A three-year field trial in Norfolk of potatoes genetically modified to resist late blight – the fungal disease responsible for the great Irish famine of the 19th century – has produced encouraging results.
Plants with a resistance gene inserted from a South American wild relative of potatoes remained free of infection, while all the non-GM potatoes succumbed to blight. The results were published on Monday in the journal Philosophical Transactions of the Royal Society B.
The trial, led by Jonathan Jones of the Sainsbury Laboratory in Norwich, used Desiree potatoes, one of the most popular varieties in the UK. Each year 192 GM potatoes were planted, alongside non-GM control plants, on the trial plot.
Blight remains the most serious hazard for potato growers. According to the researchers, it causes £3.5bn of worldwide losses annually and costs British farmers £60m to control in an average year. Potato crops are typically sprayed 10 to 15 times per season – and up to 25 times in a bad year.
The introduced gene triggers the plant’s natural defence mechanisms, enabling it to recognise and fight the fungus. Although breeders have attempted to introduce blight-resistant genes by conventional methods, this has not worked well, says Jones. “Breeding from wild relatives is laborious and slow, and by the time a gene is successfully introduced into a cultivated variety, the late blight pathogen may already have evolved the ability to overcome it,” he says. “With new insights into both the pathogen and its potato host, we can use GM technology to tip the evolutionary balance in favour of potatoes and against late blight.”
The trial was funded mainly by a £750,000 grant from the Biotechnology and Biological Sciences Research Council. In addition BBSRC spent £46,000 to secure the field site against anti-GM campaigners.
The next step in the project will be to identify two other resistance genes which can be added to GM potatoes to give triple protection. It would be very hard for blight to evolve resistance to all three at the same time, according to Jones. This will be done in collaboration with Simplot, a privately owned US food and farming company based in Idaho.
BASF, the German agrichemical group, has developed a GM potato – called Fortuna – with two blight-resistant genes. But the company decided last year that, in view of Europe’s strong anti-GM movement and burdensome regulations, the costs and obstacles of bringing Fortuna to market in the region were too high to justify further investment in the project.
Breast milk’s very own gender-based formula
Mothers of mammals (including humans) treat boys and girls differently from the very beginning, even adjusting the composition of their breast milk according to the sex of their offspring.
Katie Hinde, an evolutionary biologist at Harvard University and a pioneer of milk composition research, says there could be important implications for nursing mothers and for the way formula milk is made.
“We think it’s important – [when] it’s not – to make different deodorants for men and women, and yet we approach formula milk as though boys and girls have the same developmental priorities,” Hinde told the American Association for the Advancement of Science meeting in Chicago this week.
The amounts of key nutrients vary according to the sex of the offspring. Milk for boys – particularly firstborns – tends to be richer in fat and protein, while milk for girls contains more calcium.
Hinde is most interested in cortisol, a metabolic hormone found in real milk but not in formula. Her research uses rhesus macaques, which tend to produce more cortisol for sons than daughters.
She found that variations in the amount of cortisol in the monkeys’ milk affected the emotional development of offspring in different ways. Although some of the hormone is beneficial, female babies became more nervous if the total amount of cortisol in their mothers’ milk was high. Male babies were less sensitive to the overall level of cortisol but more sensitive to the way it changed with time: the ideal was for it to start high and decline during lactation.
The findings support the idea that “breast is best”. However, when maternal milk is unavailable, the research suggests that the composition of formula could be adjusted according to the sex of the baby. “We have good reason to be sceptical of one size fits all for formula,” Hinde says.
Shivering could help with weight loss
Shivering in the cold is as effective as moderate exercise at converting the body’s energy-storing “white fat” into healthier energy-burning “brown fat”, US research has shown.
The study, carried out by the National Institutes of Health, lends support to the idea that periodic exposure to the cold could help people fight obesity and associated diseases such as type 2 diabetes.
“White fat transformation into brown fat could protect … against diabetes, obesity and fatty liver,” says Paul Lee, lead author of the study, which is published in the journal Cell Metabolism. “Glucose levels are lower in humans with more brown fat.”
The researchers discovered how two specific hormones enable fat and muscle cells to communicate in the process that turns white fat into brown. Brown fat stores energy in a form that the body can burn relatively quickly to provide warmth or power exercise. White fat is a much longer term energy store.
Babies are born with a store of brown fat around their necks. Most of this vanishes during infancy but adults retain some brown fat – and people who have more of it tend to be slimmer.
“When we are cold, we first activate our brown fat because it burns energy and releases heat to protect us,” says Lee, who now works at the Garvan Institute of Medical Research in Sydney, Australia. “When that energy is insufficient, muscle contracts mechanically – or shivers – thereby generating heat. However, we did not know how muscle and fat communicate in this process.”
Volunteers in the study lay under a cooling water blanket, just wearing hospital scrubs. Most started shivering when the temperature fell to about 15C.
At the same time the researchers took blood samples to measure hormone levels, while devices attached to the skin measured electrical activity.
“We identified two hormones that are stimulated by cold – irisin and FGF21, released from shivering muscle and fat respectively,” Lee says. “These hormones fired up the energy-burning rate of human white fat cells in the laboratory and the treated fat cells began to emit heat, a hallmark of brown fat function.”
In the second part of the study, participants took part in exercise tests to compare the two processes. Exercising on a bicycle at a moderate level for an hour produced the same amount of irisin as shivering for 10 to 15 minutes.
The results suggest that exercise may mimic shivering in its hormonal effects, as both processes involve a similar type of muscle contraction.
“From a clinical point of view, irisin and FGF21 represent a cold-stimulated hormone system which was previously unknown and may be harnessed in future obesity therapeutics through brown fat activation,” Lee concludes.
Meanwhile, if you don’t fancy wintertime exercise, why not strip off, step into the cold and shiver for a few minutes?
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