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. Using a transgenic approach, we showed that overexpression of two C20 GA2ox genes, that is PvGA2ox5 and PvGA2ox9, resulted in characteristic GA-deficient phenotypes with dark-green leaves and modified plant architecture. The changes in plant morphology appeared to be associated with GA2ox transcript abundance. Exogenous application of GA rescued the GA-deficient phenotypes in transgenic lines. Transgenic semi-dwarf lines displayed increased tillering and reduced lignin content, and the syringyl/guaiacyl lignin monomer ratio accompanied by the reduced expression of lignin biosynthetic genes compared to nontransgenic plants. A moderate increase in the level of glucose release in these transgenic lines might be attributed to reduced biomass recalcitrance as a result of reduced lignin content and lignin composition. Our results suggest that overexpression of GA2ox genes in switchgrass is a feasible strategy to improve plant architecture and reduce biomass recalcitrance for biofuel.
Department of Plant Sciences, University of Tennessee, Knoxville, TN 37996, USA.|Bioenergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
Wegi A
WA
Wuddineh
Department of Plant Sciences, University of Tennessee, Knoxville, TN 37996, USA.|Bioenergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
Mitra
M
Mazarei
Bioenergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.|Plant Biology Division, Samuel Roberts Noble Foundation, Ardmore, OK 73401, USA.
Jiyi
J
Zhang
Department of Plant Sciences, University of Tennessee, Knoxville, TN 37996, USA.|Bioenergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
Charleson R
CR
Poovaiah
Department of Plant Sciences, University of Tennessee, Knoxville, TN 37996, USA.|Bioenergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
David G J
DG
Mann
Bioenergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.|National Renewable Energy Laboratory, Golden, CO 80401, USA.
Angela
A
Ziebell
Bioenergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.|National Renewable Energy Laboratory, Golden, CO 80401, USA.
Robert W
RW
Sykes
Bioenergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.|National Renewable Energy Laboratory, Golden, CO 80401, USA.
Mark F
MF
Davis
Bioenergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.|Plant Biology Division, Samuel Roberts Noble Foundation, Ardmore, OK 73401, USA.
Michael K
MK
Udvardi
Department of Plant Sciences, University of Tennessee, Knoxville, TN 37996, USA.|Bioenergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
Charles Neal
CN
Stewart
D056804:Biofuels; D018533:Biomass; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D007656:Ketoglutaric Acids / Q000378:metabolism; D008031:Lignin / Q000378:metabolism*; D006899:Mixed Function Oxygenases / Q000235:genetics* / Q000378:metabolism; D008897:Panicum / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D010641:Phenotype; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D036226:Seedlings / Q000201:enzymology / Q000235:genetics / Q000254:growth & development
D056804:Biofuels; D007656:Ketoglutaric Acids; D010940:Plant Proteins; D008031:Lignin; D006899:Mixed Function Oxygenases; C121463:gibberellin 2-dioxygenase
biofuel; gibberellin; gibberellin 2-oxidase; lignin; semi-dwarf