GLBRC's Publications


Our researchers consistently turn out new and innovative research that can lead to publications and new technology. On this page we'll highlight new research publications and/or activities in the GLBRC that underscore the great work that our researchers are doing.

The degradation of cellulose, the principal component of plant cell walls, is critical to ecosystem functioning and the global carbon cycle. The primary drivers of plant biomass deconstruction are fungi and bacteria found in the soil or associated with plant-eating eukaryotes. 

Native perennial grasslands, which can be planted on marginal lands, are a potential feedstock source for lignocellulosic biofuel production. And yet more information is needed to understand how management practices such as frequency or timing of harvesting can affect their productivity and community composition.

By studying a naturally silenced maize mutant defective in chalcone synthase, a key enzyme involved in the biosynthesis of flavonoids, we demonstrated that levels of tricin-related flavonoids were significantly reduced, resulting in strongly reduced incorporation of tricin into the lignin polymer. These plants also had increased total lignin content and, consequently, demonstrated significantly reduced saccharification.

Adding cover crops to annual maize production systems did not enhance predator communities. And predation levels remained low in comparison to perennial bioenergy crops. 

OptSSeq (Optimization by Selection and Sequencing) is a newly developed approach to identifying optimally balanced enzyme levels in synthetic biofuel production pathways. This method couples selection of enzyme expression levels with high-throughput gene sequencing to track enrichment of gene expression elements from a combinatorial library.    

To explore the genetic architecture of flowering time, we developed a recombinant inbred line population from a cross between two diverse accessions of the grass Brachypodium distachyon that have different flowering behavior. We then used a genotyping-by-sequencing approach to identify six quantitative trait locis that control differences in flowering time.

We performed genome-wide association studies to characterize the genetic architecture and genes underlying flowering time regulation in switchgrass. We then identified association with flowering time at multiple loci, including in a homolog of the gene FLOWERING LOCUS T and in a locus containing the gene TIMELESS, a homolog of a key circadian regulator in animals.

We collected sorghum stem RNA-seq transcriptome profiles and composition data for approximately 100 days of development beginning at floral initiation. Our analysis identified more than 200 differentially expressed genes involved in stem growth, cell wall biology, and sucrose accumulation.

The production of fuels from lignocellulosic biomass can play an important role in reducing our dependence on fossil fuels while meeting an increasing energy demand. In an effort to meet these goals, regional biomass processing depots have been introduced as a way to improve the biomass supply network.

Excess sugars made during periods of drought are converted to inhibitors during biomass pretreatment.

The electrochemical oxidation of alcohols is a major focus of energy and chemical conversion efforts, with potential applications ranging from fuel cells to biomass utilization and chemical synthesis. 

Formaldehyde addition during biomass pretreatment leads to near-theoretical yields of lignin monomers.  

A stress-tolerant yeast strain was evolved for enhanced xylose utilization under aerobic or anaerobic growth conditions, the causative mutations identified by whole-genome sequencing, and systems-level effects of the mutations on cellular metabolism were analyzed. Rapid xylose utilization was found to be dependent upon genetic interactions among four genes, uncovering a surprising connection between Fe-S cluster assembly and cell signaling that facilitates aerobic respiration and anaerobic fermentation of xylose. 

With a sensitive analytical method for diagnostically detecting incorporation of chemically labile ester bonds introduced into lignin polymers by augmenting the prototypical monomers with monolignol ferulate conjugates (“zip monomers”), we reexamined the lignin of three plants known to produce such conjugates in their extractives and found that these plants also used monolignol ferulate conjugates in their lignification. This discovery prompted a survey of a set of plants representing spermatophytes or “seed plants,” including 13 gymnosperms and 54 angiosperms.  

We measured soil N2O emissions, CH4 uptake, NO3- leaching, and soil organic carbon accumulation for switchgrass under various N fertilizer rates over a three-year period after establishment. We found for annual N2O emissions by fertilizer rate an exponential increase that was stronger every year, and also that switchgrass yields became less responsive each year to N fertilizer. Nitrate leaching also increased exponentially in response to added N, but methane uptake and soil organic carbon didn’t change detectably. Overall, N fertilizer inputs at rates greater than crop need curtailed the climate benefit of ethanol production almost two-fold, from a maximum mitigation capacity of −5.71 ± 0.22 Mg CO2e ha−1 yr−1 in switchgrass fertilized at 56 kg N ha−1 to only −2.97 ± 0.18 Mg CO2e ha−1 yr−1 in switchgrass fertilized at 196 kg N ha−1. Minimizing N fertilizer use will be an important strategy for fully realizing the climate benefits of cellulosic biofuel production.

The flowering of many plant species is coordinated with seasonal environmental cues such as temperature and photoperiod. In winter wheat and barley, three genes – VRN1, VRN2, and FT – form a regulatory loop that regulates the initiation of flowering. Here, we test whether the circuitry of this regulatory loop is conserved across Pooid grasses. Our studies reveal that some aspects of the regulatory loop, such as the cold repression of VRN2, are unique to wheat and barley. However, this study, as well some of our previous work, demonstrates that VRN2 is a repressor of flowering that functions broadly in grasses from rice to Brachypodium, and thus VRN2 is a target for fine tuning of flowering in grass biofuel crops. 

This study assessed the possibility of producing reliable predictions for genomic selection using a small sample size of two different switchgrass populations genotyped by exome sequencing and tested in two different locations for three important agronomic traits: biomass yield, plant height, and heading date (flowering time). We assessed various prediction procedures, differing by prediction model and also by type of marker-data transformation. 

This study aimed to elucidate the incorporation pathways of tricin into maize lignin by applying liquid chromatography-mass spectrometry-based tools developed for oligolignol profiling. Twelve tricin-containing products (each with up to eight isomers) were observed and authenticated by comparisons with a set of synthetic tricin-oligolignol dimeric and trimeric compounds. 

As a feedstock for biomass-to-biofuel processes, woody biomass exhibits several advantages that facilitate logistics relative to herbaceous feedstocks, including year-round availability and high bulk density. As we envision biomass-to-biofuel processes that include diverse biomass feedstocks, the physical and chemical properties of said biomass will have an important impact on the conversion process.   

Lignocellulosic crop residues are a promising alternative feedstock for producing liquid fuels and chemicals for modern biobased economies, and biochemical conversion of lignocellulosic biomass to liquid fuels requires pretreatment and enzymatic hydrolysis of the biomass to yield fermentable sugars. To compete with traditional refineries, biorefineries must achieve high carbohydrate-to-fuel yields with low enzymatic input and facilitate lignin valorization to co-products extending beyond simply using lignin to generate heat and power. Most pretreatment processes require high enzymatic loadings to achieve higher sugar yields under industrially-relevant conditions.