Dual Utilization of Medicinal and Aromatic Crops as Bioenergy Feedstocks.

Dual production of biofuels and chemicals can increase the economic value of lignocellulosic bioenergy feedstocks. We compared the bioenergy potential of several essential oil (EO) crops with switchgrass ( Panicum virgatum L.), a crop chosen to benchmark biomass and lignocellulosic biofuel production.

Development and use of a switchgrass ( L.) transformation pipeline by the BioEnergy Science Center to evaluate plants for reduced cell wall recalcitrance.

Background: The mission of the BioEnergy Science Center (BESC) was to enable efficient lignocellulosic-based biofuel production. One BESC goal was to decrease poplar and switchgrass biomass recalcitrance to biofuel conversion while not affecting plant growth. A transformation pipeline (TP), to express transgenes or transgene fragments (constructs) in these feedstocks with the goal of understanding and decreasing recalcitrance, was considered essential for this goal.

Transgenic switchgrass (Panicum virgatum L.) targeted for reduced recalcitrance to bioconversion: a 2-year comparative analysis of field-grown lines modified for target gene or genetic element expression.

Transgenic Panicum virgatum L. silencing (KD) or overexpressing (OE) specific genes or a small RNA (GAUT4-KD, miRNA156-OE, MYB4-OE, COMT-KD and FPGS-KD) was grown in the field and aerial tissue analysed for biofuel production traits. Clones representing independent transgenic lines were established and senesced tissue was sampled after year 1 and 2 growth cycles.

Downregulation of a UDP-Arabinomutase Gene in Switchgrass ( L.) Results in Increased Cell Wall Lignin While Reducing Arabinose-Glycans.

Switchgrass ( L.) is a C perennial prairie grass and a dedicated feedstock for lignocellulosic biofuels. Saccharification and biofuel yields are inhibited by the plant cell wall's natural recalcitrance against enzymatic degradation.

Sugarcane transgenics expressing MYB transcription factors show improved glucose release.

Background: Sugarcane, a tropical C4 perennial crop, is capable of producing 30-100 tons or more of biomass per hectare annually. The lignocellulosic residue remaining after sugar extraction is currently underutilized and can provide a significant source of biomass for the production of second-generation bioethanol.

Results: MYB31 and MYB42 were cloned from maize and expressed in sugarcane with and without the UTR sequences.

Engineered selective plant male sterility through pollen-specific expression of the EcoRI restriction endonuclease.

Unintended gene flow from transgenic plants via pollen, seed and vegetative propagation is a regulatory concern because of potential admixture in food and crop systems, as well as hybridization and introgression to wild and weedy relatives. Bioconfinement of transgenic pollen would help address some of these concerns and enable transgenic plant production for several crops where gene flow is an issue. Here, we demonstrate the expression of the restriction endonuclease EcoRI under the control of the tomato pollen-specific LAT52 promoter is an effective method for generating selective male sterility in Nicotiana tabacum (tobacco).

Identification and overexpression of gibberellin 2-oxidase (GA2ox) in switchgrass (Panicum virgatum L.) for improved plant architecture and reduced biomass recalcitrance.

Gibberellin 2-oxidases (GA2oxs) are a group of 2-oxoglutarate-dependent dioxygenases that catalyse the deactivation of bioactive GA or its precursors through 2β-hydroxylation reaction. In this study, putatively novel switchgrass C20 GA2ox genes were identified with the aim of genetically engineering switchgrass for improved architecture and reduced biomass recalcitrance for biofuel. Three C20 GA2ox genes showed differential regulation patterns among tissues including roots, seedlings and reproductive parts.

Transgenic switchgrass (Panicum virgatum L.) biomass is increased by overexpression of switchgrass sucrose synthase (PvSUS1).

Sucrose synthase (SUS) converts sucrose and uridine di-phosphate (UDP) into UDP-glucose and fructose. UDP-glucose is used by the cellulose synthase to produce cellulose for cell wall biosynthesis. For lignocellulosic feedstocks such as switchgrass, the manipulation of cell walls to decrease lignin content is needed to reduce recalcitrance of conversion of biomass into biofuels.

Altered lignin biosynthesis using biotechnology to improve lignocellulosic biofuel feedstocks.

Lignocellulosic feedstocks can be converted to biofuels, which can conceivably replace a large fraction of fossil fuels currently used for transformation. However, lignin, a prominent constituent of secondary cell walls, is an impediment to the conversion of cell walls to fuel: the recalcitrance problem. Biomass pretreatment for removing lignin is the most expensive step in the production of lignocellulosic biofuels.

Enhanced characteristics of genetically modified switchgrass (Panicum virgatum L.) for high biofuel production.

Background: Lignocellulosic biomass is one of the most promising renewable and clean energy resources to reduce greenhouse gas emissions and dependence on fossil fuels. However, the resistance to accessibility of sugars embedded in plant cell walls (so-called recalcitrance) is a major barrier to economically viable cellulosic ethanol production. A recent report from the US National Academy of Sciences indicated that, "absent technological breakthroughs", it was unlikely that the US would meet the congressionally mandated renewable fuel standard of 35 billion gallons of ethanol-equivalent biofuels plus 1 billion gallons of biodiesel by 2022.

Functional characterization of the switchgrass (Panicum virgatum) R2R3-MYB transcription factor PvMYB4 for improvement of lignocellulosic feedstocks.

• The major obstacle for bioenergy production from switchgrass biomass is the low saccharification efficiency caused by cell wall recalcitrance. Saccharification efficiency is negatively correlated with both lignin content and cell wall ester-linked p-coumarate: ferulate (p-CA : FA) ratio. In this study, we cloned and functionally characterized an R2R3-MYB transcription factor from switchgrass and evaluated its potential for developing lignocellulosic feedstocks.

Gateway-compatible vectors for high-throughput gene functional analysis in switchgrass (Panicum virgatum L.) and other monocot species.

Switchgrass (Panicum virgatum L.) is a C4 perennial grass and has been identified as a potential bioenergy crop for cellulosic ethanol because of its rapid growth rate, nutrient use efficiency and widespread distribution throughout North America. The improvement of bioenergy feedstocks is needed to make cellulosic ethanol economically feasible, and genetic engineering of switchgrass is a promising approach towards this goal.