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Challenges and advances in biotechnology for trees and forests
Coming soon to a forest near youThe Marcus Wallenberg Prize Symposium
27 October 2017Stockholm, Sweden
Ronald SederoffJack Wang, and Vincent ChiangNorth Carolina State University
What gene technology means for the future of forest trees
• Directed modification of wood properties• Accelerated breeding and domestication by genomic selection
• Improved bioenergy and biofuel feedstocks• Manipulation of dominant species of ecosystems
• Reduction of threats from climate change
Barriers to progressPublic opposition (30 years since first GM
tree, but limited deployment)• Fundamental information missing, e.g. epigenetics, what makes a tree, a tree, etc.
• Transformation and regeneration technology not yet adequate for many species.
Modification of wood properties• Wood is one of the worlds’ most important raw materials.
• It will become increasingly difficult to obtain wood as needed for solid wood, fuel and fiber.
• It will also become increasingly difficult to conserve biodiversity, maintain ecosystems, maintain our water supply, and at the same time, provide food and land for an increasing population.
Trees are in the earliest stages of domestication
• Selecting or modifying clones could lead to greater efficiencies or specialized products.
• Greater yields of specialized trees would allow growth of more wood on less land.
• Climate change reduces biodiversity• One strategy is to modify wood for specific processing or end uses.
• One major target has been modification of lignin.
Lignin is a major component of the wood cell wall
Cellulose is the major component of the wood cell wall, about 45%
Lignin is 25 to 30 %
Hemicelluloses(e.g. xylans, or mannans) about 25%
Extractives 3%
From Cote From Lloyd and Donaldson
Conifer wood
More About Lignin
• Lignin affects wood cell wall structure, plant growth, defense and stress responses.
• Understanding lignin has practical value for utilization, processing and modification of wood.
• Lignin has important ecological and evolutionary roles for soils, forests and the atmosphere.
The “take home lessons” Lignin precursor biosynthesis is a strong predictor of wood properties in Populustrichocarpa
Variation in lignin content and composition has unexpected effects on chemical and physical properties of wood and can account for a large fraction of the variation for some traits.
Wang, J.P. et al. Improving wood properties for wood utilization through multi-omic integration in lignin biosynthesis. Submitted.
Jack Wang Vincent Chiang
It is now possible to predict and modify the expression of any monolignol gene or combination of genes, to optimize the effect on tree growth, wood density, mechanical strength, and efficiency of saccharification.
Monolignol biosynthesis in Populus trichocarpa21 core genes, 37 enzymatic steps, 24 metabolites,
three monolignol products
Vincent Chiang
Populus trichocarpa
A systems approach to monolignol biosynthesis(Think like a chemical engineer)
Objective: Construct a predictive mathematical model– Clone each of 21 functional gene models: GENOMICS– Characterize each enzyme, kinetic and inhibition parameters:
ENZYMOLOGY– Quantitate: transcript, protein, metabolite, lignin : BIOCHEMISTRY– Verify with multilevel transgenic suppression: TRANSGENIC
VERIFICATION– QUANTITATION of transgenics by RNA seq; proteomics, enzyme
activity, metabolites, lignin linkages.– Use statistics and computational tools MULTIVARIATE ANALYSIS– SYSTEMS MODELING
Ron SederoffForest Biotech
Vincent ChiangForest Biotech
John Ralph Wisc/Biochemistry
Cranos WilliamsComputer Eng
Joel DucosteCivil Eng
David MuddimanChemistry
Fikret IsikTree Breeding
Hou‐min ChangWood and Paper Sci
Understanding complexity requires mathematical models
The lignin biosynthetic pathway is sufficiently complex that its response to variation is not intuitive. A mathematical model is required to predict its behavior.
Predicting behavior requires identification of components, quantitative abundance estimates and evidence for quantitative response variation.
The model
• We have created an integrated mathematical model based on 84 equations, biochemical quantification of intermediates and ~ 2000 transgenic plants, perturbed in each gene of the monolignol biosynthetic pathway.
Jack Wang
Activity and inhibition constants for 207 kinetic parameters
Wang et al. 2014 Plant Cell.
(Whittman et al., 2009 BMC Systems Biology 2009, 3:98)
Ordinary differential equations (ODEs) can describe the quantitative responses of individual steps in a simple model.
Modeling individual stepsOrdinary differential equations (ODEs)can describe the quantitative responsesof individual steps in a simple model.
Some things I did not tell you• Laser capture microdissection and RNAseqwere used to establish which genes were expressed in the same cell types.
• For some proteins, post translational modificationsmay have a regulatory role – (e.g. OMT is turned off by phosphorylation).
Some protein‐protein interactions have been incorporated into the model.
• Off target effects suggest a higher level of regulation.
Predictive Kinetic Metabolic Flux (PKMF) model of monolignol biosynthesis in P. trichocarpa
From Jack Wang and Punith NaikWang, Naik, et al. Plant Cell 2014
Jack Wang
Punith Niak
Extending the model to the genome
Each transcript produces about 104 molecules of protein. The efficiency of translation is known for each protein.
Putting it all together
• 84 equations link the monolignol genes, proteins, fluxes and metabolites to wood properties.
• Therefore, it is possible to predict the effect of increasing or decreasing the expression of any gene on many chemical and physical properties of wood.
How is this useful?
• Equations may guide strategic engineering of wood properties.
• Correlate lignin products with wood properties, such as saccharification, density or mechanical strength.
• Some conclusions are unexpected.• Can design wood properties from single gene or combinations of gene perturbations.
• Multiple predicted properties can be optimized.
A few inferences• For every 1% reduction in lignin, carbohydrate increases 0.8%
• Plant growth can be independent of lignin content.
• Stiffness of wood is substantially affected by lignin subunits. Reduced lignin reduces stiffness.
• Wood density and stiffness are positively correlated.
• Lignin reduction can greatly increase saccharification efficiency of wood with or without pretreatment.
Wang et al. submitted
What is missing?
• Are all components accounted for?• What about transport, storage and polymerization?
• Are all interactions represented?• Regulation by transcription factors • How general is the model?• What was the evolution of the pathway?• How did it get to be that way?
Lignin, the videogame
• Start with a mathematical model of all steps in the pathway.
• Construct an interactive computer program including all components.
• Manipulate the amounts of any component
• Predict the metabolic products, and the structure of the resulting lignin polymer for specific lignin properties.
Systems biology for forest trees
Cells and organisms are machines that can be described by predictive mathematical models.
New tools are needed to acquire the information in a shorter time. What we now know took the greater part of a decade and many talented people (~51).
Is it “high input, low output”? Yes, somewhat, but it is necessary.
AcknowledgmentsChemistry, NCSU
David MuddimanChris ShufordPhillip LosiukAngelito NepomucinoZhichang YangEmine Gokce
Engineering, NCSUCranos WilliamsJoel DucosteMegan MathewsJina SongPunith Naik
Biochemistry, WisconsinJohn RalphHoon Kim
Michigan TechHairong WeiSapna Kumari
Forest Biomaterials, NCSU Hou-min ChangEwellyn CapanemaIlona PeszlenZach MillerCharles Edmunds
Forestry, NCSUFikret Isik
Forest Biotech NCSUVincent L. ChiangRonald SederoffJack P. Wang Ying‐Chung Lin, Ying‐Hsuan Sun Chien‐Yuan Lin Hsi‐Chuan Chen Quanzi Li Rui Shi Jie LiuSermsawatTunlaya‐AnukitWei LiHao ChenShanfa LuChenmin YangTing‐Feng YehChris SmithChangcao PengPeng ShuaiJidong LiLing ChuangBingyu ZhangYung‐Yun Huang
National Taiwan UniversityMao-Ju Chang
Chinese Academy of Medical Sciences
Jingyuan Song
NE Forestry University, HarbinGuanzheng QuYi Sun
National Bioenergy Center COErica GjersingTodd ShollenbergerMark Davis
Beihua UniversityBao-Guang Liu
Tack så mycket