Annalee Newitz in io9:
The poplar tree's genome has been sequenced and it has 42 thousand genes — roughly twice the number as a human. It turns out that this is typical for a perennial plant like the poplar. Though we animals think of ourselves as far more sophisticated than plants, Tuskan explained that trees have to be a lot tougher and more resilient than the typical animal. He explained:
Humans or mice or elephants can move. If it's cold they can go underground or build shelter. Perennial plants have to stand there and take it for thousands of years in some cases — they have to be equipped biochemically for a drought, ready for heat or cold, ready for an insect attack. I think that's part of why plants have larger arrays of genes — that's their way of surviving.
Out of all these genes, only a handful may turn out to be useful for industry. “Half of the genes have no known function,” Tuskan said, “and with lignin it's probably somewhere between a dozen and three or four dozen genes that will turn out to be important.”
A lot of what Tuskan's lab does with poplars is an effort to link the behavior of specific genes to physical traits in the tree. This kind of analysis is called a genome-wide association study or GWAS, which everybody in the field pronounces “gee wass,” like J-Lo for genome geeks. “Basically it's figuring out the genome's relationship to the phenotype,” said Tuskan.
He and his colleagues have already had some success isolating genes that control various aspects of the tree's metabolism. In one case, they were able to start and stop the growth of a symbiotic fungus in poplar tree roots. Ultimately, Tuskan would like to have genetic switches that control many aspects of the poplar's development. Farmers could do things like grow a tree that's designed to have more lignin or less, depending on what the market demands.
More here.