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Genome tweaks may lead to better trees for paper

N.C. State research: Micro RNA controls what gives strength to wood

CorrespondentJuly 7, 2013 

Dr. Vincent Chiang co-directs NC State's Forest Biotechnology Research Center.


In the complex process of gene expression, DNA is copied into RNA, which tells a cell to make chemical structures essential for life. Numerous molecules regulate this chain of events and can affect which chemical structures are made. As it turns out, one class of tiny and mysterious molecules, called “micro RNAs,” may play a pivotal role.

Though micro RNAs were not widely recognized until the early 2000s, they have been studied intensely since then, as scientists seek to understand their role in genetic expression. One group, led by Vincent Chiang of N.C. State’s Forest Biotechnology Research Center, recently found that micro RNAs in plant cells control how much lignin the plants make.

Lignin is the chemical compound that gives wood its strength and makes newsprint stronger than printer paper. The process that creates lignin occurs in all plant cells. When a plant needs more lignin – such as in its trunk – micro RNA allows the plant to make more of it. When a plant needs less lignin, such as in its leaves, micro RNA prevents the plant from making it.

“I always thought there would be some master regulator,” Chiang said. “The important discovery (of this recent work) is that this is the first time we’ve found a micro RNA that controls lignin biosynthesis.”

In a 2005 paper published in the journal Plant Cell, Chiang and colleagues reported discovering lots of different micro RNAs that control a plant’s ability to make wood. The team then began to test these micro RNAs, and recently determined which one controls how much lignin is made.

The team reported their results in the June edition of the Journal Proceedings of the National Academy of Sciences.

“In the genome of some trees, there are probably 150 to 200 micro RNAs that control thousands of genes,” Chiang said.

“We discovered lots of wood-specific micro RNAs, and I thought there would be one that controlled lignin.”

Since lignin gives wood its strength, it must be removed from the wood before print paper can be made. The same can be said for the production of “biomass energy.”

In that process, lignin must be removed from wood, before the remaining material can be converted into ethanol for fuel.

Normally, chemicals remove lignin – but those chemicals can cause pollution and other problems.

The researchers’ findings may make it possible to breed trees with extra micro RNA, which would lower trees’ lignin content. This could ultimately reduce the need for chemicals to transform the wood into commercial products.

“If you start with wood that has less lignin, you need fewer chemicals to treat it,” Chiang said.

“The same thing goes with biomass. Lignin is a barrier. You need to remove lignin to more easily process the wood into ethanol.”

According to Chiang, the synthesis of lignin in a plant cell involves many different genes, and thus may be regulated by multiple micro RNAs or other similar molecules. His lab intends to further investigate which ones are involved, in order to better understand the entire process.

“Micro RNA is a very powerful control,” Chiang said. “This is lifelong research.”

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