Lignin is the double-edged sword of biofuels: if you are making cellulosic ethanol, you want less lignin because it blocks the breakdown of cellulose. If you are using pyrolytic methods, you want more lignin because lignin contains more energy than cellulose.
Whether you wish to maximize or minimize lignin content, an understanding of lignin synthesis is essential and has proved elusive. Lignin is a key adaptation to life on land, as it strengthens plant cell walls thereby helping land plants stand upright and reinforcing the cell walls of the specialized water-conducting tubes that are another key adaptation to growth in terrestrial environments.
The lignin polymer is made up of a complex arrangement of subunits and its subunit composition differs among different species. For example, ferns and conifers have lignin composed mainly of p-hydroxyphenyl (H) and guaiacyl (G) lignin units. Flowering plants have H and G subunits, plus syringyl (S) subunits derived from sinapyl alcohol. Interestingly, S lignin is also found in some lycophytes, including the spikemoss Selaginella (photo). In research published this week in The Plant Cell, a team of researchers led by Clint Chapple of Purdue University showed that lignin synthesis proceeds along a different path in Selaginella. Their work centers on the characterization of the enzyme ferulate 5-hydroxylase (F5H); in flowering plants, this enzyme produces S lignin units from G lignin precursors. By comparing the Selaginella enzyme (Sm F5H) to the F5H from the model flowering plant Arabidopsis thaliana (At F5H), the authors found that Sm F5H could both catalyze the same reaction as At F5H and could also catalyze an additional reaction, acting on precursors of H lignin to form precursors to G and S lignin, and thereby bypassing four steps in angiosperm lignin synthesis. Indeed, transgenic expression of Sm F5H can restore normal lignin deposition to Arabidopsis plants with mutations in other enzymes of lignin biosynthesis. Interestingly, some combinations of transgenic Sm F5H and Arabidopsis lignin mutations produce lignin compositions likely not seen in nature, indicating that manipulation of this pathway can be used to engineer lignin composition. Moreover, since different lignin subunit compositions produce different lignin structural properties, this engineering may affect biomass characteristics such as digestibility. Author Clinton Chapple notes “It is exciting to realize that the study of plants so distantly related to crops can provide us with new tools to engineer plants that are of benefit to humans.”
This research also provides interesting insights on convergent evolution, the process whereby different evolutionary lineages arrive at similar adaptations, such as the independent evolution of wings for flight in bats and birds. Selaginella is part of one of the oldest divisions of vascular plants, resulting from an ancient split between the lycophytes and euphyllophytes (which include all modern seed plants). Similar to bat wings and bird wings, the synthesis of S lignin appears to have arisen independently in flowering plants and in lycophytes. Thus, this research provides both an interesting window on convergent evolution in plants and a potentially useful tool for engineering lignin synthesis.
This research was supported by the National Science Foundation, the U.S. Department of Energy office of Science, and the Life Sciences Research Foundation.
Jennifer Mach | EurekAlert!
New insights into the information processing of motor neurons
22.02.2017 | Max Planck Florida Institute for Neuroscience
Wintering ducks connect isolated wetlands by dispersing plant seeds
22.02.2017 | Utrecht University
In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport
Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...
The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.
The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...
Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...
Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".
Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...
13.02.2017 | Event News
10.02.2017 | Event News
09.02.2017 | Event News
22.02.2017 | Power and Electrical Engineering
22.02.2017 | Life Sciences
22.02.2017 | Innovative Products