title: The Class II KNOX gene KNAT7 negatively regulates secondary wall formation in Arabidopsis and is functionally conserved in Populus.
abstract: • The formation of secondary cell walls in cell types such as tracheary elements and fibers is a defining characteristic of vascular plants. The Arabidopsis transcription factor KNAT7 is a component of a transcription network that regulates secondary cell wall biosynthesis, but its function has remained unclear. • We conducted anatomical, biochemical and molecular phenotypic analyses of Arabidopsis knat7 loss-of-function alleles, KNAT7 over-expression lines and knat7 lines expressing poplar KNAT7. • KNAT7 was strongly expressed in concert with secondary wall formation in Arabidopsis and poplar. Arabidopsis knat7 loss-of-function alleles exhibited irregular xylem phenotypes, but also showed increased secondary cell wall thickness in fibers. Increased commitment to secondary cell wall biosynthesis was accompanied by increased lignin content and elevated expression of secondary cell wall biosynthetic genes. KNAT7 over-expression resulted in thinner interfascicular fiber cell walls. • Taken together with data demonstrating that KNAT7 is a transcriptional repressor, we hypothesize that KNAT7 is a negative regulator of secondary wall biosynthesis, and functions in a negative feedback loop that represses metabolically inappropriate commitment to secondary wall formation, thereby maintaining metabolic homeostasis. The conservation of the KNAT7 regulatory module in poplar suggests new ways to manipulate secondary cell wall deposition for improvement of bioenergy traits in this tree.
authors.affiliation: Department of Botany, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4.
authors.forename: Eryang
authors.initials: E
authors.lastname: Li
authors.affiliation: Department of Botany, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4.|Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4.
authors.forename: Apurva
authors.initials: A
authors.lastname: Bhargava
authors.affiliation: Department of Botany, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4.|School of Life Science, Lanzhou University, 730000 Lanzhou, Gansu, China.
authors.forename: Weiya
authors.initials: W
authors.lastname: Qiang
authors.affiliation: Department of Botany, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Friedmann
authors.affiliation: Faculty of Forestry & Environmental Management, University of New Brunswick, Fredericton, NB, Canada, E3B 6C2.
authors.forename: Natascha
authors.initials: N
authors.lastname: Forneris
authors.affiliation: Faculty of Forestry & Environmental Management, University of New Brunswick, Fredericton, NB, Canada, E3B 6C2.
authors.forename: Rodney A
authors.initials: RA
authors.lastname: Savidge
authors.affiliation: Department of Botany, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4.
authors.forename: Lee A
authors.initials: LA
authors.lastname: Johnson
authors.affiliation: Department of Wood Science, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4.
authors.forename: Shawn D
authors.initials: SD
authors.lastname: Mansfield
authors.affiliation: Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4.
authors.forename: Brian E
authors.initials: BE
authors.lastname: Ellis
authors.affiliation: Department of Botany, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4.
authors.forename: Carl J
authors.initials: CJ
authors.lastname: Douglas
mesh_terms: D000483:Alleles; D017360:Arabidopsis / Q000166:cytology* / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism* / Q000648:ultrastructure; D017124:Conserved Sequence; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics*; D005816:Genetic Complementation Test; D005966:Glucuronidase / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D056626:Inflorescence / Q000378:metabolism / Q000648:ultrastructure; D008031:Lignin / Q000378:metabolism; D016254:Mutagenesis, Insertional / Q000235:genetics; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D010802:Phylogeny; D018547:Plant Stems / Q000033:anatomy & histology / Q000378:metabolism / Q000648:ultrastructure; D030821:Plants, Genetically Modified; D032107:Populus / Q000235:genetics*; D021381:Protein Transport; D060888:Real-Time Polymerase Chain Reaction; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D029681:Arabidopsis Proteins; C572748:KNAT7 protein, Arabidopsis; D012097:Repressor Proteins; D049452:Green Fluorescent Proteins; D008031:Lignin; D005966:Glucuronidase