DNA barcoding is based on a gamble (or maybe a shrewd guess), and perhaps a smidgin of circular thinking: that there is a chunk of genome short enough to sequence quickly and cheaply, and which shows just enough variability for the entire sequence to be the same for all members of a species, but different for different species. Well, the gamble seems to have paid off. A suitable bit of a gene has duly been identified for both animals and plants, data are being ammassed, and there’s talk of a portable gadget being available in a few years which will read off the relevant sequence from a bit of leaf or skin or something and compare it with a database to give you the species name right there in the field.
Jack Hawkes: Obituary
It has been a bit of a wait, but worth it. London’s Daily telegraph carries a fine obituary of Jack Hawkes, who died a couple of weeks ago.
Hawkes recalled that Vavilov treated him “as an equal even though I was without a paper to my name. He inspired me with his extensive knowledge, friendship and boundless enthusiasm.” Tragically, Vavilov was to be executed on trumped-up charges in 1943 after falling foul of Trofim Lysenko, his successor as president of the Lenin Academy, a man whom Hawkes found to be “a dangerous, bigoted and wholly repellent person — a politician rather than a scientist, very able to ingratiate himself with Communist Moscow”.
And there you have, in a nutshell, much of the early history of plant genetic resources.
Hawkes met Vavilov just before setting out on the British Empire Potato Collecting Expedition to South America, covering 9000 miles and collecting more than 1100 acessions. The Indiana Jones meta-narrative lives on, of course, precisely because of men like Vavilov and Hawkes who made it their business to go out there and find the treasure. To their eternal credit, they shared the loot with all who asked.
Studying wild sunflowers
Rare wild sunflower gets the treatment.
Wheat disease genes
Fusarium graminearum is the fungus that causes Fusarium head blight, a serious disease of wheat and barley. FHB infects the flowers and makes itself at home in the seed, which ends up shrunken and white and loaded with toxins that can have a harmful effect on people and animals that eat the grain. A study just published in Science decoded the DNA sequence of the fungus and sheds some light on its virulence and variability ((The Fusarium graminearum Genome Reveals a Link Between Localized Polymorphism and Pathogen Specialization. Science: 317:1400 – 1402 DOI: 10.1126/science.1143708)).
The sequence of one strain is interesting enough, but the surprises emerged when the researchers, led by Corby Kistler at the University of Minnesota, compared two different strains. There were more than 10,000 differences between the two sequences. Those differences, however, were not spread evenly along the DNA; more than half of the differences were concentrated in just one eighth of the sequence.
So some regions of the genome are much less stable than others. And what genes are in those regions? Mostly ones concerned with infection and virulence, among them the genes for compounds that dissolve the host cell walls and others that digest host molecules so that the fungus can make use of them.
Just why the variability in Fusarium graminearum is concentrated in some areas of the DNA is not yet clear. These areas seem to be hotspots for recombination, which shuffles the DNA during sexual reproduction and so promotes diversity, but this particular fungus doesn’t go in for sexual reproduction all that often. A mystery, then, but one that may still yield new approaches to breeding resistant wheat and barley and perhaps to new kinds of treatment.
You may remember that a joint team of Israeli and US researchers recently reported that a wild relative of wheat, Sharon Goatgrass (Aegilops sharonensis), is loaded with resistance genes that protect it against seven of the most important fungal diseases of wheat. Alas, none of the samples tested was resistant to Fusarium head blight. How about some other wild relative species, though? We shall see.
Pigs didn’t fly, walked to Europe
We know that agriculture began in the Fertile Crescent about 12,000 years ago and then spread across Europe between 9,000 and 6,000 years ago. But what exactly was it that spread? Was it the idea of agriculture or agriculturalists themselves? Just-published work on the DNA of modern and ancient pigs says it was probably a bit of both. It seems that Middle Eastern farmers migrated into Europe carrying their agrobiodiversity with them — crops and domesticated animals. But, as far as the pig was concerned anyway, they soon adopted a locally domesticated version in preference to the Middle Eastern type they had brought along.