Environmental Molecular Sciences Laboratory

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Applying multi-dimensional solid state NMR to explore the nanoarchitecture of native and engineered plant cell walls

Date: 
Monday, October 1, 2018
Principal Investigator: 
Jennifer Mortimer
Lead Institution: 
Lawrence Berkeley National Laboratory
Project ID: 
50159
Abstract: 

Plants fix carbon via photosynthesis, the majority of which is incorporated into cell wall polysaccharides. These polysaccharides are synthesized in different cellular compartments, but are assembled outside the cell to form a complex biomaterial.
The cell wall is critical to human life. It provides us with materials, fuels, animal feed and dietary fiber. All plant cells have a thin primary cell wall that expands as the cell grows. Only some cells, when they stop growing, make a thick secondary cell wall. This secondary cell wall forms most of the plant biomass that we use, and is where most of the carbon is stored.

The secondary cell wall now has another proposed use - as a sustainable carbon source for the production of biofuels and biochemicals. Economically, this is currently challenging to do, and many scientific challenges remain. One strategy is to develop better biomass crops by improving the cell wall so that it is easier to deconstruct into simple sugars for microbial fermentation. Huge progress has been made to understand how the individual cell wall polymers are made. Now we need to understand how the different cell wall components are assembled together to make a functional biomaterial. This will allow us to predict how any changes might affect the cell wall as a whole. It will also allow us to develop improved deconstruction methods.

Unfortunately, all cell wall analysis methods require us to extract the plant cell wall and perform extensive processing. This means that all existing cell wall models require us to estimate what an intact cell wall will look like. The exception to this is multi-dimensional solid state nuclear magnetic resonance spectroscopy (ssNMR). We have recently shown, for the first time, that ssNMR is an ideal tool for looking at intact secondary cell wall. It requires us to grow plants in a 13CO2 atmosphere in a specially designed chamber to produce 13C labelled cell wall polymers. Previously we have looked at the model plant Arabidopsis. Now, I wish to extend this work to (1) analyze the cell wall of an Arabidopsis plant which has been engineered to have an increase in one specific cell wall polysaccharide (galactan) to look at the effect on cell wall architecture (2) analyze the cell wall of sorghum, a promising bioenergy crop that is the focus of much Department of Energy research. We will use both existing sorghum varieties, as well as new plants engineered as part of the DoE funded Joint Bioenergy Institute (JBEI).

The results from this project will be integrate with data produced in the JBEI program, including cell wall analysis using existing biochemical methods, as well as how these sorghum plants grow in the greenhouse and field. We expect to produce an improved understanding of cell wall architecture, and learn to predict how cell wall engineering will affect this.