Abstract
BackgroundSwitchgrass (Panicum virgatum L.) has a great potential as a platform for the production of biobased plastics, chemicals and energy mainly because of its high biomass yield on marginal land and low agricultural inputs. During the last decade, there has been increased interest in the genetic improvement of this crop through transgenic approaches. Since switchgrass, like most perennial grasses, is exclusively cross pollinating and poorly domesticated, preventing the dispersal of transgenic pollen into the environment is a critical requisite for the commercial deployment of this important biomass crop. In this study, the feasibility of controlling pollen-mediated gene flow in transgenic switchgrass using the large serine site-specific recombinase Bxb1 has been investigated.ResultsA novel approach utilizing co-transformation of two separate vectors was used to test the functionality of the Bxb1/att recombination system in switchgrass. In addition, two promoters with high pollen-specific activity were identified and thoroughly characterized prior to their introduction into a test vector explicitly designed for both autoexcision and quantitative analyses of recombination events. Our strategy for developmentally programmed precise excision of the recombinase and marker genes in switchgrass pollen resulted in the generation of transgene-excised progeny. The autoexcision efficiencies were in the range of 22-42% depending on the transformation event and assay used.ConclusionThe results presented here mark an important milestone towards the establishment of a reliable biocontainment system for switchgrass which will facilitate the development of this crop as a biorefinery feedstock through advanced biotechnological approaches.
Highlights
Switchgrass (Panicum virgatum L.) has a great potential as a platform for the production of biobased plastics, chemicals and energy mainly because of its high biomass yield on marginal land and low agricultural inputs
We have investigated the feasibility of engineering site-specific autoexcision of transgenes in switchgrass pollen mediated by the large serine recombinase Bxb1
Bxb1/att recombination system is functional in switchgrass A gain-of-function strategy was used to test the Bxb1/att site-specific recombination system in switchgrass
Summary
Switchgrass (Panicum virgatum L.) has a great potential as a platform for the production of biobased plastics, chemicals and energy mainly because of its high biomass yield on marginal land and low agricultural inputs. Switchgrass (Panicum virgatum L.), a warm-season perennial grass native to North America, is recognized as a premium candidate and has been identified by the U.S Department of Energy as a model herbaceous energy crop due to its potential for high biomass production on marginal land, low agricultural inputs and positive environmental impacts [3]. Traditional breeding efforts have been focused on the improvement of switchgrass as a forage crop [4], while the current bioenergy research is targeting high cellulose and starch content for bioethanol production and low ash content for combustion systems [5] combined with significantly increased biomass yield. The recently demonstrated potential of switchgrass as a production platform for PHA bioplastics and biochemicals [6,7] makes this crop a promising candidate for the development of a value added biorefinery feedstock for the production of biobased coproducts and energy [8]
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