

Regardless, the recombinant DNA genie is out of the bottle (so to speak), and the knowledge and equipment required to perform gene splicing can easily be acquired (or built).

And getting such recombinant DNA (artificial genes) transferred into plants is relatively easy (compared to animals).


See here and/or here, for example.

But for a sobering look at the current limitations of so-called “synthetic biology“, please see reference 6 below.

Here’s a new book on the subject: Biopunk: DIY Scientists Hack the Software of Life


1. Ledford, Heidi (2010) “Life Hackers.” Nature Vol. 467, pp. 650-652. (PDF)

2. Carlson, Rob (2005) “Splice It Yourself: Who needs a geneticist? Build your own DNA lab.” Wired, Issue 13:05. Splice It Yourself

3. Rob Carlson’s Blog

4. DIYbio.org WebsiteDIYbio.org is an organization dedicated to making biology an accessible pursuit for citizen scientists, amateur biologists and biological engineers who value openness and safety.

5. GenSpace – New York City’s Community Lab GenSpace is a nonprofit organization dedicated to promoting education in molecular biology for both children and adults. We work inside and outside of traditional settings, providing a safe, supportive environment for training and mentoring in biotechnology.

6. Kwok, Roberta (2010) “Five hard truths for synthetic biology.” Nature Vol. 463, pp. 288-290. (HTML) (PDF) “Can engineering approaches tame the complexity of living systems? Roberta Kwok explores five challenges for the field and how they might be resolved.

HowPlantsWork © 2008-2011 All Rights Reserved.

joker-card-01.jpgHow To Screw Organic Farmers

In a recent issue of our local paper, there was a tragic story about how several organic farmers in the region had unknowingly purchased manure which turned out to be contaminated with a powerful herbicide. Consequently, they lost most of their crops. And they certainly lost their organic seal of approval.

How did this happen? And how common is it for organic growers to be screwed in this way?

This story led me to investigate instances of herbicide contamination in so-called “organic” manure.

It turns out that instances of this problem have been reported for several years. Cases were well documented in England in 2008 and 2009. ( Map of contaminated manure UK 2008/2009 ) Indeed, the herbicide in question was banned in the UK, at least, for time. (UK ban petition) It was reinstated in April, 2010.

Here’s the story.

As described in a previous posting, many herbicides work by interfering with the plant hormone auxin. These so-called auxinic herbicides have been around for long time. So long that some plant species targeted by these herbicides have developed resistance to them.

Chemical companies such as Dow Chemical have overcome this resistance by making chemical modifications to these herbicides in order to create new versions. An example of this is the herbicide aminopyralid.

This herbicide was introduced several years ago and is proven to be a problem because of its resistance to biological breakdown. It persists in hay, manure, compost, and grass clippings (also, see refs below).

From the makers of this product: DOW Agrosciences UK and DOW Agrosciences USA

Does your manure contain herbicides?

Bioassay for herbicides in manure – Mother Earth News

And, finally, a personal story – Persephone Farms.


1. Aminopyralid Residues in Compost and other Organic Amendments – Whatcom County Extension

2. Persistent Pesticide As Organics Recycling Foe

3. Davis, J., S.E. Johnson, and K. Jennings (2010) “Herbicide Carryover in Hay, Manure, Compost, and Grass Clippings: Caution to Hay Producers, Livestock Owners, Farmers, and Home Gardeners”, North Carolina Cooperative Extension. (PDF)

4. Aminopyralid Family of Herbicides, Dow AgroSciences (2010) (PDF)

HowPlantsWork © 2008-2011 All Rights Reserved.

Can Chemically Inducing Dormancy Help Plants Cope With Stress?

sleepyhead.jpgThis was a very bad year for wheat in Russia because of an extraordinarily hot and dry summer. And many climatologists believe this may be only a glimpse of the not-too-distant future in many parts of the world. If so, then it is of critical importance to find ways to make crop plants more drought and heat tolerant.

One way to do this, of course, is to develop new varieties of crops that can better withstand hot, dry summers. Unfortunately, using conventional plant breeding, this typically takes a very long time, sometimes decades.

But what if it was possible to spray plants with a chemical that induces them to become more tolerant of heat and drought?

Some scientists believe that research reported in the last couple of years have brought us steps closer to such a scenario.

Abscisic Acid = The Plant’s “Sleeping Pill”?

green_pills.jpgAs mentioned in a previous post, the plant hormone Abscisic Acid (ABA) triggers the closing of stomata in plant leaves in response to water stress. It also is well known in promoting dormancy in seeds of many plant species. (ABA may also play a role in maintaining a state of dormancy in other parts of plants, but scientific evidence for this is equivocal.)

In a way, plant dormancy is somewhat analogous to sleep in that it may induce a sort of near inactive metabolic state in plants.

In such a state, plant cells and tissues are usually better able to withstand extremes of cold, heat, and drought. Briefly, this is due to the expression of protective proteins, such as dehydrins, and to changes in the cellular structures, such as the composition of cell membranes.

What ABA does is trigger the cellular processes involved in such changes. The question that has confounded scientists for many years is exactly how ABA does this.

Targets and messengers.

It turns out that 2009 and 2010 have been very good years for research on the mode of action of the plant hormone ABA.

In 2009, several laboratories, including Sean Cutler’s lab at UC Riverside, identified ABA receptors, that is, cellular proteins that specifically bind to ABA.

And this year, much more was learned about the docking site for ABA on these proteins and about what these proteins do. (See here and here for more about this.)

Briefly, these proteins function as phosphatases, which often function to regulate the activity of other enzymes. In this way, they act as an army of messengers, greatly amplifying and elaborating the ABA signal.

Artificially Inducing Dormancy?

Information about the ABA docking site may allow scientists to develop chemicals, such as pyrabactin, that can mimic the action of ABA, but that are way more stable and cheaper than the natural plant hormone ABA itself.
Some scientists envision the use of such chemicals as a way to artificially induce a transient dormancy-like state in growing crop plants, such as wheat for example, in order for them to survive episodes of extreme heat and drought.

For example, Dr. Mike Sussman, from a recent article regarding his work on ABA puts it this way: “”Since they cannot walk or run, plants have developed an interesting and complicated system for sensing and responding very quickly to dehydration and other stresses,” says Sussman, noting that, on average, a plant is composed of 95 percent water. “Most plants have what’s called a permanent wilting point, where if water content goes below 90 percent or so, they don’t just dehydrate and go dormant, they dehydrate and die.”

Figuring out how to trigger a dormant state, such as exists naturally in seeds, which are 10 percent water and can in some cases remain viable for hundreds of years, could be key to creating plants that survive drought in the field, Sussman explains.

It’s possible that someday farmers will spray their wheat fields with such chemicals, which will induce the plants to “sleep through” an unusually hot, dry period.

HowPlantsWork © 2008-2011 All Rights Reserved.

garden.jpgYES! Here’s How (And Why):

Although “Global Warming” is to some people a controversial subject, the one thing that’s not controversial is that the level of atmospheric CO2 has significantly increased in the past 100 years and will likely continue to increase – at least until humans stop burning fossil fuels. (We’ve previously visited this subject on a number of occasions, here and here, for example.)

OK, so atmospheric CO2 is at historically very high levels and is going even higher in the decades to come. How will this likely affect plants?

As previously discussed, since green plants use CO2 as the carbon source in photosynthesis, they will probably do more photosynthesis, i.e., produce more biomass.

But as is often the case with things biological, it’s not quite as simple as that.

Fertilize More, Water Less

For your garden plants to take full advantage of this high CO2 world, you will probably need to add more nitrogen fertilizer, but you may have to water less often. Here’s why.

For optimal plant growth, plants need sufficient amounts of carbon and nitrogen and water.

In a high CO2 world, plants will have a sufficient carbon source. But if the availability of nitrogen is limited, then plant growth will be limited. Therefore, to fully take advantage of a high CO2 world, your garden plants will need to have sufficient amounts of nitrogen (N). In most cases, nitrogen is available to plants in the form of nitrate (NO3) in the soil. So to ensure your plants thrive in a high CO2 world, add plenty of compost or nitrogen-containing fertilizer.

Plants in a high CO2 world will also use water more efficiently. This is because the stomates in the leaves need to open less to obtain sufficient amounts of CO2. This is good, because then the plant transpires less water. The result, in general, is that plants will use less water for a given amount of biomass production in a high CO2 world.

corn.jpgDon’t Plant Corn

Not all plants will benefit from a high CO2 world.

So-called C-4 plants already use CO2 very efficiently. Consequently, their photosynthesis will not be significantly improved with increased amounts of atmospheric CO2.

Corn or maize is a classic C-4 plant.

Other C-4 plants include sugarcane, sorghum, and so-called ”warm season” grasses.

Other cereals such as wheat, barley and oats are not C-4 plants — they are so-called C-3 plants — and should benefit from a high CO2 world.

Bottom line: People on this planet show no signs of throttling back their use of fossil fuels. On the contrary, the production of CO2 from the burning of fossil fuels, especially coal, will likely increase in the coming years.

So, it makes sense to prepare for a high CO2 (and probably warmer) world by learning more about how plants will likely respond to such changes in their environment.

HowPlantsWork © 2008-2011 All Rights Reserved.

And The Winner Is……….

At the beginning of this series, I wondered if the impressive array of sensors in the new iPhone rendered it “smarter” than the average plant, at least when it came to sensing and responding to its surroundings.

A summary of my comparison is shown in the table below.


Briefly, the iPhone has at least one sensor – the magnetometer – that plants don’t have. (Despite all the reports of geomagnetic effects on plants over the years, few, if any, are truly repeatable, and, thus, credible. Please see here for more information.)

Also, one could argue that plants lack a true 3-axis gyroscope.

Therefore, it would appear that the iPhone has more types of sensors than plants.

However, when it come to light-sensors, plants clearly have the advantage. Most flowering plants have at least three different photoreceptors – phytochromes, cryptochromes, and phototropins. (And I’m not even counting pigments such as chlorophyll and carotenes.)

These photoreceptors work by affecting a complex array of biochemical and genetic pathways inside plant cells. Consequently, most plants have the ability to respond in very complex ways to even subtle changes in the quantity and quality of light in their environment.

Plants also have sensitive mechanical and gravity sensors that allow them to alter their development in response to these environmental cues. Again, by affecting complex cellular mechanisms, these gravi- and mechano-sensors are able to elicit sophisticated environmental responses by the plants.


marigold_twining.jpgThough the iPhone 4 may have a couple of environmental sensors lacking in plants, plants are much more intelligent than iPhones when it comes to how they respond to their surroundings. That is, plants display a much higher level of complexity in their responses to signals from their sensors.

Plants can not only alter their functions in response to light, for instance, but also can actually change their form to adapt to changes in their environment.

Therefore, though iPhones may be able to sense more things in their environment (magnetic “north”, for example), plants respond to their surroundings more intelligently.

(Even though most dogs have a better sense of smell than you do, and cats have better night vision, you’d probably not say that they are more intelligent than you are.)

Bottom line: Though they might not sense the environment in as many ways or as well as some inanimate objects, such as an iPhone, plants – as with most lifeforms – are much more intelligent when it comes to responding to changes in their environments.

HowPlantsWork © 2008-2011 All Rights Reserved.