The researchers have demonstrated that under the right growth conditions woad (Isatis tinctoria) produces astonishing amounts of glucobrassicin (GBS), a biochemical which may account for some of the cancer-fighting properties of related plants, such as broccoli.

“It can make more than 60 times the amount found in broccoli, and in a much purer form,” says Stefania Galletti at the Experimental Institute for Industrial Crops in Bologna, who carried out the study with colleagues at the University of Bologna in Italy.

Glucobrassicin is a natural component of broccoli, cabbage and other members of the Brassicaceae plant family. It is a highly reactive chemical and at least one of its by-products, indole-3-carbonyl, is a well known tumour-busting compound.

But the exact fate of GBS in the diet has been difficult to determine because such studies would require large samples of the pure compound and it is difficult and expensive to purify or synthesise.

“Bug” damage

Although woad is a Brassicaceae member and was known to contain GBS, it was not an obvious source of the chemical. “Until recently, it had almost disappeared from cultivation,” says Galletti. For thousands of years, woad had been treasured as a source of blue dye, but in the past century it was displaced by less expensive dyes, such as indigo.

Examining different cultivated varieties, Galletti’s team found one woad stock that was not only rich in GBS, but also had low levels of related chemicals, which would make purification far easier. The researchers then looked for ways to further boost the chemical’s concentration.

They treated the plants with nitrogen and sulphur fertilisers, since the GBS molecule contains both atoms. And because GBS is produced by plants as part of a natural insecticide system, they also wounded the plants with abrasive powder or a brass brush to simulate bug damage.

Crop rotation

The result was nearly a four-fold boost in production over undamaged control plants that received no fertiliser, so that more than 1% of the plant’s dry weight became GBS. Both treatments are cheap enough to apply at an industrial scale.

For researchers, this may mean that they finally get their hands on enough GBS to nail down the details of its metabolism and anti-cancer properties.

And for woad farmers it means another potential market. “They can rotate their crops,” says Galletti. “One for the dye, one for the lab.”

Journal reference: Journal of the Science of Food and Agriculture (DOI: 10.1002/jsfa.2571)

Embryonic stem cells (ESCs) are an attractive source of human T-cells for research and therapy because ESCs can be genetically manipulated with relative ease and can be grown in large quantities.

T-cells are crucial to the working of the immune system. If these cells are destroyed or absent – as occurs during HIV infection and X-SCID, respectively – the body cannot fight off infections. But despite their importance, much about human T-cell function is unknown because the cells are difficult to analyse with standard tools of genetic engineering.

“Introducing new genes is inefficient in T-cells and can activate the cells in inappropriate ways,” says Jerome Zack at the David Geffen School of Medicine at the University of California, Los Angeles, US.

Three-step process

Instead, Zack’s team genetically-engineered ESCs and then pushed them to become T-cells in a three-step process. First the cells were given a gene for a green fluorescent protein using a genetically-engineered virus. Next, the cells were grown on mouse bone marrow cells. Finally, they were injected into a small piece of human thymus which had been implanted in a mouse with a deficient immune system.

The bone marrow and thymus are known to provide chemical factors necessary for normal T-cell development. In the end, as many as 24% of the T-cells in the implanted thymus proved to have derived from the green fluorescent ESCs – the rest were produced by the thymus from progenitor cells supplied by a small piece of human liver that was part of the transplant.

The technique opens many possibilities. For genetic diseases, like X-SCID – a severe immunodeficiency, often fatal in the early years of life – ESCs derived from the patient could be given a functional version of the defective T-cell gene. For HIV, ESCs could be engineered to inactivate the gene for CCR5, a surface molecule that the virus needs to successfully attack T-cells.

Key player

However, the future of all ESC-based therapy remains uncertain as it is not yet known if ESCs can be immunologically matched to a patient by therapeutic cloning or by selecting a match from a large bank of different ESCs (see After the hype: What Dolly the sheep really did for us).

“This is certainly not ready for prime time in the clinic,” Zack says. Robert Lanza of Advanced Cell Technology based in Alameda, California, US, says the work “lays the foundation for the potential future treatment of various blood disorders”.

For now, Zack’s team is eager to exploit the new technique to better understand the T-cell, a key player in the human immune system.

Amy Wagers, a stem cell biologist at Harvard Medical School in Boston, Massachusetts, US, says that alone would be an important advance. “In the near term, this gives you a much more versatile model system to study human T-cells.”

Journal reference: Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.0604244103)

Teruhiko Wakayama of the Rockefeller University in New York and his team say the mice in their experiment appeared healthy. But it became harder to clone them with each successive generation.

Only one mouse was produced in the sixth generation despite massive effort. And this lone clone was eaten by its foster mother. “Either it was sick and died or the foster mother didn’t like it and destroyed it,” he says.

Cloning is based on a technique known as nuclear transfer. The nucleus of a donor cell is fused with an egg stripped of its own genetic material. The result is an animal that is genetically identical to the animal from which the donated nucleus came.

Wakayama and his team first hit the headlines two years ago when they cloned the mouse Cumulina, the first clone produced from an adult animal since Dolly the sheep.

They also announced the remarkable feat of serial cloning. By using donor cells from each successive generation, they produced four generations of clones. In their new report, they report for the first time that they could not produce mice past the sixth generation.

They explored two possible reasons. First, the end of chromosomes or “telomeres” have been seen to shorten in some cloned animals. This erosion could make viable offspring impossible after serial cloning. Secondly, they suspected that the general health of the clones might deteriorate with each set of new offspring.

But neither one of these possibilities seems to be true. In fact, the mouse telomeres seem to grow slightly with each generation. And all the clones could navigate mazes and pass other cognitive tests with flying colours. They also aged gracefully – one fifth generation mouse is alive and well in mouse middle age, 18 months.

Wakayama’s team continues to search for some hidden flaw. “Our results suggest clones are accumulating some abnormality,” he says. The fact that the final animal was eaten by its foster mother might suggest the defect is obvious to rodent senses, if not human testing.

Source: Nature (vol 407, p 318)

Or take the once notorious American Lenape—or rather, don’t. All seemed
well with this hardy new variety of potato launched in the US and Canada in the
1960s. Then came the bitter truth. Biochemists discovered the source of the
tuber’s unusual burning flavour: dangerous levels of toxins called
glycoalkaloids.

“Many nightmares predicted for genetically engineered crops have already
happened,” reflects Tony Conner of the New Zealand Institute for Crop and Food
Research near Christchurch. It’s just that “not many people noticed or cared”
because they were the fruits of conventional breeding, not genetic
manipulation.

In fact, many biotech insiders and government food regulators, especially in
the US, believe that the public has got it all wrong. By the time a “gene food”
reaches people’s plates it is not merely as safe as a conventional food—in
some respects it is actually safer, because of the intensive testing that
regulators demand for high-tech food crops. By the end of this year millions of
Americans will have eaten these foods, says Arnold Foudin of the US Department
of Agriculture in Beltsville, Maryland. “And yet you won’t be seeing anyone
dying in the street.”

Frankenfoods

However, you won’t be seeing opponents of gene foods downing their placards,
either. In Europe especially, campaigners have been working flat out in recent
months to prevent genetically engineered crops being grown on the same scale as
in North America. Their tactic has been to play the moral/emotional card for all
it’s worth and brand all genetically engineered crops “Frankenfoods” regardless
of the specifics of each genetic modification. So far, it has worked amazingly
well. All hell broke loose in Britain in August when a food scientist appeared
on TV claiming—wrongly as it turned out—that a potato he’d
engineered was toxic to rats.

Inevitably, the questions that really matter have vanished amid the confusion
and theatre. How do specific genes and the proteins they encode behave in the
body? Do the types of genes and proteins being introduced into high-tech crops
raise any new threats to food safety that could go undetected by researchers in
companies or government labs? The answers reveal that the biotech industry is on
solid ground when it claims its products are no riskier than conventional foods.
But it strays into some distinctly swampy territory when it claims, as it
continues to with some force in the US, that genetically engineered foods need
not be routinely labelled.

First, there is the issue of food safety. In traditional breeding, scientists
often introduce unknown genes into a plant species en masse by hybridising them
with a related species with a desirable trait. Genetic engineering, by contrast,
involves splicing no more than a few well characterised genes into a plant. That
seems less drastic but can still produce unforeseen effects. In either case, the
influx of new DNA might end up in critical parts of the genome, altering the
behaviour of the plant’s normal complement of genes, slashing the production of
nutrients or pumping up the level of natural toxins. In many species, plant
biochemistry is not just complex and sensitive, it’s actually geared up for
producing toxins to ward off predators—hence the bitter Lenape and toxic
celery.

“That’s why it’s standard to thoroughly analyse these new transgenic plants,”
says Roy Fuchs of Monsanto in St Louis, Missouri. “We need to see that they are
substantially equivalent to commercial plants.” To that end, Fuchs and his team
run each promising transgenic crop through a battery of biochemical checks. They
monitor levels of nutrients, proteins and potential poisons, and, in some cases,
feed the crop to livestock to check that the animals gain weight at the normal
rate and remain generally healthy.

But what about more insidious effects? Some people worry that genetic
engineering brings new DNA into the food supply, from microbes, for example.
Couldn’t this new DNA end up invading our genomes or the genomes of our gut
bacteria? Few scientists take this threat seriously. Not even Walter Doerfler, a
researcher at the University of Cologne in Germany, whose work has been seized
on by opponents of gene foods.

Last year, Doerfler’s team found that when DNA from a bacterial virus was
eaten by a mouse, some snippets of viral genes invaded the animal’s bloodstream
and cells—and, on rare occasions, even linked itself to mouse DNA (New
żěè¶ĚĘÓƵ, 4 January 1997, p 14; Proceedings of the National Academy of
Sciences94 p 961)). “This generated a lot of hysteria in the genetically
engineered food arena,” remembers Doerfler. But he believes that mammals have
defences against this genetic onslaught. In his experiments, the vast majority
of the viral chromosomes were shattered into pieces too small to contain intact
genes. And despite scouring tissues throughout the mouse, Doerfler has never
found any evidence of active ingested genes—even ones designed to work in
human cells.

Shredded genes

Nor are microbes in the human gut likely to pick up genes from food. Most DNA
from food will be destroyed well before it reaches the bacteria, with any
surviving remnants being shredded again inside the bacteria by so-called
restriction enzymes. Even if intact genes were to successfully invade a
bacterium or human cell, they’re unlikely to spring into action because their
activity will be controlled by DNA switches designed to work only in plants.

The one exception may turn out to be the antibiotic resistance genes that
biotechnologists routinely use as “markers” for handling DNA in bacteria and
identifying its presence in plant cells. Despite all the scare stories about
these marker genes, those in crops now approved for commercial growth have been
genetically scrambled, so there is little chance for their resurrection, or they
are of no clinical importance. So it’s unlikely that these particular genes
could boost the spread of antibiotic resistance in human pathogens. Even so,
critics worry that there is nothing to prevent scientists from using different
markers in future, and while scientists agree that the chance of one of these
genes jumping from food into a new cell is tiny, few will say it is
impossible.

Technology could soon make it impossible, however. Some years ago, David Ow
and his colleagues at the Plant Gene Expression Center in Albany,
California—a lab belonging to the US Department of
Agriculture—discovered a way of removing marker genes and other extraneous
DNA from engineered plant cells. Their approach involved using a pair of
molecular scissors called CRE, an enzyme from a bacterial virus, to snip out the
antibiotic resistance DNA. Since then, Ow’s group has shown the same editing
trick also works in an important food crop, wheat.

Until now, industry researchers have shown little interest in the work
because they insisted that their genes posed no threat. But attitudes seem to be
changing. “There is no clinical concern here whatsoever,” says Jeff Stein of
Novartis in Greensboro, North Carolina. “But we do worry about public
perception.” While not disclosing too many technical details, Stein says that
all future Novartis crop products will be “100 per cent” free of antibiotic
resistance genes. Other companies are also investigating ways of cutting out
antibiotic resistance genes and surplus DNA.

More recently, Ow’s team showed that the editing process can run in reverse,
enabling researchers to insert foreign genes into plant chromosomes at exact
locations (Plant Journal, vol 7, p 649)—something that has so far
been impossible. The method involves the insertion of DNA “docking sites” into
unimportant areas of a chromosome. In future, researchers will be able to use
such sites to slot new genes into plants without disturbing their normal
complement of genes. Genetic engineering will finally become the precision tool
that the biotech industry claims it to be.

Not that this would deal with every worry. In some cases, the transgenic
protein encoded by this precision-engineered DNA might itself turn out to be
toxic, although detecting this wouldn’t be a problem. Unlike conventional
breeders, biotechnologists can use the genes that interest them to produce
transgenic proteins in bacteria to test on animals.

A more subtle effect of proteins is harder to deal with. When molecular
biologists shuttle new genes into plants, they might inadvertently introduce
proteins capable of triggering respiratory or inflammatory problems in the one
to two per cent of people who suffer from food allergies. żěè¶ĚĘÓƵs at
Iowa-based Pioneer Hi-bred, one of the world’s largest seed companies, learnt
this the hard way. In the early 1990s, its researchers engineered a more
nutritious strain of soya bean by adding a gene taken from brazil nuts. The gene
encoded a protein rich in methionine, a nutrient that is in short supply in
ordinary soya beans. At the company’s request, allergy specialist Steve Taylor
of the University of Nebraska in Lincoln studied antibodies and immune responses
from patients allergic to brazil nuts. Pioneer Hi-bred dropped the soya bean
project when Taylor discovered that the hybrid was likely to trigger a major
attack in people with brazil nut allergies.

To some, it seemed like a narrowly averted disaster. After all, research
based on animal experiments published only a few years earlier suggested that
the same protein was not an allergen. “Allergy science is in its infancy,” says
Jane Rissler, a plant pathologist with the Union of Concerned żěè¶ĚĘÓƵs in
Washington DC. “That’s a good reason to collect a lot more data before doing
these widespread transgenic releases.” Taylor himself extracts a different
lesson. “It shows you can’t be cavalier about allergies,” he says. “But it also
shows the system is working.”

The system he refers to is a series of tests that scientists now use to flush
out allergens before they are put into crops. If the transgenic protein comes
from a known allergenic food, it is subjected to immunological tests. If the
protein comes from other sources, researchers study its molecular structure
(amino acid sequence), looking for similarities with allergy-triggering proteins
in the databases. The protein’s chemical hardiness is also scrutinised. In
test-tube simulations of the heat, acid and enzymes found in the stomach, most
proteins are torn to shreds in seconds. Allergens tend to survive several
minutes before they, too, are destroyed.

Mystery ingredients

Even if true allergens do escape detection and make it into transgenic crops,
immunologist Yueh-hsui Chien of Stanford University questions whether this
represents a new risk to the consumer. “If you regularly eat tomatoes, and then
you eat a transgenic one, you know you are eating a few new proteins,” she says.
“The first time you eat a lobster, you eat several thousand new proteins.”

But that’s a false comparison, argues Rebecca Goldburg, senior scientist at
the Environmental Defense Fund, an advocacy group in New York. She points out
that someone knows they are eating a lobster. But the new ingredient in the
tomato is invisible because transgenic crops are, for the most part, unlabelled
and mixed in with the rest of the harvest. “The industry is depriving us of one
of our most important natural defence mechanisms,” she says. “Reading
ľ±˛Ô˛µ°ů±đ»ĺľ±±đ˛ÔłŮ˛ő.”

In the US, companies argue that the chance of allergic responses to the
current generation of modified crops is too remote to warrant segregation and
labelling. And so far, the US Food and Drug Administration has supported this
view by introducing rules that require farmers and manufacturers to segregate
and label transgenic foods only if there is good reason to suspect they might
behave differently in the body than more conventional foods. Officials in Europe
made a similar ruling in September, but in Britain and many other countries in
the European Union, some manufacturers and retailers have decided to label
products voluntarily.

Full disclosure may soon be a major fashion. In the industry, the most
excited talk is about using molecular biology to lower undesirable chemicals or
boost nutrients in food. At Nagoya University in Japan, for example, researchers
have managed to slash levels of the major allergenic protein in rice by 70 to 80
per cent by inserting a so-called antisense gene to block the protein’s
production in the plant.

If biotechnology dramatically increases the quality or safety of food,
companies on both sides of the Atlantic may soon be falling over each other to
market new and improved gene crops—and to provide the public with more
information about what they are eating.

Then we can decide for ourselves which of the risks—low tech or high
tech —we are willing to take when we eat our next meal.

Jeff Turner, president of Nexia Biotechnologies, says the biodegradable
fabric would need to be sealed from the environment if used in critical
applications such as body armour or spacecraft. This is because bacteria could
get in and digest it.

Turner’s team has already taken the first step towards creating biosteel by
transferring the spider gene for the protein into goat mammary cells and
collecting soluble protein from the milk. And they expect genetically engineered
goats to start producing the protein in the next few months.

While nobody has yet made a fabric from biosteel, Turner is convinced the
protein can be turned into a supermaterial because of its natural role in the
silk of a spider’s web. “When you think of what a web has to do, its extreme
strength makes perfect sense,” he says. The silken threads of the web must be
nearly invisible to prey and yet be able to bring a fly to a screeching
halt.

Evolution came up with a two-pronged answer to this problem. First came a
rock-solid protein, capable of making many bonds with its neighbours. Then, the
spider developed a unique way of spinning the protein into a whisper-thin
thread. As the spider secretes the protein solution, the silk dries and pulls
taut, transforming the proteins into a nearly crystalline and completely
insoluble cable. This explains why webs don’t dissolve in the rain. Tests on
natural silk show that it can be stronger and more elastic than high-tensile
steel or the Kevlar found in body armour.

But the very properties that make silk proteins strong also make them
difficult to produce. When bacteria are engineered to produce large quantities
of the protein, for example, it links up in chains into a disordered, insoluble
mess. Its ability to bond with its neighbours can happen in a very ordered or a
disordered fashion—depending upon how the proteins fold as they form.
Which is why Turner and his colleagues decided to mimic the spider’s own method
of production by using goat mammary cells. It turns out that the way mammals
produce milk proteins and spiders make silk proteins are broadly similar. Both
are produced in skin-like epithelial cells, then held in a space, or lumen,
where shear stresses on the protein are minimised.

So far so good. But Turner cautions that the work is still in its early
stages. It will take about a year before the herd of biosteel goats is large
enough for Nexia’s scientists to collect the protein they need to start making
fabric. Then they will face the next great hurdle: how to match the spider’s
spinning skill. “Nature probably took a long time to get this process right,” he
says. “I suspect the same will be true for us.”

OLD-FASHIONED film cameras are better at catching bank robbers than modern
video cameras, according to an FBI report presented at the American Academy of
Forensic Sciences. Bureau scientists say video cameras can be useless for
identifying criminals.

In the early days of surveillance, banks had hidden film cameras that were
triggered by staff during a crime and snapped photos every few seconds. But in
the 1970s, many banks switched to video cameras, believing that it was important
to be able to monitor an area continuously—and to cut the cost of using
film.

Now most banks use video. “We’re seeing so much more video than we do film,”
says Thomas Musheno, a forensic scientist at the FBI laboratory in Washington
DC. The problem, he explains, is that the FBI usually uses tiny details they
call “unique identifying characteristics”, such as scars or moles, to identify a
criminal.

In close-up, video can capture these features as well as film. But cameras
are often mounted 6 metres from tellers. At that distance, an image of a
gunman’s face can be decidedly uninformative. “You can hardly tell it’s human,”
says Musheno.

The cameras normally record a picture field once a second—making a
2-hour tape last for 72 hours. Only every second line of the 480 lines on the
screen is recorded in each field. So if a distinctive wart or scar lies in the
odd lines, the police are out of luck.