Biomass conversion: opportunities in lignin management Clint Chapple Department of Biochemistry Purdue University
Targets for biomass improvement Yield Water and nutrient use efficiency Pest and pathogen resistance Biomass quality
Targets for biomass improvement Yield Water and nutrient use efficiency Pest and pathogen resistance Biomass quality
Lignin is critical for plant survival structural support water transport important impact on bioenergy and bioprocessing large commitment of fixed carbon high energy density
Lignin is a biosynthetically plastic polymer Bonawitz and Chapple, Ann Rev Genetics, 2010
Lignin is a biosynthetically plastic polymer Nucleic acid synthesis Template-dependent Protein synthesis Template-dependent H H Me H H H Me Me H H Me Me H Me H Me H Me Polysaccharide synthesis Me Enzyme specificity-directed H Me H H H Lignin synthesis Random radical coupling dependent on precursor supply
pportunities for lignin engineering Block lignin synthesis Change lignin composition Redirect lignin monomers Alter lignin localization
Mutant screens can identify genes important to processes of interest Normal plant mutagenesis Mutant with trait of interest gene identification Understanding of gene function
Lignin is a biosynthetically plastic polymer Bonawitz and Chapple, Ann Rev Genetics, 2010
Lignin modification-induced dwarfing (LMID) Schilmiller et al., Plant J. 2009
Lignin is a biosynthetically plastic polymer Bonawitz and Chapple, Ann Rev Genetics, 2010
Lack of C3'H reduces lignin content and leads to novel lignins Franke et al., Plant J, 2002
Lignin is a biosynthetically plastic polymer Bonawitz and Chapple, Ann Rev Genetics, 2010
ref4 and rfr1 are required for lignin regulation
ref4 and rfr1 are required for lignin regulation
REF4 and RFR1 are components of the Mediator complex P Cramer Lab, Gene Center, University of Munich
Disruption of MED5 rescues the dwarf phenotype of ref8 wild type Bonawitz et al., Nature, 2014 med5a/b ref8-1 med5a/b ref8-1 ref8-2 med5a/b ref8-2
ref8-1 mutants show widespread MED5-dependent transcriptional reprogramming med5a/b 89 39 ref8-1 4441 med5a/b 19 12 ref8-1 3360 95 54 25 430 47 371 216 med5a/b ref8-1 196 med5a/b ref8-1 up-regulated down-regulated (DeSeq, false discovery rate <0.05) Bonawitz et al., Nature, 2014
med5a/b ref8-1 mutants synthesize predominantly H lignin wild type med5a/b med5a/b ref8-1 syringyl (S) guaiacyl (G) p-hydroxyphenyl (H) Yuki Tobimatsu, John Ralph, Wisconsin
med5a/b ref8 mutants show facilitated saccharification 100 no pretreatment 100 liquid hot water pretreated glucose release (%) 80 60 40 20 80 60 40 20 wild type med5a/b med5a/b ref8-1 0 0 0 24 48 72 0 24 48 72 time (hrs) Eduardo Ximenes, Mike Ladisch, Purdue
Suppressor screens can identify genes important to processes of interest Normal plant mutagenesis Mutant with trait of interest mutagenesis Mutant plant in which trait is abolished
Suppressors of ref4-3 may identify other proteins required for phenylpropanoid regulation Dolan et al., unpublished
Whole genome sequencing identified intragenic suppressor mutations and Mediator subunit suppressors Dolan et al., unpublished
REF4 and RFR1 are components of the Mediator complex P Cramer Lab, Gene Center, University of Munich
Maybe lignin isn t all bad Significant proportion of plant biomass More highly reduced than sugars and polysaccharides Amenable to catalytic degradation and conversion H H Me H Me H H Me Me H H Me Me H H Me H H Me H Me H H Me
Parsell et al., Green Chemistry 2015 Maybe lignin isn t all bad
Shuai et al., Science 2016 Maybe lignin isn t all bad
Summary We are developing an understanding of the catalysts and regulators that provide us with control over lignin The study of Arabidopsis has revealed a previously unknown regulatory circuit for lignin biosynthesis that involves Mediator The dwarfing seen in some lignin-deficient plants can be suppressed genetically, indicating that it is an active proteinmediated process Plants with high H-lignin are viable and could provide novel inputs for the biorefinery Catalytic conversion of lignin into fuels may make more efficient use of biomass
Acknowledgements Purdue and C3Bio Nick Bonawitz Whitney Dolan Jake Stout Candy Mao Bryon Donohoe Peter Ciesielski Eduardo Ximenes Mike Ladisch GCEP Sirius Li Yuki Tobimatsu John Ralph Chris McClellan Claire Halpin Wout Boerjan Brian Dilkes Charles Addo-Quaye