The Class II KNOX gene KNAT7 negatively regulates secondary wall formation in Arabidopsis and is functionally conserved in Populus

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 remain...

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Bibliographic Details
Published in:The New phytologist 2012-04, Vol.194 (1), p.102-115
Main Authors: Li, Eryang, Bhargava, Apurva, Qiang, Weiya, Friedmann, Michael C., Forneris, Natascha, Savidge, Rodney A., Johnson, Lee A., Mansfield, Shawn D., Ellis, Brian E., Douglas, Carl J.
Format: Article
Language:English
Subjects:
Alleles
Arabidopsis
Arabidopsis - cytology
Arabidopsis - genetics
Arabidopsis Proteins - genetics
Arabidopsis Proteins - metabolism
Biosynthesis
Cell Nucleus - metabolism
Cell Wall - metabolism
Cell Wall - ultrastructure
Cell walls
Conserved Sequence
Feedback loops
Fiber cells
Fibers
Gene expression
Gene Expression Profiling
Gene expression regulation
Gene Expression Regulation, Plant
Genes
Genes, Plant - genetics
Genetic Complementation Test
Glucuronidase - metabolism
Green Fluorescent Proteins - metabolism
homeodomain protein
Homeostasis
Inflorescence - metabolism
Inflorescence - ultrastructure
Inflorescences
KNOX gene
Lignin
Lignin - metabolism
Mutagenesis, Insertional - genetics
Mutation - genetics
Negative feedback
Phenotype
Phenotypes
Phylogeny
Plant Stems - anatomy & histology
Plant Stems - metabolism
Plant Stems - ultrastructure
Plants
Plants, Genetically Modified
Poplar
Populus
Populus - genetics
Protein Transport
Real-Time Polymerase Chain Reaction
Renewable energy
repression
Repressor Proteins - genetics
Repressor Proteins - metabolism
secondary cell wall
Sequence Homology, Amino Acid
Stems
Transcription
transcription factor
Wall deposition
Wall thickness
Xylem
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Summary: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.
ISSN:0028-646X
1469-8137
DOI:10.1111/j.1469-8137.2011.04016.x