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Publications

When it comes to interdisciplinary collaboration, the titles of GLBRC publications speak for themselves. Each new year of operation has seen more publications from multiple labs that span the four Research Areas, accelerating the Center's production of the basic research that generates technology to convert cellulosic biomass to advanced biofuels.

Publications

BdCESA7 , BdCESA8 , and BdPMT  utility promoter constructs for targeted expression to secondary cell-wall-forming cells of grasses

Deborah L. Petrik; Cynthia L. Cass; Dharshana Padmakshan; Cliff E. Foster; John P. Vogel; Steven D. Karlen; John Ralph; John C. Sedbrook

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2016

Utility vectors with promoters that confer desired spatial and temporal expression patterns are useful tools for studying gene and cellular function and for industrial applications. To target the expression of DNA sequences of interest to cells forming plant secondary cell walls, which generate most of the vegetative biomass, upstream regulatory sequences of the Brachypodium distachyon lignin biosynthetic gene BdPMT and the cellulose synthase genes BdCESA7 and BdCESA8 were isolated and cloned into binary vectors designed for Agrobacterium-mediated transformation of monocots. Expression patterns were assessed using the beta-glucuronidase gene GUSPlus and X-glucuronide staining. All three promoters showed strong expression levels in stem tissue at the base of internodes where cell wall deposition is most active, in both vascular bundle xylem vessels and tracheids, and in interfascicular tissues, with expression less pronounced in developmentally older tissues. In leaves, BdCESA7 and BdCESA8 promoter-driven expression was strongest in leaf veins, leaf margins, and trichomes; relatively weaker and patchy expression was observed in the epidermis. BdPMT promoter-driven expression was similar to the BdCESA promoters expression patterns, including strong expression in trichomes. The intensity and extent of GUS staining varied considerably between transgenic lines, suggesting that positional effects influenced promoter activity. Introducing the BdPMT and BdCESA8 Open Reading Frames into BdPMT and BdCESA8 utility promoter binary vectors, respectively, and transforming those constructs into Brachypodium pmt and cesa8 loss-of-function mutants resulted in rescue of the corresponding mutant phenotypes. This work therefore validates the functionality of these utility promoter binary vectors for use in Brachypodium and likely other grass species. The identification, in Bdcesa8-1 T-DNA mutant stems, of an 80% reduction in crystalline cellulose levels confirms that the BdCESA8 gene is a secondary-cell-wall-forming cellulose synthase.

A novel pathway for triacylglycerol biosynthesis is responsible for the accumulation of massive quantities of glycerolipids in the surface wax of bayberry (Myrica pensylvanica ) fruit

Jeffrey P. Simpson; John B. Ohlrogge

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2016

Bayberry fruits synthesize an extremely thick and unusual layer of crystalline surface wax that accumulates to 30% of fruit dry weight, the highest reported surface lipid accumulation in plants. The composition is also striking, consisting of completely saturated triacylglycerol, diacylglycerol and monoacylglycerol with palmitate and myristate acyl chains. To gain insight into the unique properties of Bayberry wax synthesis we examined the chemical and morphological development of the wax layer, monitored wax biosynthesis through [14C]-radiolabeling, and sequenced the transcriptome. Radiolabeling identified sn-2 MAG as the first glycerolipid intermediate. The kinetics of [14C]-DAG and [14C]-TAG accumulation and the regiospecificity of their [14C]-acyl chains indicated distinct pools of acyl donors and that final TAG assembly occurs outside of cells. The most highly expressed genes were associated with production of cutin, whereas transcripts for conventional TAG synthesis were >50-fold less abundant. The biochemical and expression data together indicate that Bayberry surface glycerolipids are synthesized by a previously unknown pathway for TAG synthesis that is related to cutin biosynthesis. The combination of a unique surface wax and massive accumulation may aid understanding of how plants produce and secrete non-membrane glycerolipids, and also how to engineer alternative pathways for lipid production in non-seeds.

A superstructure-based framework for simultaneous process synthesis, heat integration, and utility plant design

Lingxun Kong; Murat Sen; Carlos A. Henao; James A. Dumesic; Christos T. Maravelias

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2016

We propose a superstructure optimization framework for process synthesis with simultaneous heat integration and utility plant design. Processing units in the chemical plant can be modeled using rigorous unit models or surrogate models generated from experimental results or off-line calculations. The utility plant subsystem includes multiple steam types with variable temperature and pressure. For the heat integration subsystem, we consider variable heat loads of process streams as well as variable intervals for the utilities. To enhance the solution of the resulting mixed-integer nonlinear programming models, we develop (1) new methods for the calculation of steam properties, (2) algorithms for variable bound calculation, and (3) systematic methods for the generation of redundant constraints. The applicability of our framework is illustrated through a biofuel case study which includes a novel non-enzymatic hydrolysis technology and new separation technologies, both of which are modeled based on experimental results.

Accuracy of genomic prediction in switchgrass (Panicum virgatum  L.) improved by accounting for linkage disequilibrium

Guillaume P. Ramstein; Joseph Evans; Shawn M. Kaeppler; Robert B. Mitchell; Kenneth P. Vogel; Robin Buell; Michael D. Casler

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2016

Switchgrass is a relatively high-yielding and environmentally sustainable biomass crop, but further genetic gains in biomass yield must be achieved to make it an economically viable bioenergy feedstock. Genomic selection is an attractive technology to generate rapid genetic gains in switchgrass and meet the goals of a substantial displacement of petroleum use with biofuels in the near future. In this study, we empirically assessed prediction procedures for genomic selection in two different populations consisting of 137 and 110 half-sib families of switchgrass, tested in two locations in the United States for three agronomic traits: dry matter yield, plant height and heading date. Marker data was produced for the families' parents by exome capture sequencing, generating up to 141,030 polymorphic markers with available genomic-location and annotation information. We evaluated prediction procedures that varied not only by learning schemes and prediction models, but also by the way the data was preprocessed to account for redundancy in marker information. More complex genomic prediction procedures were generally not significantly more accurate than the simplest procedure, likely due to limited population sizes. Nevertheless, a highly significant gain in prediction accuracy was achieved by transforming the marker data through a marker correlation matrix. Our results suggest that marker-data transformations and, more generally, the account of linkage disequilibrium among markers, offer valuable opportunities for improving prediction procedures in genomic selection. Some of the achieved prediction accuracies should motivate implementation of genomic selection in switchgrass breeding programs./p>.

Applications of constraint-based models for biochemical production

Cameron Cotten; Jennifer L. Reed

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2016

Biofuels are metabolic products, and knowledge of how metabolism operates is critical to understanding and improving biofuel production by microorganisms. Constraint-based metabolic modeling has been an important technique to broaden and deepen our knowledge of microbial metabolism and regulation. Genome-scale metabolic models enable global analysis of microbial metabolism by considering all metabolic reactions simultaneously. Genome-scale metabolic reconstructions are comprehensive listings of all the reactions, compounds, and genes that are involved in cellular metabolism for a particular organism. Constraint-based modeling methods use the information in metabolic reconstructions to predict intracellular fluxes and design strains for chemical and biofuel production. Recently, constraint-based modeling has been successful in designing a number of chemical production strains.

Biosynthesis of the plant cell wall matrix polysaccharide xyloglucan

Markus Pauly; Kenneth Keegstra

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2016

Xyloglucan (XyG) is a matrix polysaccharide that is present in the cell walls of all land plants. It consists of a beta-1,4-linked glucan backbone that is further substituted with xylosyl residues. These xylosyl residues can be further substituted with other glycosyl and nonglycosyl substituents that vary depending on the plant family and specific tissue. Advances in plant mutant isolation and characterization, functional genomics, and DNA sequencing have led to the identification of nearly all transferases and synthases necessary to synthesize XyG. Thus, in terms of the molecular mechanisms of plant cell wall polysaccharide biosynthesis, XyG is the most well understood. However, much remains to be learned about the molecular mechanisms of polysaccharide assembly and the regulation of these processes. Knowledge of the XyG biosynthetic machinery allows the XyG structure to be tailored in planta to ascertain the functions of this polysaccharide and its substituents in plant growth and interactions with the environment. Expected final online publication date for the Annual Review of Plant Biology Volume 67 is April 29, 2016. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.

Cellulosic feedstock production on Conservation Reserve Program land: potential yields and environmental effects

Stephen D. LeDuc; Xuesong Zhang; Christopher M. Clark; César Izaurralde

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2016

Producing biofuel feedstocks on current agricultural land raises questions of a “food-vs-fuel” tradeoff. The use of current or former Conservation Reserve Program (CRP) land offers an alternative; yet the volumes of ethanol that could be produced and the potential environmental impacts of such a policy are unclear. Here, we applied the Environmental Policy Integrated Climate (EPIC) model to a U.S. Department of Agriculture database of over 200,000 CRP polygons in Iowa, USA, as a case study. We simulated yields and environmental impacts of growing three cellulosic biofuel feedstocks on CRP land: (i) an Alamo-variety switchgrass (Panicum virgatum L.); (ii) a generalized mixture of C4 and C3 grasses; (iii) and no-till corn (Zea mays L.) with residue removal. We simulated yields, soil erosion, and soil carbon (C) and nitrogen (N) stocks and fluxes. We found that although no-till corn with residue removal produced approximately 2.6-4.4 times more ethanol per area compared to switchgrass and the grass mixture, it also led to 3.9-4.5 times more erosion, 4.4-5.2 times more cumulative N loss, and a 10% reduction in total soil carbon as opposed to a 6-11% increase. Switchgrass resulted in the best environmental outcomes even when expressed on a per liter ethanol basis. Our results suggest planting no-till corn with residue removal should only be done on low slope soils to minimize environmental concerns. Overall, this analysis provides additional information to policy makers on the potential outcome and effects of producing biofuel feedstocks on current or former conservation lands. This article is protected by copyright. All rights reserved.

Comparative productivity of alternative cellulosic bioenergy croppingsystems in the North Central USA

Gregg R. Sanford; Lawrence G. Oates; Poonam Jasrotia; Kurt D. Thelen; Philip Robertson; Randall D. Jackson

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2016

Biofuels from lignocellulosic feedstocks have the potential to improve a wide range of ecosystem services while simultaneously reducing dependence on fossil fuels. Here, we report on the six-year production potential (above ground net primary production, ANPP), post-frost harvested biomass (yield), and gross harvest efficiency (GHE = yield/ANPP) of seven model bioenergy cropping systems in both southcentral Wisconsin (ARL) and southwest Michigan (KBS). The cropping systems studied were continuous corn (Zea mays L.), switchgrass (Panicum virgatum L.), giant miscanthus (Miscanthus × giganteus Greef & Deuter ex Hodkinson & Renvoize), hybrid poplar (Populus nigra × P. maximowiczii A. Henry ‘NM6’), a native grass mixture (5 sown species), an early successional community, and a restored prairie (18 sown species). Overall the most productive cropping systems were corn > giant miscanthus > and switchgrass, which were significantly more productive than native grasses ≈ restored prairie ≈ early successional ≈ and hybrid poplar, although some systems (e.g. hybrid poplar) differed significantly by location. Highest total ANPP was observed in giant miscanthus (35.2 ± 2.0 Mg ha−1 yr−1) at KBS during the sixth growing season. Six-year cumulative biomass yield from hybrid poplar at KBS (55.4 ± 1.3 Mg ha−1) was high but significantly lower than corn and giant miscanthus (65.5 ± 1.5, 65.2 ± 5.5 Mg ha−1, respectively). Hypothesized yield advantages of diversity in perennial cropping systems were not observed during this period. Harvested biomass yields were 60, 56, and 44% of ANPP for corn, perennial grass, and restored prairie, respectively, suggesting that relatively simple changes in agronomic management (e.g. harvest timing and harvest equipment modification) may provide significant gains in bioenergy crop yields. Species composition was an important determinant of GHE in more diverse systems. Results show that well-established, dedicated bioenergy crops are capable of producing as much biomass as corn stover, but with fewer inputs.

Corn stover ethanol yield as affected by grain yield, Bt trait, and environment

Pavani Tumbalam; Kurt D. Thelen; Andrew Adkins; Bruce Dale; Venkatesh Balan; Christa Gunawan; Juan Gao

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2016

Literature values for glucose release from corn stover are highly variable which would likely result in tremendous variability in bio-refinery ethanol yield from corn stover feedstock. A relatively recent change in United States corn genetics is the inclusion of the Bacillus thuringiensis (Bt) trait, which now accounts for three-fourths of all US planted corn acreage. The objective of this study was to evaluate the effect of corn grain yield, inclusion of the Bt trait, and location environment on corn stover quality for subsequent ethanol conversion. Two hybrid pairs (each having a Bt and non-Bt near-isoline) were analyzed giving a total of 4 hybrids. In 2010 and 2011, field plots were located in Michigan at four lat- itudinal differing locations in four replicated plots at each location. Stover composition and enzymatic digestibility was analyzed and estimated ethanol yield (g g 1) was calculated based on hydrolyzable glucan and xylan levels. Analysis showed that there were no significant differences in total glucose or xylose levels nor in enzymatically hydrolyzable glucan and xylan concentrations between Bt corn stover and the non-Bt stover isolines. Regression analyses between corn grain yield (Mg ha 1) and corn stover ethanol yield (g g 1) showed an inverse relationship indicative of a photosynthate source-sink rela- tionship. Nevertheless, the quantity of stover produced was found to be more critical than the quality of stover produced in maximizing potential stover ethanol yield on a land area basis.

Designer lignins: Harnessing the plasticity of lignification

Yaseen Mottiar; Ruben Vanholme; Wout Boerjan; John Ralph; Shawn D. Mansfield

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2016

Lignin is a complex polyphenolic constituent of plant secondary cell walls. Inspired largely by the recalcitrance of lignin to biomass processing, plant engineering efforts have routinely sought to alter lignin quantity, composition, and structure by exploiting the inherent plasticity of lignin biosynthesis. More recently, researchers are attempting to strategically design plants for increased degradability by incorporating monomers that lead to a lower degree of polymerisation, reduced hydrophobicity, fewer bonds to other cell wall constituents, or novel chemically labile linkages in the polymer backbone. In addition, the incorporation of value-added structures could help valorise lignin. Designer lignins may satisfy the biological requirement for lignification in plants while improving the overall efficiency of biomass utilisation.

Detection of short-term cropping system-induced changes to soil bacterial communities differs among four molecular characterization methods

David S. Duncan; Kelsea A. Jewell; Garret Suen; Randall D. Jackson

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2016

Perennial grass-based agroecosystems are under consideration as sustainable sources of bioenergy feedstocks. Establishing these systems on land previously used for conventional agricultural production is expected to dramatically alter the composition and functional capacity of their associated soil bacterial communities, but the rate at which these changes will occur is unclear. Methods for characterizing bacterial communities are both varied and useful for documenting different aspects of the soil microbiota and their dynamics during this transition. Here, we studied the soil-associated bacterial communities of continuous corn and restored prairies systems within a cropping systems experiment 2–4 years after establishment using 1) phospholipid fatty acid (PLFA) profiling, 2) shotgun metagenomic sequencing, 3) amplicon sequencing of the 16S rRNA gene and 4) sequencing of the nitrogen-cycling gene nosZ. All characterization methods discriminated the bacterial communities between the two cropping systems, but the largest differences were observed with PLFA profiling. Differences between the two cropping systems did not significantly increase during the study period. The community compositions described by sequence-based methods were mutually correlated, but were only weakly correlated to the composition described by PLFA profiling. Shotgun metagenomics detected a much higher abundance of Actinobacteria than amplicon sequencing and revealed more consistent changes between cropping systems over time. Cropping system and interannual effects on the ratios of biomarkers associated with Gram-negative and Gram-positive bacteria were entirely different for PLFAs, rRNA amplicons, and shotgun-sequenced 16S rRNA. Our findings highlight how soil bacterial community characterization methods differ in their detection of microbial community composition as a result of recent land use change.

Different functions of phylogenetically distinct bacterial complex I isozymes

Melanie A. Spero; Joshua R. Brickner; Jordan T. Mollet; Tippapha Pisithkul; Daniel Amador-Noguez; Timothy J. Donohue

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2016

NADH:quinone oxidoreductase (complex I) is a bioenergetic enzyme that transfers electrons from NADH to quinone, conserving the energy of this reaction by contributing to the proton motive force. While the importance of NADH oxidation to mitochondrial aerobic respiration is well documented, the contribution of complex I to the different electron transport chains of bacteria has only been tested in a few species. The discovery that individual bacteria contain phylogenetically distinct complex I enzymes begs the question of whether individual isozymes serve different functions. Here, we analyze the function of two phylogenetically distinct complex I isozymes in Rhodobacter sphaeroides, an α-proteobacterium that contains well-characterized electron transport chains. We report that complex I function is central to R. sphaeroides energy metabolism, since a strain lacking both complex I isozymes grew more slowly via aerobic respiration and had anaerobic growth defects. Several observations also led us to conclude that the two complex I isozymes are not functionally redundant. For example, the complex I isozyme typically found in α-proteobacteria (referred to as complex IA) is required for photoheterotrophic growth on carbon sources whose catabolism is predicted to produce reduced quinone, while the isozyme that is commonly present in γ-proteobacteria (complex IE) is required for photoheterotrophic growth on carbon sources whose catabolism produces high levels of NADH. Additionally, complex IA is required to produce wild type levels of H2, while complex IE is dispensable for this process. We propose that these findings illustrate specific roles of complex I isozymes in either NADH synthesis (complex IA) or NADH oxidation (complex IE) during phototrophic growth. Unlike the singular role of complex I in mitochondrial aerobic respiration, we predict that the phylogenetically-distinct complex I isozymes found across bacterial species have evolved to enhance function in their respective electron transport chains

Does plant biomass manipulation in static chambers affect nitrous oxide emissions from soils?

Sarah M. Collier; Andrew P. Dean; Lawrence G. Oates; Matthew D. Ruark; Randall D. Jackson

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2016

One of the most widespread approaches for measurement of greenhouse gas emissions from soils involves the use of static chambers. This method is relatively inexpensive, is easily replicated, and is ideally suited to plot-based experimental systems. Among its limitations is the loss of detection sensitivity with increasing chamber height, which creates challenges for deployment in systems including tall vegetation. It is not always possible to avoid inclusion of plants within chambers or to extend chamber height to fully accommodate plant growth. Thus, in many systems, such as perennial forages and biomass crops, plants growing within static chambers must either be trimmed or folded during lid closure. Currently, data on how different types of biomass manipulation affect measured results is limited. Here, we compare the effects of cutting vs. folding of biomass on nitrous oxide measurements in switchgrass (Panicum virgatum L.) and alfalfa (Medicago sativa L.) systems. We report only limited evidence of treatment effects during discrete sampling events and little basis for concern that effects may intensify over time as biomass manipulation is repeatedly imposed. However, nonsignificant treatment effects that were consistently present amounted to significant overall trends in three out of the four systems studied. Such minor disparities in flux could amount to considerable quantities over time, suggesting that caution should be exercised when comparing cumulative emission values from studies using different biomass manipulation strategies.

Effective alkaline metal-catalyzed oxidative delignification of hybrid poplar

Aditya Bhalla; Namita Bansal; Ryan J. Stoklosa; Mackenzie Fountain; John Ralph; David B. Hodge; Eric L. Hegg

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2016

Strategies to improve copper-catalyzed alkaline hydrogen peroxide (Cu-AHP) pretreatment of hybrid poplar were investigated. These improvements included a combination of increasing hydrolysis yields, while simultaneously decreasing process inputs through (i) more efficient utilization of H2O2 and (ii) the addition of an alkaline extraction step prior to the metal-catalyzed AHP pretreatment. We hypothesized that utilizing this improved process could substantially lower the chemical inputs needed during pretreatment.

Electron partitioning in anoxic phototrophic bacteria

Melanie A. Spero; Saheed Imam; Daniel R. Noguera; Timothy J. Donohue

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2016

Photosynthetic cells make major contributions to many important processes on this planet, including solar energy capture, nitrogen or carbon dioxide sequestration and production of useful biocommodities. The sheer number of photosynthetic cells also makes them significant contributors to global nutrient cycling, especially in aquatic ecosystems. For each of these activities, photosynthetic cells need efficient systems for production and distribution of reducing power among the myriad of cellular pathways that depend on reductant. This chapter focuses on the partitioning of reductant in purple nonsulfur photosynthetic bacteria. It summarizes known membrane and cytoplasmic enzymes and pathways that need the reductant produced via photochemical activity (quinol in these organisms). These observations illustrate that quinol is used to provide reducing power to a variety of crucial cellular processes (cellular biosynthesis, maintenance of a proton motive force) and key assimilatory pathways (carbon dioxide and nitrogen fixation), depending on the availability of nutrients. We also summarize data illustrating that cells use a variety of pathways to recycle excess reductant. Finally, we illustrate how recent use of genomic and computational approaches to the analysis of these and other photosynthetic organisms has provided testable predictions and considerable new insight into the partitioning of reductant among that is produced from solar energy capture.

Evolution of VRN2/GhD7 -like genes in vernalization-mediated repression of grass flowering

Daniel P. Woods; Meghan A. McKeown; Yinxin Dong; Jill C. Preston; Richard M. Amasino

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2016

Flowering of many plant species is coordinated with seasonal environmental cues such as temperature and photoperiod. Vernalization provides competence to flower after prolonged cold exposure, and a vernalization requirement prevents flowering from occurring prior to winter. In winter wheat and barley, three genes VRN1, VRN2, and FT form a regulatory loop that regulates the initiation of flowering. Prior to cold exposure, VRN2 represses FT. During cold, VRN1 expression increases, resulting in the repression of VRN2, which in turn allows activation of FT during long days to induce flowering. Here we test whether the circuitry of this regulatory loop is conserved across Pooideae,consistent with their niche transition from the tropics to the temperate zone. Our phylogenetic analyses of VRN2-like genes reveal a duplication event occurred before the diversification of the grasses that gave rise to a CO9 and VRN2/GhD7 clade, and supports orthology between wheat/barley VRN2 and rice GhD7. Our Brachypodium distachyon VRN1 and VRN2 knockdown and overexpression experiments demonstrate functional conservation of grass VRN1 and VRN2 in the promotion and repression of flowering, respectively. However, expression analyses in a range of pooids demonstrate that the cold repression of VRN2 is unique to core Pooideae such as wheat and barley. Furthermore, VRN1 knock down in Brachypodium demonstrates that the VRN1 mediated suppression of VRN2 is not conserved. Thus, the VRN1-VRN2 feature of the regulatory loop appears to have evolved late in the diversification of temperate grasses.

Horizontally acquired genes in early-diverging pathogenic fungi enable the use of host nucleosides and nucleotides

Wiliam G. Alexander; Jennifer H. Wisecaver; Antonis Rokas; Chris T. Hittinger

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2016

How did nature engineer the highest surface lipid accumulation among plants? Exceptional expression of acyl-lipid-associated genes for the assembly of extracellular triacylglycerol by bayberry (Myrica pensylvanica ) fruits

Jeffrey P. Simpson; Nicholas Thrower; John B. Ohlrogge

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2016

Bayberry (Myrica pensylvanica) fruits are covered with a remarkably thick layer of crystalline wax consisting of triacylglycerol (TAG) and diacylglycerol (DAG) esterified exclusively with saturated fatty acids. As the only plant known to accumulate soluble glycerolipids as a major component of surface waxes, bayberry represents a novel system to investigate neutral lipid biosynthesis and lipid secretion by vegetative plant cells. The assembly of bayberry wax is distinct from conventional TAG and other surface waxes, and instead proceeds through a pathway related to cutin synthesis (Simpson and Ohlrogge, 2016). In this study, microscopic examination revealed that the fruit tissue that produces and secretes wax (bayberry knobs) is fully developed before wax accumulates and that wax is secreted to the surface without cell disruption. Comparison of transcript expression to genetically related tissues (bayberry leaves, M. rubra fruits), cutin-rich tomato and cherry fruit epidermis, and to oil-rich mesocarp and seeds, revealed exceptionally high expression of 13 transcripts for acyl-lipid metabolism together with down-regulation of fatty acid oxidases and desaturases. The predicted protein sequences of the most highly expressed lipid-related enzyme-encoding transcripts in bayberry knobs are 100% identical to the sequences from bayberry leaves, which do not produce surface DAG or TAG. Together, these results indicate that TAG biosynthesis and secretion in bayberry is achieved by both up and down-regulation of a small subset of genes related to the biosynthesis of cutin and saturated fatty acids, and also implies that modifications in gene expression, rather than evolution of new gene functions, was the major mechanism by which bayberry evolved its specialized lipid metabolism. This article is part of a Special Issue entitled: Plant Lipid Biology edited by Kent D. Chapman and Ivo Feussner.

How willing are landowners to supply land for bioenergy crops in the northern Great Lakes region?

Scott M. Swinton; Sophia Tanner; Bradford L. Barham; Daniel F. Mooney; Theodoros Skevas

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2016

Land to produce biomass is essential if the United States is to expand bioenergy supply. Use of agriculturally marginal land avoids the food vs fuel problems of food price rises and carbon debt that are associated with crop and forest land. Recent remote sensing studies have identified large areas of U.S. marginal land deemed suitable for bioenergy crops. Yet the sustainability benefits of growing bioenergy crops on marginal land only pertain if land is economically available. Scant attention has been paid to the willingness of landowners to supply land for bioenergy crops. Focusing on the northern tier of the Great Lakes, where grassland transitions to forest and land prices are low, this contingent valuation study reports on the willingness of a representative sample of 1107 private, non-corporate landowners to rent land for three bioenergy crops: corn, switchgrass, and poplar. Of the 11% of land that was agriculturally marginal, they were willing to make available no more than 21% for any bioenergy crop (switchgrass preferred on marginal land) at double the prevailing land rental rate in the region. At the same generous rental rate, of the 28% that is cropland they would rent up to 23% for bioenergy crops (corn preferred), while of the 55% that is forest land, they would rent up to 15% for bioenergy crops (poplar preferred). Regression results identified deterrents to land rental for bioenergy purposes included appreciation of environmental amenities and concern about rental disamenities. In sum, like landowners in the southern Great Lakes region, landowners in the Northern Tier are reluctant to supply marginal land for bioenergy crops. If rental markets existed, they would rent more crop and forest land for bioenergy crops than they would marginal land, which would generate carbon debt and opportunity costs in wood product and food markets. This article is protected by copyright. All rights reserved.

Identification of multiple lipid genes with modifications in expression and sequence associated with the evolution of hydroxy fatty acid accumulation in Physaria fendleri 

Patrick J. Horn; Jinjie Liu; Jean-Christophe Cocuron; Kate McGlew; Nicholas A. Thrower; Matt Larson; Chaofu Lu; Ana Paula Alonso; John Ohlrogge

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2016

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