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Kyung-Hwan Han 

Department of Horticulture and Department of Forestry Michigan State University

Sponsored by the Department of Biological Sciences and Life Sciences Technology Institute

Targeted regulation of woody biomass formation: EliteTree Technology
 

Abstract:  Many agricultural and forest lands, which have become economicaly marginal and fallen out of production, have the potential to be replanted to produce significant crops of short rotation woody biomaterials. With genetically designed planting stock, such woody biomaterials could lead to the development of new industries based on cellulose nanocrystals, wood-derived composite, and biofuels. Maximizing yield and modifying the chemical composition of the biomaterials being produced are essential in realizing this potential and making the biomaterials plantations an economically viable alternative to other land uses. We are developing a biotechnological means to genetically control key pathways that determine the quantity and quality of the biomass based on the characteristics that best suit its end-use. Secondary walls constitute the majority of plant biomass. A transcription factor MYB46 functions as a central regulator of secondary wall biosynthesis in Arabidopsis thaliana. Recently, we have found that MYB46 directly regulates the expression of all of the three cellulose synthases (CESA4, CESA7 and CESA8) that are necessary for secondary wall in Arabidopsis plants. We hypothesize that upregulation of MYB46 will increase biomass accumulation in poplar. However, constitutive overexpression of MYB46 results in a growth penalty. We reason that the detrimental growth effect is caused by ectopic lignification in parenchymatous and photosynthetic cells, where no endogenous MYB46 is expressed. We hypothesize that wood-specific upregulation of MYB46 will increase woody biomass accumulation without the growth penalty. Gibberellins (GAs) are involved in many aspects of plant development, including shoot growth and wood formation. Gibberellin 20-oxidase catalyzes consecutive steps of oxidation in the latter part of the GA biosynthetic pathway, thus increasing levels of bioactive GAs. Transgenic overexpression of GA20-oxidase substantially increased plant height growth and biomass accumulation in plants. We hypothesize that wood-specific co-expression of MYB46 with a GA20-oxidase will increase secondary growth and thereby increase biomass production. 
This presentation will discuss the functional consequences of the genetic manipulations on woody biomass formation in poplar