Wood formation model to fuel progress in bioenergy

A new systems biology model mimicking the process of wood formation allows the prediction of effects in switching on and off genes involved in producing lignin. The model speeds the process of engineering trees for specific needs in timber, biofuel, pulp, paper and green chemistry applications.

“For the first time, we can predict the outcomes of modifying multiple genes involved in lignin biosynthesis, rather than working with a single gene at a time through trial and error, which is a tedious and time-consuming process,” said Dr Jack Wang, a member of the research team at North Carolina State University (NCSU).

Lignin gives strength and density to timber, but it must be removed from wood during biofuel, paper and pulp production through costly treatments that require high heat and harsh chemicals.

“Having a model such as this, which allows us to say if you want this type of wood, here are the genes that you need to modify, is very beneficial, especially when you have an enormous number of possible combinations with 21 pathway genes,” said Dr Wang. “It’s only possible through integrated analysis which allows us to look at this process at a systems level to see how genes, proteins and other components work together to regulate lignin production.”

The landmark lignin study may represent the most comprehensive model of a single pathway in a single plant species, according to Dr Wang. 

The model tracks 25 key wood traits. For timber, density and strength are paramount. Biofuel producers hone in on genes linked to high polysaccharide levels, allowing wood to be more easily converted to biodiesel or jet fuel. Pulp and paper producers look for wood with low lignin levels or wood that is more readily hydrolysed. High lignin woods are novel resources for the production of special value-added phenolic compounds.

New applications are already in the works, with a team of NCSU researchers exploring the production of trees that can be paired with thermophilic bacteria for optimal conversion to biofuels and biochemicals. Researchers are also looking at using the integrative analysis model to generate trees specifically tailored for production of nanocellulose fibres to replace petroleum-based materials such as plastic.

More than three dozen molecular geneticists, engineers, chemists and mathematicians have contributed to the model since 2008, including the painstaking process of producing thousands of transgenic trees, using the model tree species black cottonwood (Populus trichocarpa). Several researchers who initially contributed to the project as graduate students in the program now run labs of their own around the world.

The study highlights the utility of systems-level plant research, which researchers hope will inspire similar work on related pathways in other species.

They now have a base model where new higher level regulatory factors, such as transcription factors (regulatory proteins), regulatory RNAs and others important to growth and adaptation, can be incorporated to continuously improve the predictability and extend the application of the model. The next step will be the production of large varieties for field testing to acquire these important regulatory factors and to produce enough wood to identify their application specificity.

Image credit: Illustration by Jack Wang. Image by Hao-Chuan Huan

Source: Biomass Magazine