Researchers Image Zinnia Cells Down to Nanoscale; Potential Aid for Lignocellulosic Biofuel Production
A team from Lawrence Livermore National Laboratory led by Michael Thelen, in collaboration with researchers from Lawrence Berkeley National Lab and the National Renewable Energy Laboratory, has examined the chemical and structural organization of the plant cell wall in Zinnia elegans tracheary elements (TEs). Tracheary elements are elongated cells in the xylem of vascular plants that serve in the transport of water and mineral salts.
Using three different microscopy methods (AFM, synchrotron radiation-based FTIR spectromicroscopy, and fluorescence microscopy using a cellulose-specific CBM) in conjunction with chemical extraction of wall components, the team was able to visualize single cells in detail down to the nanoscale, cellular substructures, fine-scale organization of the cell wall, and the chemical composition of these cells, indicating that they contain an abundance of lignocellulose.
In addition to providing insights in plant biology, such studies using Zinnia TEs could prove especially productive in assessing cell wall responses to enzymatic and microbial degradation, thus aiding current efforts in lignocellulosic biofuel production, the researchers suggested.
An open-access paper on their work was published 30 June in the journal Plant Physiology.
The leaves of Zinnia seedlings provide a rich source of single cells that are dark green with chloroplasts and can be cultured in liquid for several days at a time. During the culturing process, the cells change in shape to resemble the tube-like cells that carry water from roots to leaves. Known as xylem, these cells hold the bulk of cellulose and lignin in plants, which are both major targets of recent biofuel research.
The polymers, collectively called lignocellulose, are very insoluble, resistant to common chemicals and mechanical breakage, and are a superior substance for providing strength and structure to plants.
The detailed three-dimensional molecular cell wall structure of plants remains poorly understood.
To make fuels from plant biomass requires a thorough understanding of the organization of cell walls before determining the best methods for cell wall deconstruction into its components. Catherine Lacayo, a postdoctoral scientist working with Thelen and Malkin, has taken the first steps toward a comprehensive approach.
She came up with techniques that reveal the inner structure of cell walls in these single xylem cells, which represent about 70% of the cellulose in plants that can be used in fuel processing.
The research is supported by the Department of Energy Genome Sciences Program through the Office of Biological and Environmental Research, and the DOE’s BioEnergy Research Centers in Emeryville and Oak Ridge. It will appear in the September issue of Plant Physiology.
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