Bicistronic Expression of Gibberellin 20-Oxidase and Secondary Wall Biosynthetic MYB Transcription Factor Improves Both Quality and Quantity of Woody Biomass Production in Poplar

Research of woody biomass production has increased as a potential renewable resource for biofuel. In this study, we present a novel approach for biotechnological improvement of the quantity and quality of woody biomass with minimizing undesirable growth penalties. We applied a multi-cistronic gene expression system, known as viral 2A peptide, which allows expressing two or more genes under the same promoter, thus capable to express two or more genes at the exactly same spatio-temporal manner. Our transgenic poplars designed to express both GA20-oxidease (a key enzyme to produce bioactive gibberellin (GA)) and a MYB transcription factor involved in secondary wall biosynthesis in developing xylem (DX) tissue-specific, resulted in a biomass increase up to 175%. Similar phenotypes were also observed in the transgenic Arabidopsis plants harboring the same gene construct. This phenotypic consequence was further verified in LMO-field experiment. During three months of actively growing season, our transgenic poplars grow up to 156% and 123% in the height and diameter, respectively, compared to wild-type poplar without any undesirable phenotypes. Our results demonstrate that the controlled production of GAs and secondary wall regulating MYB TF through a DX promoter can be utilized as an efficient biotechnological tool for producing enhanced plant biomass without undesirable side effects. This work was funded by the Basic Science Research Program through the National Research Foundation of Korea (NRF) (2011-0008840) and a grant from the Korea Forest Service (S111213L080110).