Article: High life prompts genetic shift


Robert Karl Sto

High life prompts genetic shift Extreme altitudes have created different coping strategies. 17
February 2004 HELEN PEARSON

Inhabitants of the harsh, high-altitude plateaus of the world have evolved to survive lofty
conditions in different ways, a new genetic study reveals.

Cynthia Beall of Case Western Reserve University in Cleveland, Ohio, studies the inhabitants of the
Tibetan plateau, the Ethiopian plateau and the Andean Altiplano in Peru and Bolivia - locations
where hardy residents routinely dwell at altitudes of more than 4,000 metres.

At these altitudes, the thin air leaves most tourists gasping for breath. "You're getting one third
less oxygen every time you take a lungful of air," says Beall. Yet the regular inhabitants appear
almost superhuman in their ability to function normally in such extreme conditions.

Previous studies have shown that the Tibetan, Ethiopian and Andean populations have developed
slightly different ways of boosting their oxygen levels to cope with the thin air. Those in the
Andes pump out more haemoglobin - a molecule that carries oxygen around in the blood. The Tibetans,
by contrast, have relatively low haemoglobin levels but breathe faster to take in more oxygen. "The
slightest bit of exercise makes them really pant," Beall says.

To understand what underlies these physiological changes, Beall has begun to explore each
population's genetic code: specifically, a short region of DNA in the cells' power-generating
mitochondria. This DNA is expected to contain distinctive sequences that might explain how cells
churn out energy with little oxygen to fuel them.

Beall has examined this DNA from several hundred people in populations from the Andes, Tibet and
Ethiopia. Their genetic sequences are largely dissimilar, she revealed at a meeting of the American
Association for the Advancement of Science in Seattle this week. This supports the idea that the
three groups have separately evolved different tactics to survive in the thin air.

Read the rest at Nature

Pigeons take the highway Some birds follow roads instead of flying direct. 10 February 2004 HELEN

Researchers may have discovered how pigeons find their way along familiar routes. Instead of
heading straight for their destination, they follow main roads, railways and rivers.

Tim Guilford and colleagues from Oxford University fitted more than 50 homing pigeons with tiny
tracking devices. They then monitored them, second by second, as they made the familiar journey back
to their loft.

Some of the birds that used landmarks did so again and again on separate occasions, says Guilford,
following a set path to theirloft. "One pigeon flies along the road to the first roundabout, takes
the third exit, goes along the dual carriageway to the next roundabout, then leaves the road and
goes cross-country," he says.

The birds can add an extra 20% or more to their journey by following these features, says Guilford.
It may be more demanding physically, he says, but easier mentally.

Other birds probably use a similar strategy. Even crows may not fly 'as the crow flies',
says Guilford.

Comment: Could pigeons be used as a navigation aid to blind motorists in much the same way as dogs
guide them on foot?

Talking to bacteria Researchers teach cells a new language. 12 February 2004 PHILIP BALL

Scientists have genetically engineered bacteria to 'talk' to each other in a new language1. The
achievement brings us one step closer to turning cells into tiny robots that we can control by
flooding them with chemicals.

Bacteria already communicate with each other by sending out chemical signals. A cell might release a
certain chemical in response to stress, for example, letting other cells nearby know they should
prepare for some unpleasant environmental conditions. When the chemicals reach a high enough
concentration, they switch on genes in neighbouring cells that change their behaviour.

But cells typically have a limited number of stimuli that provoke these chemical warnings, and a
limited number of chemicals that they can use to communicate. James Liao and co-workers at the
University of California, Los Angeles, wondered if they could get bacteria to talk using a
different chemical.

They started by stitching a 'module' of control genes into the genome of Escherichia coli bacteria -
these genes can switch on or off other genes naturally present in the bacteria. This technique has
been used before. For example, four years ago researchers at Princeton University in New Jersey
added a gene module to E. coli cells that made them blink on and off like light bulbs. The genes did
this by prompting the cells to make a light-emitting protein called GFP in regular spurts.2

Liao and colleagues went a step further, modifying E. coli cells to produce GFP only when triggered
by a chemical called acetate. Acetate is a normal by-product of the metabolism of E. coli - the
cells exude it constantly, rather like sweating. So the bacteria in Liao's lab constantly told each
other to light up.

The team managed to control the conversation by adjusting the acidity of the cell medium. In non-
acidic conditions, it takes more acetate to trigger a cell, so there needs to be a lot of cells
secreting acetate to start the conversation. In acidic conditions, just a few cells are enough to
start a chat.

Comment: Next we'll hear claims of 'bacteria consciousness'.

Boubous belt out victory duet Tropical crooners sing when they're winning. 14 February 2004 HELEN

Football fans aren't the only ones to celebrate a win with a rousing song. Tropical birds called
boubous do the same, a study has found.

The monogamous birds sing a special 'victory duet' after they have seen potential intruders off
their patch, report Ulmar Grafe of the University of Würzburg and Johannes Bitz of the German
Primate Centre in Göttingen, Germany, who studied the birds.

The researchers played recordings of four bird-song duets, which are often sung by boubous during
contests over territory, to 18 different bird couples in Africa's Comoé National Park on the
Ivory Coast.

Sixteen of the pairs stood their ground. Eleven of these 'winners' broke into their victory song
shortly after the recording was turned off. Losers never sang at all1.

"The duet is clearly a post-conflict display," says Grafe. Boubous are extremely territorial - they
probably sing to deter others from invading their patch, he says.

Posted by Robert Karl Stonjek.