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Geneticists Reveal How Trees Know To Grow

Stu Hutson

Countless words have been put to paper over the years in attempts to describe the beauty of a tree — including carefully crafted passages by the world’s most gifted writers. But those writings pale in comparison to the intricacy of a tree’s own genetic script.

A team led by UF geneticist Matias Kirst has completed a first study of how the byzantine interplay of elements within a tree’s genetic code spell out different structures, such as leaves, trunk and roots.

All cells in a tree have the same genetic information, whether it’s in a leaf or a root. However, how that genetic information is translated into the various tree structures is based on a complex set of interactions, said Kirst, a researcher with the UF Genetics Institute.

In the English language, a silent “e” on the end of a word can affect how the vowels in the middle of the word are pronounced. Even a word’s placement in a sentence can change its meaning.

Similarly, the expression of genes spelled out in one section of DNA is often regulated by a gene or multiple genes somewhere else in the genetic code. In turn, those genes moderate the activities of others — forming networks of intertwined genetic activity.

In a paper published in May in the Proceedings of the National Academy of Sciences, the team reports the first mapping of these networks of interactions as they affect different parts of two types of cottonwood trees.

While similar genetic network mapping has been done of human cells, this represents the first time that this level of understanding has been reached in the plant world.

The analysis also revealed that certain gene networks are active only within specific parts of the tree. Meanwhile, other gene networks were active throughout the tree.

Knowing which genes are expressed only in some parts of the tree and which are expressed throughout the tree is key to researchers and breeders attempting to develop trees and other plants best suited for biofuel, pulp, paper and timber production, Kirst said.

The work will help develop trees that are specifically suited to being used as feedstock for cellulosic ethanol, an environmentally friendly and renewable substitute for gasoline.

However, it is likely that many other plants will have similar gene networks to those discovered in the cottonwood trees — potentially leading to more sophisticated ways of improving food crops.

Kirst also was recently awarded $873,000 over five years to conduct a radically new genetic analysis of poplar trees — an effort that may help harness the trees as a sustainable and economical fuel source.

Kirst was the only researcher from Florida to receive U.S. Department of Energy special funding under the American Recovery and Reinvestment Act of 2009.

This funding will support Kirst’s innovative method for comparing different poplar trees to find out which genes contribute to properties important to bioenergy production.

Matias Kirst,