Transcription Factor Amr1 Induces Melanin Biosynthesis and Suppresses Virulence in Alternaria brassicicola
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Physicochemical Changes of Cellulose and Their Influences on Populus trichocarpa Digestibility after Different Pretreatments
Pretreatment is commonly used to reduce recalcitrance of the lignin-carbohydrate matrix. In this study, leading pretreatment technologies, including dilute sulfuric acid, liquid hot water, alkaline, and organosolv pretreatments, were applied to the selected Populus trichocarpa genotype with relatively low lignin content to elucidate cellulose physicochemical property changes and digestibility-related factors. Pretreated Populus trichocarpa (BESC 131) exhibited higher accessibility and glucose yield than the untreated biomass. Chemical composition and Fourier transform infrared (FTIR) analysis results revealed that hemicellulose and lignin were removed to a varying extent depending on the pretreatment techniques applied. Here, the degree of polymerization of the cellulose was decreased to the largest extent after dilute acid pretreatment, followed by organosolv, alkaline, and liquid hot water pretreatments. Cellulose crystallinity index was slightly changed after the pretreatments; however, its differences were not remarkable between those pretreatment techniques. Among four different pretreatments, organosolv was the most effective pretreatment technology in terms of sugar release, which was three times higher than that of the untreated native biomass. Among all of the tested cell wall traits, the lignin content of Populus trichocarpa was the most remarkable feature associated with glucose release, though Populus trichocarpa recalcitrance was not solely dependent on any single factor.
59 BASIC BIOLOGICAL SCIENCES↗
Effects of Porous Medium Heterogeneity on Vadose Zone Desiccation: Intermediate-scale Laboratory Experiments and Simulations
Soil desiccation (drying), involving water evaporation induced by dry gas injection, is a potentially robust vadose zone remediation process to limit contaminant transport through the vadose zone. A series of four intermediate-scale flow cell experiments was conducted in homogeneous and simple layered heterogeneous porous medium systems to investigate the effects of heterogeneity on desiccation of unsaturated porous media. The permeability ratios of porous medium layers ranged from about five to almost two orders of magnitude. The insulated flow cell was equipped with twenty humidity and temperature sensors and a dual-energy gamma system was used to determine water saturations at various times. The multiphase code STOMP was used to simulate the desiccation process. Results show that injected dry gas flowed predominantly in the higher permeability layer and delayed water removal from the lower permeability material. For the configurations tested, water vapor diffusion from the lower to the higher permeability zone was considerable over the duration of the experiments, resulting in much larger relative humidity values of the outgoing air than based on permeability ratios alone. Acceptable numerical matches with the experimental data were obtained when an extension of the saturation-capillary pressure relation below the residual water saturation was used. The agreements between numerical and experimental results suggest that the correct physics are implemented in the simulator and that the thermal and hydraulic properties of the porous media, flow cell wall and insulation materials were properly represented.
contaminant transport↗
Manipulation Of Lignin Biosynthesis To Maximize Ethanol Production From Populus Feedstocks
Our research focuses on transgenic strategies for modifying lignification to improve biomass quality, without leading to deleterious effects on plant performance. In order to accomplish this objective, we designed molecular strategies and selected appropriate transgenes for manipulating the expression of lignification-associated genes; we generated poplar engineered for altered lignin content and/or monomer composition, and field-tested them for fitness; we analyzed the impact of these transgenic strategies on metabolism in general and lignin biosynthesis in particular; and evaluated the ease with which cell wall deconstruction can be accomplished using both chemical and enzymatic means using wild-type and high syringyl poplar.
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Probing Product Binding in Cellulase Enzymes [Fact Sheet]
Large-scale computer simulations offer a new interpretation for the discrepancy in experimentally measured product inhibition constants in cellulase enzymes. The simulations also suggest new strategies for relieving product inhibition, which is key for the application of enzymes in the biofuels industry. Bacteria and fungi secrete enzyme cocktails consisting of processive and nonprocessive enzymes, which act synergistically to digest plant cell walls. As high-solids loadings are important for economically viable biomass conversion processes, the concentrations of glucose and cellobiose reached during enzymatic hydrolysis often cause a significant slow-down in cellulase activity through enzyme inhibition. Many studies have quantified cellulase product inhibition, but experimental measurements of product binding constants vary dramatically, and there is little consensus on the importance of this phenomenon. To provide molecular insights into cellulase product binding, scientists from the National Renewable Energy Laboratory (NREL) used computer simulation to demonstrate that the presence of cellodextrins bound in the substrate sites of cellulases, which are present during enzymatic catalysis, can increase cellobiose binding to processive cellulases by several orders of magnitude, whereas this presence has no effect on product binding in nonprocessive cellulases. These findings provide new insights into the large discrepancies reported for binding constants for cellulases. This work also suggests that catalytic engagement has an important effect on apparent inhibition constants for processive cellulases and should be taken into account to characterize product inhibition. Additionally, several computationally designed mutants of the processive cellulases are demonstrated to be able to reduce the cellobiose binding affinity, which suggests a means to engineer cellulases to improve the efficiency of biomass conversion.
09 BIOMASS FUELS↗
Exploring the Genome and Proteome of Desulfitobacterium hafniense DCB2 for its Protein Complexes Involved in Metal Reduction and Dechlorination
Desulfitobacteria are of interest to DOE mission because of their ability to reduce many electron acceptors including Fe(III), U(VI), Cr(VI), As(V), Mn(IV), Se(VI), NO 3 - and well as CO 2 , sulfite, fumarate and humates, their ability to colonize more stressful environments because they form spores, fix nitrogen and they have the more protective Gram positive cell walls. Furthermore at least some of them reductively dechlorinate aromatic and aliphatic pollutants. Importantly, most of the metals and the organochlorine reductions are coupled to ATP production and support growth providing for the organism's natural selection at DOE's contaminant sites. This work was undertaken to gain insight into the genetic and metabolic pathways involved in dissimilatory metal reduction and reductive dechlorination, (ii) to discern the commonalities among these electron-accepting processes, (iii) to identify multi-protein complexes catalyzing these functions and (iv) to elucidate the coordination in expression of these pathways and processes.
59 BASIC BIOLOGICAL SCIENCES↗
Lignin as a facilitator, not a barrier, during saccharification by brown rot fungi
This research focused on the biology of a group of wood-degrading fungi that cause brown rot in wood, with particular attention to the potential to mimic this biological approach ex situ for bioprocessing lignocellulosic biomass. Supported by the long-standing theory that these fungi use a two-step oxidative/enzymatic approach during brown rot, our team’s objectives were as follows: 1) to determine the discrete timing of lignin modifications, 2) to correlate these alterations with biocatalyst efficiency and ingress into plant cell walls, and 3) to reproduce modifications prior to saccharification for efficient bioprocessing. The core findings of our research were that 1) lignin modifications occur nearly coincident with enzyme secretion during brown rot and 2) there is no specificity to the benefit that a brown rot pretreatment has on the efficacy of cellulases – it is a general enhancement best predicted by chemical changes to lignin and side-chain hemicellulose sugars. In our work, this meant we could attain and predict broad improvements in saccharification using commercial cellulase cocktails, in some cases more than three-fold of that in untreated biomass. This project was completed with minimal variance from the original project management plan (PMP), resulting in fourteen presentations and posters, four peer-reviewed publications, and one additional publication now in review. The publications have been valuable to other scientists working toward similar goals and have been cited in thirteen peer-reviewed publications written by others since 2010. We are working with ADM to advance application options for industry, building on the lessons learned during this DOE award period.
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NREL Breaks New Ground in Plant Pretreatment for Biofuels (Fact Sheet)
NREL researchers use imaging technologies to broaden knowledge of plant cell wall structures and identify ideal pretreatment of plant material.
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Assessing the Importance and Impact of Glycomics and Glycosciences Phase II
Glycans form one of the four basic classes of macromolecules in living systems, along with nucleic acids, proteins, and lipids. They are composed of individual sugar units that can be linked to one another in multiple ways, enabling them to form complex three-dimensional structures. In living systems, glycans are involved in myriad processes that are part of normal cellular physiology, development, and signaling, as well as in the development of both chronic and infectious diseases. Because of their ubiquity on cell surfaces, they are key components of biological interfaces and are involved in molecular recognition and signaling. They are also important molecules in cell adhesion and cell movement. Meanwhile, glycans on proteins inside cells participate in the cell’s responses to incoming signals, for example by helping to modulate gene expression and protein functions. Glycan polymers such as cellulose are important components of plant cell walls. Understanding how such walls are assembled and how they can be deconstructed is fundamental to basic plant biology, but also in the development of applications such as efficient conversion of biomass into fuels. Glycan polymers derived from plants and other organisms can also serve as sources of new materials with wide-ranging applications from tissue engineering scaffolds to flexible electronic displays. Achieving an understanding of the structures and functions of glycans is fundamental to understanding biology. The National Research Council report resulting from this project, Transforming Glycoscience: A Roadmap for the Future, discusses the impact glycoscience can have across health, energy, and materials science and lays out a roadmap of research goals whose achievement could help the field become a widely-recognized and integrated discipline rather than a niche area studied by a small number of specialists. Despite advances, gaps remain in the current suite of tools for investigating glycans and these tools often require expert users and facilities, presenting a barrier for many investigators. The field is poised to benefit from the pursuit of the framework laid out in the study, which incorporates not only human physiology and health but also plant, animal, and microbial research and efforts to improve tools for synthesis, analysis, data management, and other fundamental research infrastructure.
59 BASIC BIOLOGICAL SCIENCES↗
Genetic dissection of bioenerrgy traits in sorghum
Specific Objectives: 1. To identify the gene(s) underlying a major QTL for stem sugar concentration located on chromosome 3. 2. To identify QTL for stem juice volume and stalk sugar concentration and to identify the underlying genes. 3. To classify 60 novel sorghum bmr mutants from the USDA TILLING population in allelic groups based on cell wall chemistry and allelism tests. 4. To select representative bmr mutants from each allelic group and selected NIR spectral mutants for their potential value as feedstock for ethanol production. 5. To clone and characterize those Bmr genes that represent loci other than Bmr12 and Bmr6 using a mapping and a candidate gene approach.
59 BASIC BIOLOGICAL SCIENCES↗
Final Scientific/Technical report for "ABI8: Prototype of a novel signaling factor"
The Arabidopsis thaliana ABSCISIC ACID-INSENSITIVE8 locus encodes a highly conserved plant-specific protein that mediates abscisic acid (ABA) and sugar responses essential for growth. Although initial database comparisons revealed no domains of predictable function, it has recently been re-annotated as a member of the Glycosyltransferase family A. However, this function has not been demonstrated experimentally and no specific substrates have been identified. Mutations affecting ABI8 are near-lethal due to pleiotropic yet specific effects including altered ABA signaling, sugar transport, cell wall synthesis, root meristem maintenance, vascular patterning, and male sterility. Because the predicted sequence initially provided no clues, we used a guilt by association strategy to address function of this protein by determining its subcellular localization and identifying interacting proteins. Our studies showed that ABI8 is localized to the endomembrane system and may interact with proteins implicated in Golgi trafficking, lignification, and stress signaling. We found that the root meristem arrest reflects decreased auxin accumulation and resulting decreases in regulators required for meristem identity, all of which can be rescued by added glucose. Further studies showed that this glucose-dependence reflects reduced glucose uptake as well as the decreased expression of sugar-mobilizing enzymes. This work suggests that ABI8 may regulate trafficking of membrane proteins such as auxin transporters and cellulose synthase, but this hypothesis has not yet been tested. The altered gene expression is likely to be a secondary or later effect of this pleiotropic mutation.
59 BASIC BIOLOGICAL SCIENCES↗
Analysis of Microbial Activity Under a Supercritical CO 2 Atmosphere
Because the extent and impact of microbial activity in deep saline aquifers during geologic sequestration is unknown, the objectives of this proposal were to: (1) characterize the growth requirements and optima of a biofilm-producing supercritical CO 2 -tolerant microbial consortium (labeled MIT0212) isolated from hydrocarbons recovered from the Frio Ridge, TX carbon sequestration site; (2) evaluate the ability of this consortium to grow under simulated reservoir conditions associated with supercritical CO 2 injection; (3) isolate and characterize individual microbial strains from this consortium; and (4) investigate the mechanisms of supercritical CO 2 tolerance in isolated strains and the consortium through genome-enabled studies. Molecular analysis of genetic diversity in the consortium MIT0212 revealed a predominance of sequences closely related to species of the spore-forming genus Bacillus. Strain MIT0214 was isolated from this consortium and characterized by physiological profiling and genomic analysis. We have shown that the strain MIT0214 is an aerobic spore-former and capable of facultative anaerobic growth under both reducing N 2 and CO 2 atmospheres by fermentation and possibly anaerobic respiration. Strain MIT0214 is best adapted to anaerobic growth at pressures of 1 atm but is able to growth at elevated pressures After 1 week growth was observed at pressures as high as 27 atm (N 2 ) or 9 atm (CO 2 ) and after 26-30 days growth can be observed under supercritical CO 2 . In addition, we have determined that spores of strain B. cereus MIT0214 are tolerant of both direct and indirect exposure to supercritical CO 2 . Additional physiological characterization under aerobic conditions have revealed MIT0214 is able to grow from temperature of 21 to 45 °C and salinities 0.01 to 40 g/L NaCl with optimal growth occurring at 30°C and from 1 - 5 g NaCl/L. The genome sequence of B. cereus MIT0214 shared 89 to 91% of genes with other genome-sequenced strains with 93.3 to 97.8% nucleotide identity among shared genes. Comparison of the sequence of MIT0214 or a B. cereus strain isolated from an oil well in China to B. cereus isolates from surface environments revealed a higher proportion of genes involved in Cell wall and capsule biosynthesis and metabolism, metabolism of aromatic compounds, and stress response. Since Bacillus species, including B. cereus strains, have commonly been recovered from other “extreme” environments including the deep subsurface – the scCO 2 tolerance of spores and growth under high pCO 2 conditions is consistent with persistence in a subsurface environment after CO 2 injection.
54 ENVIRONMENTAL SCIENCES↗
FINAL REPORT
Excellent progress was made in standardizing three complementary methods: Magnetic resonance imaging, x-ray micro CT, and MALDI imaging linear ion trap mass spectroscopy to image biomass and chemical, anatomical and functional changes that occur during pretreatment and hydrolysis. Magnetic resonance microscopy provides excellent images with as low as 5 uM resolution with hydrated biomass samples. We visualized dramatic changes in signal associated with the hydrolysis of the carbohydrates by strong acids. Quantitative diffusion approaches were used to probe more subtle structural changes in biomass. Diffusion tensor calculations reflect diffusion anisotropy and fractional anisotropy maps clearly show the longer range diffusion within the vessels compared to within the fiber cells. The diffusion is increased along the cell walls of the vessels. Suggesting that further research with NMR imaging should be pursued. X-ray CT provides excellent images at as low as 3.5 uM resolution from dried biomass. Small increases in surface area, and decreases in local density have been quantified in with wood after mild pretreatments; these changes are expected to be underestimates of the hydrated wood, due to the ~12% shrinkage that occurs upon drying untreated wood. MALDI-MS spectra show high ion intensities at most mass to charge ratios in untreated and pretreated woody material. MALDI-MSn is required to improve specificity and reduce background for imaging. MALDI-TOF is not specific enough for carbohydrate identification. Using MALDI-LIT/MSn we can readily identify oligomeric glucans and xylans and their fragmentation patterns as well as those of the glucuronic acid side chains of birch 4-O-methyl glucuronxylan. Imaging of glucan and xylan oligomers show that many contain isobaric ions with different distributions, indicating again that MSn is needed for accurate imaging of lignocellulosic materials. We are now starting to integrate the three imaging methods by using the same set of biomass samples imaged with all three methods, and using common analytical software to quantify parameters from the three dimensional images. In addition to the proposed experiments, we conducted imaging studies with a novel TOF-SIMS instrument available through collaborations with the AMOLF goup led by Ron Heeren at the FOM Institute in Amersterdam, Netherlands. ToF-SIMS was used to image intact cross sections of Populus stems with high spatial resolution, chemically selectivity. ToF-SIMS images were correlated with fluorescence microscopy which allowed for more positive ion identification.
09 BIOMASS FUELS↗
The Hunt for Green Every April: Factors Affecting Fitness in Switchgrass
This grant funded work was undertaken to develop fundamental biological knowledge of the factors affecting the complex plant trait “fitness” in switchgrass (Panicum virgatum L.), a plant being developed as a biomass crop. Using a diverse range of latitudinally-adapted switchgrass plants, genomic, molecular and physiological studies were performed to track a number of different aspects of plant genetics and physiology over the course of the growing season. Work was performed on both genetically unrelated and genetically related plants. Plants were established in the field from seedlings raised in a greenhouse, or from clones present in other field nurseries. Field grown plants were used as the source of all tissues. The three objectives of this proposal were:(1) Transcript Profiling, Metabolomics, and C and N Partitioning and Recycling in Crowns and Rhizomes of Switchgrass over two growing seasons; (2) Gene Profiling During Regreening and Dormancy of Bulked Segregants; (3) Extent of Linkage Disequilibrium in Populations for Adaptation and Fitness Traits Being Developed for Central and Northern USA, that Show Significant Heterosis. Objective 1 results: Plants were labeled using 13 CO2 (a stable isotope) using an acrylic chamber constructed specifically for this purpose. Plants became labeled with 13 C and label decayed in aerial tissues over the course of the growing season. Varying amounts of 13 C were recovered in the rhizomes. These data are being analyzed. Plants were also labeled with 15 N-urea. Plants absorbed significant amounts of label that was remobilized to the growing shoots. N-dynamics would suggest that a portion of the 15 N absorbed into the crowns and rhizomes is sequestered below ground. Variable amounts of 15 N were translocated from the shoots to the roots over the course of the growing season. Polar metabolites extracted from a diverse array of rhizomes were analyzed using GCMS. Data indicated that there was a significant shift in metabolite pools over the course of the growing season, and differences in the levels of specific metabolites could be linked to the progression of dormancy. Several metabolites that accumulate in dormant rhizomes were identified. Some of these metabolites could be potentially linked to winter-survival of switchgrass. Extensive high-throughput sequencing was conducted on crown and rhizome samples collected from field grown plants. Initial work was performed on a Roche 454 system. All later work was performed on an Illumina sequencing-by-synthesis system. Some of these datasets have been published as peer-reviewed papers, other data are currently being analyzed and being readied for publication. Objective 2 results: Genetically related but phenotypically divergent plants from an octaploid switchgrass population were grown in a replicated field nursery. Rhizomes were harvested at four different times over the course of the growing season from plants with high winter survival and those with lower winter survival. RNA-Seq was performed on harvested materials. Initial analysis suggests that plants with lowered winter survival experience a greater level of cellular stress in dormant tissues. This aspect of plant function is being probed in greater depth. Objective 3 results: A total of 592 individual clones with three clonal replications in a randomized complete block design from each of five populations used in Objective 1 studies were rated for heading date in 2012 and 2014, green-up day of year in 2013, anthesis date in 2012, and yield in 2012, they were also subjected to NIR spectroscopy to derive cell wall composition estimates based on prior NIR calibrations. Plants were genotyped via a genotyping by sequencing (GBS) approach from reduced representation libraries constructed with adaptors that identified each individual. Libraries generated with the restriction enzyme PstI and called SNPs using Samtools after alignment to version 1.1 of the switchgrass genome sequence. A total of approximately 40,000 SNPs were found. These were then further filtered to eliminate markers with a minor allele frequency of < 0.05. The results of population analysis using STRUCTURE with expected population sizes or cluster numbers (K), clearly shows the hybrid composition of the KxS population and discriminated easily between upland (Summer) and lowland (Kanlow) populations. Under an assumption of 5 distinct populations there were detectable differences in allele frequencies between subpopulations within the three Kanlow populations particularly with respect to Kanlow EM and Kanlow base. We detected 110 SNPs with an allele frequency difference of ≥ 0.2 between Kanlow EM and Kanlow base populations, while 120 SNPs showed an allele frequency difference of ≥ 0.15 between Kanlow N1 and Kanlow base populations. These data are being readied for publication.
59 BASIC BIOLOGICAL SCIENCES↗
Final technical report for Phenomic Analysis of Natural and Induced Variation in Brachypodium Distachyon DE-SC0001526
The goal of this project was to apply high-throughput, non-destructive phenotyping (phenomics) to collections of natural variants and induced mutants of the model grass Brachypodium distachyon and characterize a small subset of that material in detail. B. distachyon is well suited to this phenomic approach because its small size and rapid generation time allow researchers to grow many plants under carefully controlled conditions. In addition, the simple diploid genetics, high quality genome sequence and existence of numerous experimental tools available for B. distachyon allow us to rapidly identify genes affecting specific phenotypes. Our phenomic analysis revealed great diversity in biofuel-relevant traits like growth rate, biomass and photosynthetic rate. This clearly demonstrated the feasibility of applying a phenomic approach to the model grass B. distachyon. We also demonstrated the utility of B. distachyon for studying mature root system, something that is virtually impossible to do with biomass crops. We showed tremendous natural variation in root architecture that can potentially be used to design crops with superior nutrient and water harvesting capability. Finally, we demonstrated the speed with which we can link specific genes to specific phenotypes by studying two mutants in detail. Importantly, in both cases, the specific biological lessons learned were grass-specific and could not have been learned from a dicot model system. Furthermore, one of the genes affects cell wall integrity and thus may be a useful target in the context of biomass crop improvement. Ultimately, all this information can be used to accelerate the creation of improved biomass crops.
59 BASIC BIOLOGICAL SCIENCES↗
An Integrated Approach to Improving Plant Biomass Production
Developing a sustainable biofuel program that minimizes negative impacts on the environment and captures the maximum usable energy per acre is a major challenge in the 21 st century. This study used rice as a model grass to identify novel biomass genes and to determine natural variation in cell-wall composition given the wide array of rice genomic tools and the ease of genetic manipulation relative to emerging grass bioenergy crops. In rice, we established an efficient pipeline to identify loci for biomass production and composition. From that work, we identified biomass QTL and candidate genes for improving biomass quality and quantity in plants. Then, we developed resources to enhance the translation of information of biomass production from rice to switchgrass, and used these resources to test candidate genes for function in improving biomass production in switchgrass. We created a web based genomics platform to display and facilitate analysis of rice and switchgrass comparative functional and genomic data. Finally, we describe a novel field-level high throughput phenotyping system that allows for efficient, rapid capture of phenotype data, enabling the mapping of biomass QTL in large plant populations during growth and development. Overall, our project contributed (1) valuable genetic and genomic resources and tools in rice and switchgrass to the biomass community, (2) identified key biomass traits that are amenable for improvement by breeding or biotechnology, (3) provided validation that information from model systems could be applied to improvement of bioenergy crops, (4) developed a novel high throughput phenotyping system for field-level discovery of biomass QTL, and (5) contributed to the interdisciplinary training of four post doctoral fellows and five graduate students.
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Use and engineering of efflux pumps for the export of olefins in microbes
The scope of the project is to investigate efflux pump systems in engineered host microorganisms, such as E. coli, and develop a pump engineered to export a target compound. To initiate the project in coordination with other TOTAL driven projects, the first target compound to be studied was 1-hexene. However, we were investigating other chemicals as Styrene. The main goal of the project was to generate a set of optimized efflux pump systems for microorganisms (E. coli and Streptomyces or other host) engineered to contain biosynthetic pathways to export large titers of target compounds that are toxic (or accumulate and push back biosynthesis) to the host cell. An optimized microbial host will utilize specific and efficient cell wall located pumps to extrude harmful target compounds and enable greater production of these compounds.
60 APPLIED LIFE SCIENCES↗
Modulation of phytochrome signaling networks for improved biomass accumulation using a bioenergy crop model
Plant growth and development, including stem elongation, flowering time, and shade-avoidance habits, are affected by wavelength composition (i.e., light quality) of the light environment. the molecular mechanisms underlying light perception and signaling pathways in plants have been best characterized in Arabidopsis thaliana where dozens of genes have been implicated in converging, complementary, and antagonistic pathways communicating light quality cues perceived by the phytochrome (red/far-red) cryptochrome (blue) and phototropin (blue) photorecptors. Light perception and signaling have been studied in grasses, including rice and sorghum but in much less detail than in Arabidopsis. During the course of the Mocker lab's DOE-funded wrok generating a gene expression atlas in Brachypodium distachyon we observed that Brachypodium plants grown in continuous monochromatic red light or continuous white light enriched in far-red light accumulated significantly more biomass and exhibited significantly greater seed yield than plants grown in monochromatic blue light or white light. This phenomenon was also observed in two other grasses, switchgrass and rice. We will systematically manipulate the expression of genes predicted to function in Brachypodium phytochrome signaling and assess the phenotypic consequences in transgenic Brachypodium plants in terms of morphology, stature, biomass accumulation, and cell wall composition. We will also interrogate direct interactions between candidate phytochrome signaling transcription factors and target promoters using a high-throughput yeast one-hybrid system. Brachypodium distachyon has emerged as a model grass species and is closely related to candidate feedstock crops for bioethanol production. Identification of genes capable of modifying growth characteristics of Brachypodium, when misexpressed, in particular increasing biomass accumulation, by modulating photoreceptor signaling will provide valuable candidates for manipulation in biomass and biofuel feedstock grass crops through targeted breeding or engineering efforts.
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