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!
Researchers uncover protein-based “cancer signature”
05.12.2016 | Universität Basel
The Nagoya Protocol Creates Disadvantages for Many Countries when Applied to Microorganisms
05.12.2016 | Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
05.12.2016 | Power and Electrical Engineering
05.12.2016 | Information Technology
05.12.2016 | Earth Sciences