Manipulation of Guaiacyl and Syringyl Monomer Biosynthesis in an Arabidopsis Cinnamyl Alcohol Dehydrogenase Mutant Results in Atypical Lignin Biosynthesis and Modified Cell Wall Structure.
Modifying lignin composition and structure is a key strategy to increase plant cell wall digestibility for biofuel production. Disruption of the genes encoding both cinnamyl alcohol dehydrogenases (CADs), including CADC and CADD, in Arabidopsis thaliana results in the atypical incorporation of hydroxycinnamaldehydes into lignin. Another strategy to change lignin composition is downregulation or overexpression of ferulate 5-hydroxylase (F5H), which results in lignins enriched in guaiacyl or syringyl units, respectively. Here, we combined these approaches to generate plants enriched in coniferaldehyde-derived lignin units or lignins derived primarily from sinapaldehyde. The cadc cadd and ferulic acid hydroxylase1 (fah1) cadc cadd plants are similar in growth to wild-type plants even though their lignin compositions are drastically altered. In contrast, disruption of CAD in the F5H-overexpressing background results in dwarfism. The dwarfed phenotype observed in these plants does not appear to be related to collapsed xylem, a hallmark of many other lignin-deficient dwarf mutants. cadc cadd, fah1 cadc cadd, and cadd F5H-overexpressing plants have increased enzyme-catalyzed cell wall digestibility. Given that these CAD-deficient plants have similar total lignin contents and only differ in the amounts of hydroxycinnamaldehyde monomer incorporation, these results suggest that hydroxycinnamaldehyde content is a more important determinant of digestibility than lignin content.
Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907 Heartland Plant Innovations, Manhattan, Kansas 66502.
Nickolas A
http://orcid.org/0000-0002-6572-8954
NA
Anderson
Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706 DOE Great Lakes Bioenergy Research Center and Wisconsin Energy Institute, University of Wisconsin-Madison, Madison, Wisconsin 53726 Research Institute for Sustainable Humanosphere, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan.
Yuki
Y
Tobimatsu
Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401.
Peter N
PN
Ciesielski
Department of Agricultural and Biological Engineering and the Laboratory of Renewable Resources Engineering, Purdue University, West Lafayette, Indiana 47907.
Eduardo
http://orcid.org/0000-0001-9087-0218
E
Ximenes
Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706 DOE Great Lakes Bioenergy Research Center and Wisconsin Energy Institute, University of Wisconsin-Madison, Madison, Wisconsin 53726 Department of Biological Systems Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706.
John
J
Ralph
Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401.
Bryon S
http://orcid.org/0000-0002-2272-5059
BS
Donohoe
Department of Agricultural and Biological Engineering and the Laboratory of Renewable Resources Engineering, Purdue University, West Lafayette, Indiana 47907 Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana 47907.
Michael
http://orcid.org/0000-0001-9953-9599
M
Ladisch
Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907 chapple@purdue.edu.
Clint
http://orcid.org/0000-0002-5195-562X
C
Chapple
D000429:Alcohol Oxidoreductases / Q000235:genetics* / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002473:Cell Wall / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D002934:Cinnamates / Q000737:chemistry / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D008031:Lignin / Q000096:biosynthesis* / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D018613:Microscopy, Confocal; D046529:Microscopy, Electron, Transmission; D008956:Models, Chemical; D015394:Molecular Structure; D009154:Mutation; D030821:Plants, Genetically Modified
D029681:Arabidopsis Proteins; D002934:Cinnamates; C434470:guaiacyl monolignol; C117045:p-hydroxycinnamaldehyde; C434469:syringyl monolignol; D008031:Lignin; D003577:Cytochrome P-450 Enzyme System; D000429:Alcohol Oxidoreductases; C520968:CAD4 protein, Arabidopsis; C520967:CAD5 protein, Arabidopsis; C097486:CYP84A1 protein, Arabidopsis