Barking up the right GM tree?

Although genetically modified crops such as cereals and cotton continue to attract much scientific and political attention, there has been little debate about the large worldwide research effort to develop GM trees.

Trees with foreign genes added have grown in 700 field trials in at least 21 countries over the past 20 years, says Matthias Fladung of the Thünen Institute of Forest Genetics in Germany. They include dozens of deciduous and coniferous species, with most work done on eucalyptus and poplar.

GM poplar, engineered to make a natural insecticide (Bt toxin) in its leaves, is already grown on a commercial scale in China. “There is no independent assessment of transgenic poplar in China,” says Rick Meilan, who works on poplar at Purdue University in the US. “The area planted may cover thousands of hectares.”

Meanwhile, two biotechnology companies, FuturaGene and ArborGen, are leading the effort to commercialise GM eucalyptus in Brazil and the US.

Some of the reasons for forestry researchers wanting to grow GM trees are similar to those motivating agricultural scientists, such as pest resistance and survival in adverse conditions such as drought or cold.

Others are more particular to trees, such as altering the amount of lignin in their trunk and branches to make the wood easier to process for paper or biofuel – or simply to produce timber more quickly.

GM trees also pose environmental concerns similar to those of GM crops – and sometimes in heightened form. The European Union is assessing these risks in a wide-ranging research programme outlined at last week’s Euroscience Open Forum conference in Dublin.

Because trees grow so tall, they disperse their pollen over a wider area than cereals. They live for decades, so any harmful effects will persist for far longer.

But the most important point is that trees in commercial plantations are genetically far closer to their wild forest relatives than farm crops, which have been altered extensively by centuries of breeding. Unless modification also makes the trees sterile, there is likely to be little barrier to hybridisation between GM and non-GM trees of the same species.

Supporters of the technology say that genetic modification is needed for trees, even more than for farm crops, to short-circuit the breeding process and generate traits that cannot be introduced conventionally. Fast-growing GM poplar and eucalyptus could provide timber or biofuels while removing carbon dioxide more effectively than conventional trees.

“Trees are ‘wild’ plants, at least in comparison with most crop cultivars,” Fladung says. “Genetic engineering offers a fast way to domesticate them.”

Gut reactions: a mixed diet is key to health

Scientists are gathering more and more evidence to show the importance to human health of the billions of bacteria living in our guts.

The latest research from Ireland was revealed at last week’s Euroscience conference. Scientists at University College Cork found a strong correlation between the health of elderly people and the diversity of microbes in their intestines – the “gut microbiota”.

Their study of 178 people with an average age of 78, living in their own homes and long-term residential care, showed that a greater variety of gut microbes was associated with less frailty and better health. (Results were adjusted for gender, age and location.)

The microbiota of people in care was generally much less diverse than those living at home or with family. The reason for a less diverse microbiota was a less varied diet, the research showed. The paper will appear in the journal Nature.

“We had observed previously that the gut biota is more variable in older people than in younger people,” says Paul O’Toole, senior author. “Now we have shown that the variations are driven by an individual’s diet.”

The reason seems to be that a more varied diet can support a wider range of microbes – and these bacteria help the gut to extract more nutrients from the food.

Bacteria even make biological molecules similar to human neuro-transmitters (brain chemicals), O’Toole says: “It is possible that having an active and diverse microbiota can improve cognitive activity in the elderly.”

The total number of bacteria in a healthy adult is estimated to be 10 times greater than the number of human cells.

People may be able to boost the population of some species of gut bacteria by eating “probiotic” foods; but the only way to maintain maximum diversity is through a varied diet.

Birds of a feather, quiet together

Baby sparrows need to be heard

Urban noise is loud enough to interfere with communications between nesting birds and their chicks, according to scientists at the University of Sheffield. This may contribute to the decline of some species in towns and cities, they say.

The researchers carried out their study, not in an urban environment, but on the population of house sparrows living on the island of Lundy in the Bristol Channel. The setting was ideal for the purpose because Lundy does not have a power grid and produces electricity on-site with the help of noisy generators.

The study, published in the journal PLoS One, compared sparrows nesting in a barn next to a generator with birds breeding in quiet barns and elsewhere on the island. Eggs were swapped between nests to eliminate any genetic effects.

“Chicks that were reared in the noisy barn were lighter when they fledged,” says Julia Schroeder, lead author. “Their mothers did not feed them as often as in quiet places and they survived less well. When the noise was turned off, the broods in the noisier areas were fed more often.”

Sparrow populations have fallen steeply in London and other cities. The Sheffield scientists believe one reason may be that parents are less able to hear their chicks calling for food. “We believe that the noise from the generators on Lundy is comparable to the one made by cars [and urban activity] in cities,” Schroeder says.

Fish catch love bug from pollution

High levels of bisphenol A (BPA), an environmental pollutant that mimics the effects of hormones, may blur the barriers between fish species and lead to interbreeding, a US study has shown.

Jessica Ward from the University of Minnesota and Michael Blum of Tulane University investigated the effect of BPA on two closely related species of river fish, the blacktail shiner and red shiner.

They kept the shiners of each species for two weeks in separate tanks, some containing BPA in the water and some not. Then males and females from the two species were introduced to each other.

The fish that had been bathed in BPA were much more likely to show sexual interest in the other species than those from pure water tanks.

Their mating behaviour changed because the BPA, by mimicking the effects of oestrogen, reduced differences in appearance. The researchers say this could have long-term ecological effects, especially in areas threatened by invasive species.

“Our research shows how the presence of these man-made chemicals leads to a greater likelihood of hybridisation between species,” says Ward. “This can have severe ecological and evolutionary consequences, including the potential for the decline of our native species.”

But other scientists point out that the BPA concentrations used in the experiment were much higher than those found in the environment. “In the wild, such levels of bisphenol A would never occur unless there was a spillage,” says Richard Sharpe of the University of Edinburgh.

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