Our Changing World for Thursday 19 May 2011
Dust in Antarctica
Alison Ballance caught up with Cliff Atkins and field assistant Jane Chewings at the end of their dust collecting adventures to find out what they'd been doing.(Image: A. Ballance)
We usually think of geologists as people who study rocks, but this summer a team of geologists from Victoria University of Wellington spent a couple of months in Antarctica collecting snow. They weren't so much interested in the snow, though, as what was in it - and that turned out to be surprisingly large amounts of dust.
Cliff Atkins has spent many years working on projects such as the Andrill drilling project, where they had noticed annual layers of dust in their sediment cores that were tied to evidence of annual phytoplankton blooms. It has long been known that its proximity to the Dry Valleys and the bare volcanic rock of Ross Island make McMurdo Sound one of the dustiest places in Antarctica, but Cliff decided it was time to quantify exactly where all the dust was coming from and how much was falling on the sea ice in McMurdo Sound each year. This would provide both information about the processes driving spring and summer phytoplankton blooms when the sea ice melts and the iron-rich dust 'falls' into the sea, and also help calibrate the geological sediment cores.
Genetically engineered clover
White clover (Trifolium repens) is an important part of New Zealand pastures. Like other legumes, white clover fixes nitrogen from the air, making it available (as nitrate) to other pasture grasses. The proportion of white clover in well-managed, fertile pastures can be up to 30 percent. But the downside is that white clover can cause bloat in some ruminant animals, and excess nitrate can contaminate waterways.
One way to avoid these unwanted effects is to increase the production of condensed tannins in the leaves of white clover. Condensed tannins are a complex group of chemical compounds that improve the protein uptake of grazing animals by binding to proteins in the plant matter and protecting them from being broken down by microbes in the rumen.
While there are some naturally occurring legumes that contain significant levels of tannins, white clover produces only trace amounts. Of the more than 250 different types of clover, only two are known to accumulate tannins in their leaves. Researchers at AgResearch in Palmerston North have used genetic techniques to identify a gene that is responsible for the high levels of tannins in Rabbitfoot clover (Trifolium arvense). A related gene in white clover remains switched off, but the team has developed transgenic cultivars that produce increased levels of tannins.
One hundred and fifty years ago, Austrian monk Gregor Mendel planted peas segregating for various characteristics, including flower colour.
But it wasn't until last year that a team of scientists, including Roger Hellens from Plant and Food Research, publishing in the journal PLoS-ONE, identified the genes that control for flower colour in pea plants. The paper describes two pea genes that regulate the production of anthocyanins, pigment molecules which accumulate to create colour in pea flowers. The work was a collaboration between scientists and Pland and Food Research, the John Innes Centre in the UK, URGV in France and the USDA's Agricultural Research Services. Ruth Beran speaks with Roger Hellens in a glasshouse in Palmerston North.
Simon Deroles and a gene gun, and two microscope images of a petal that has been shot with a reporter gene to determine whether the experiment has worked (middle), and a regulatory gene which makes the cells red (right) (Images: Tony Corbett, Plant and Food Research)
Using helium under vacuum to shoot gold nanoparticles with DNA into plants, biolistics was one of the tools used by Roger Hellens and his colleagues to test for the gene controlling flower colour in Mendel's peas (see story above).
To see the gun in action, Ruth Beran visits Simon Deroles in Palmerston North, and he shows her how Antirrhinum petals (Snap Dragon) are shot with a regulatory gene to turn on anthocyanin biosynthesis. A green fluorescent protein (GFP) reporter gene is also used to determine how successful the shooting procedure has been.