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

Wegi A. Wuddineh, Mitra Mazarei, Jiyi Zhang, Charleson R. Poovaiah, David G.J. Mann, Angela Ziebell, Robert W. Sykes, Mark F. Davis, Michael K. Udvardi, Charles Neal Stewart

Research output: Contribution to journalArticleResearchpeer-review

113 Citations (Scopus)

Abstract

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.

Original languageEnglish
Pages (from-to)636-647
Number of pages12
JournalPlant Biotechnology Journal
Volume13
Issue number5
DOIs
Publication statusPublished - Jun 2015
Externally publishedYes

Keywords

  • Biofuel
  • Gibberellin
  • Gibberellin 2-oxidase
  • Lignin
  • Semi-dwarf

Cite this